and automatic sun/sky/polarized/lunar photometers, **documenting the quality of the measurements**, and providing all results to the ACTRIS Data Centre, in order to allow the traceability of the ACTRIS data which are made available through the ACTRIS data portal

The Centre for Aerosol Remote Sensing is responsible for **developing and testing new retrieval algorithms or tools** for producing level 1 to 3 data, including the exploitation of instrument synergies

high- and low-power aerosol lidars and automatic sun/sky/polarized/lunar photometers, which are made available through the ACTRIS data portal. Results of quality assurance procedures applied by the Centre for Aerosol Remote Sensing will be traced into the data products.

ACTRIS Data Centre is responsible for **implementing the approved retrieval algorithms or tools** into the ACTRIS Data Centre operation

The workflow between the ACTRIS NFs, the Centre for Aerosol Remote Sensing and the ACTRIS Data Centre is described in the diagrams below, for each component:

### 8.2.2.1 Aerosol high-power lidar (AHL)

<figure><img src="image_14.png" /></figure>

**Note:** Processing of the high-power aerosol lidar data is done at the ACTRIS DC. Aerosol remote sensing NFs should transfer level 0 data directly to the DC. CARS should transfer the results of QA procedures in machine readable format to the ACTRIS DC.
and automatic sun/sky/polarized/lunar photometers, **documenting the quality of the measurements**, and providing all results to the ACTRIS Data Centre, in order to allow the traceability of the ACTRIS data which are made available through the ACTRIS data portal

The Centre for Aerosol Remote Sensing is responsible for **developing and testing new retrieval algorithms or tools** for producing level 1 to 3 data, including the exploitation of instrument synergies

high- and low-power aerosol lidars and automatic sun/sky/polarized/lunar photometers, which are made available through the ACTRIS data portal. Results of quality assurance procedures applied by the Centre for Aerosol Remote Sensing will be traced into the data products.

ACTRIS Data Centre is responsible for **implementing the approved retrieval algorithms or tools** into the ACTRIS Data Centre operation

The workflow between the ACTRIS NFs, the Centre for Aerosol Remote Sensing and the ACTRIS Data Centre is described in the diagrams below, for each component:

### 8.2.2.1 Aerosol high-power lidar (AHL)

<figure><img src="image_15.png" /></figure>

**Note:** Processing of the high-power aerosol lidar data is done at the ACTRIS DC. Aerosol remote sensing NFs should transfer level 0 data directly to the DC. CARS should transfer the results of QA procedures in machine readable format to the ACTRIS DC.
<figure><img src="image_15.png" /></figure>

**Note:** Aerosol data products retrieved from ALCs which are collocated with cloud radars and microwave radiometers will be used as inputs in the processing chain for cloud remote sensing. This data will be passed to the DC for further calculation of the related ACTRIS variables. Aerosol data products retrieved from the automatic low-power lidars which are not accompanied by cloud radar and microwave radiometer will be processed and managed at CARS until a specialized Unit will be put in place at the DC.

### 8.2.2.2 Automatic sun/sky/polarized/lunar photometer (ASP)

<figure><img src="image_16.png" /></figure>
<figure><img src="image_16.png" /></figure>

**Note:** Aerosol data products retrieved from ALCs which are collocated with cloud radars and microwave radiometers will be used as inputs in the processing chain for cloud remote sensing. This data will be passed to the DC for further calculation of the related ACTRIS variables. Aerosol data products retrieved from the automatic low-power lidars which are not accompanied by cloud radar and microwave radiometer will be processed and managed at CARS until a specialized Unit will be put in place at the DC.

### 8.2.2.2 Automatic sun/sky/polarized/lunar photometer (ASP)

<figure><img src="image_17.png" /></figure>
**Note:** Level 0 data will be received, stored and archived at CARS. Level 1 and current Level 2 are produced at CARS, and corresponding data flow sent to DC. Higher levels production and products will be performed and stored, and archived at ACTRIS DC both for single instrument processing and synergetic processing and products.

**Note:** For synergy between photometer and lidar, easy access to cloud-free QC SCC level 1 is requested. Link to, at least, ground-based co-located in situ (ground and in altitude) scattering and absorption coefficients has to be considered too.

### 8.2.3 Technical obligations in relation with the Centre for Cloud Remote Sensing

There is a close link to the Centre for Cloud Remote Sensing because low-power lidars belong to the minimum required instrumentation of NFs for cloud remote sensing. All quality assurance activities concerning cloud products from ALCs are covered by the TC for cloud remote sensing, but should be strongly supported by CARS. An intensive communication between CARS and the Centre for Cloud Remote Sensing is mandatory to ensure that all recommended SOPs and methods do not reduce the quality of cloud products from automatic low-power lidars at NFs for cloud remote sensing (CLOUDNET sites).

As a feed-back, information from the cloud remote sensing NFs should be used for improving cloud detection in the retrieval algorithm of ASP and AHL (a posteriori).

### 8.2.4 Technical obligations in relation with the ACTRIS users

The Centre for Aerosol Remote Sensing should commit to provide a minimum amount of user services as described in section 4. The provision of services will be made on case-by case situation.

As an important contribution of the Centre for Aerosols Remote Sensing to worldwide networks like AERONET is foreseen that the service, currently free in ACTRIS-2 will remain free for academic and public users, at least.

## 8.3 Evaluation of the activity of the Centre for Aerosol Remote Sensing

Once established and operational, the Centre for Aerosol Remote Sensing will be annually evaluated for its performances, against the following KPIs:

<table><thead><tr><th>Criteria</th><th>Indicator</th><th>Planned value</th><th>Achieved value</th><th>Percentage of achievement<sup>4</sup></th><th>Weight</th></tr></thead><tbody><tr><td></td><td><strong>GENERAL SCORE</strong></td><td></td><td></td><td></td><td></td></tr><tr><td rowspan="3">Usefulness for</td><td><strong>CRITERIA TOTAL SCORE</strong></td><td></td><td></td><td></td><td rowspan="3">40%</td></tr><tr><td>No. of operation support units provided to ACTRIS NFs for quality assurance and quality control</td><td></td><td></td><td></td></tr><tr><td>No. of operation support units provided to ACTRIS NFs for knowledge transfer and training</td><td></td><td></td><td></td></tr></tbody></table>

<footnote n="4">⁴ With regard to the planned and approved values</footnote>
**Note:** Level 0 data will be received, stored and archived at CARS. Level 1 and current Level 2 are produced at CARS, and corresponding data flow sent to DC. Higher levels production and products will be performed and stored, and archived at ACTRIS DC both for single instrument processing and synergetic processing and products.

**Note:** For synergy between photometer and lidar, easy access to cloud-free QC SCC level 1 is requested. Link to, at least, ground-based co-located in situ (ground and in altitude) scattering and absorption coefficients has to be considered too.

### 8.2.3 Technical obligations in relation with the Centre for Cloud Remote Sensing

There is a close link to the Centre for Cloud Remote Sensing because low-power lidars belong to the minimum required instrumentation of NFs for cloud remote sensing. All quality assurance activities concerning cloud products from ALCs are covered by the TC for cloud remote sensing, but should be strongly supported by CARS. An intensive communication between CARS and the Centre for Cloud Remote Sensing is mandatory to ensure that all recommended SOPs and methods do not reduce the quality of cloud products from automatic low-power lidars at NFs for cloud remote sensing (CLOUDNET sites).

As a feed-back, information from the cloud remote sensing NFs should be used for improving cloud detection in the retrieval algorithm of ASP and AHL (a posteriori).

### 8.2.4 Technical obligations in relation with the ACTRIS users

The Centre for Aerosol Remote Sensing should commit to provide a minimum amount of user services as described in section 4. The provision of services will be made on case-by case situation.

As an important contribution of the Centre for Aerosols Remote Sensing to worldwide networks like AERONET is foreseen that the service, currently free in ACTRIS-2 will remain free for academic and public users, at least.

## 8.3 Evaluation of the activity of the Centre for Aerosol Remote Sensing

Once established and operational, the Centre for Aerosol Remote Sensing will be annually evaluated for its performances, against the following KPIs:

<table><thead><tr><th>Criteria</th><th>Indicator</th><th>Planned value</th><th>Achieved value</th><th>Percentage of achievement<sup>4</sup></th><th>Weight</th></tr></thead><tbody><tr><td></td><td><strong>GENERAL SCORE</strong></td><td></td><td></td><td></td><td></td></tr><tr><td rowspan="3">Usefulness for</td><td><strong>CRITERIA TOTAL SCORE</strong></td><td></td><td></td><td></td><td rowspan="3">40%</td></tr><tr><td>No. of operation support units provided to ACTRIS NFs for quality assurance and quality control</td><td></td><td></td><td></td></tr><tr><td>No. of operation support units provided to ACTRIS NFs for knowledge transfer and training</td><td></td><td></td><td></td></tr></tbody></table>

<footnote n="4">⁴ With regard to the planned and approved values</footnote>
Section 4 - Concept of Centre for Aerosol Remote Sensing

<table><tbody><tr><td></td><td>No. of operation support units provided to ACTRIS NFs for Improvement of measurement and data processing methodologies</td><td></td><td></td></tr><tr><td></td><td>Average score of satisfaction received from NFs Including utility, fairness and timeliness of the activities for operation support</td><td></td><td></td></tr><tr><td rowspan="5">Usefulness for ACTRIS users</td><td>CRITERIA TOTAL SCORE</td><td></td><td>20%</td></tr><tr><td>No. of service units provided to ACTRIS users for quality assurance and quality control</td><td></td><td></td></tr><tr><td>No. of service units provided to ACTRIS users for knowledge transfer and training</td><td></td><td></td></tr><tr><td>No. of service units provided to ACTRIS users for improvement of measurement and data processing methodologies</td><td></td><td></td></tr><tr><td>Average score of satisfaction received from ACTRIS users Including utility, fairness and timeliness of the services performed</td><td></td><td></td></tr><tr><td rowspan="4">Impact on science &amp; Integration into ACTRIS</td><td>CRITERIA TOTAL SCORE</td><td></td><td>20%</td></tr><tr><td>No. of new technological products, methods and algorithms developed / improved</td><td></td><td></td></tr><tr><td>No. of peer-review CF-related papers published</td><td></td><td></td></tr><tr><td>No. of CF-related communications at scientific conferences/workshops</td><td></td><td></td></tr><tr><td></td><td>No. of CF-related patents promoted</td><td></td><td></td></tr><tr><td rowspan="5">Integration into ACTRIS</td><td>CRITERIA TOTAL SCORE</td><td></td><td>20%</td></tr><tr><td>No. of participations to ACTRIS committees and boards</td><td></td><td></td></tr><tr><td>No. of activities performed in collaboration with other TCs (joint SOPs, joint workshops, etc.)</td><td></td><td></td></tr><tr><td>Average score of satisfaction received from ACTRIS DC for the contribution to documentation and traceability of data products</td><td></td><td></td></tr><tr><td>Average score of satisfaction received from ACTRIS HO for the quality and readiness of the reports</td><td></td><td></td></tr></tbody></table>
Section 4 - Concept of Centre for Aerosol Remote Sensing

<table><tbody><tr><td></td><td>No. of operation support units provided to ACTRIS NFs for Improvement of measurement and data processing methodologies</td><td></td><td></td></tr><tr><td></td><td>Average score of satisfaction received from NFs Including utility, fairness and timeliness of the activities for operation support</td><td></td><td></td></tr><tr><td rowspan="5">Usefulness for ACTRIS users</td><td>CRITERIA TOTAL SCORE</td><td></td><td>20%</td></tr><tr><td>No. of service units provided to ACTRIS users for quality assurance and quality control</td><td></td><td></td></tr><tr><td>No. of service units provided to ACTRIS users for knowledge transfer and training</td><td></td><td></td></tr><tr><td>No. of service units provided to ACTRIS users for improvement of measurement and data processing methodologies</td><td></td><td></td></tr><tr><td>Average score of satisfaction received from ACTRIS users Including utility, fairness and timeliness of the services performed</td><td></td><td></td></tr><tr><td rowspan="5">Impact on science &amp; Integration into ACTRIS</td><td>CRITERIA TOTAL SCORE</td><td></td><td>20%</td></tr><tr><td>No. of new technological products, methods and algorithms developed / improved</td><td></td><td></td></tr><tr><td>No. of peer-review CF-related papers published</td><td></td><td></td></tr><tr><td>No. of CF-related communications at scientific conferences/workshops</td><td></td><td></td></tr><tr><td>No. of CF-related patents promoted</td><td></td><td></td></tr><tr><td></td><td>CRITERIA TOTAL SCORE</td><td></td><td>20%</td></tr><tr><td></td><td>No. of participations to ACTRIS committees and boards</td><td></td><td></td></tr><tr><td></td><td>No. of activities performed in collaboration with other TCs (joint SOPs, joint workshops, etc.)</td><td></td><td></td></tr><tr><td></td><td>Average score of satisfaction received from ACTRIS DC for the contribution to documentation and traceability of data products</td><td></td><td></td></tr><tr><td></td><td>Average score of satisfaction received from ACTRIS HO for the quality and readiness of the reports</td><td></td><td></td></tr></tbody></table>
List of acronyms

ABL – Aerosol Boundary Layer

AHL – High-power Aerosol Lidar

ALC – Automatic Low-power aerosol Lidar

ASP – Automatic Sun/sky/lunar Photometer

CARS – Centre for Aerosol Remote Sensing

CF – Central Facility

Hol - Handbook of Instruments

NF – National Facility

NRT – Near Real Time

QA – Quality Assurance

QC – Quality Control

SCC – Single Calculus Chain

SOP – Standard Operation Procedure

TC – Topical Centre
List of acronyms

ABL – Aerosol Boundary Layer

AHL – High-power Aerosol Lidar

ALC – Automatic Low-power aerosol Lidar

ASP – Automatic Sun/sky/lunar Photometer

CARS – Centre for Aerosol Remote Sensing

CF – Central Facility

Hol - Handbook of Instruments

NF – National Facility

NRT – Near Real Time

QA – Quality Assurance

QC – Quality Control

SCC – Single Calculus Chain

SOP – Standard Operation Procedure

TC – Topical Centre
Glossary

**ACTRIS data** - are the ACTRIS variables resulting from measurements that fully comply with the standard operating procedures (SOP), measurement recommendations, and quality guidelines established within ACTRIS.

○ **ACTRIS level 0 data:** Raw sensor output, either mV or physical units. Native resolution, metadata necessary for next level.

○ **ACTRIS level 1 data:** Calibrated and quality assured data with minimum level of quality control.

o **ACTRIS level 2 data:** Approved and fully quality controlled ACTRIS data product or geophysical variable.

○ ACTRIS level 3 data: Elaborated ACTRIS data products derived by post-processing of ACTRIS Level 0 - 1 -2 data, and data from other sources. The data can be gridded or not.

o **ACTRIS syntheses product (Proper name to be defined later):** Data product from e.g. research activities, not under direct ACTRIS responsibility, but ACTRIS offer repository and access.

**ACTRIS Data Centre (DC)** - the Central Facility responsible for ACTRIS data curation, preservation, and distribution of data, value-added products and tools, and hosting the ACTRIS data portal.

**ACTRIS data originator** - entity operating instruments at a National Facility or Topical Centre, resulting in ACTRIS data and delivering ACTRIS data to the Data Centre.

**ACTRIS data provider** - the Data Centre offering the ACTRIS data and value-added data products and tools to users.

**ACTRIS digital tools and services** - tailored codes and software for processing and visualization of ACTRIS data, production of ACTRIS data products, and for data analysis and research.

**ACTRIS exploratory platform** - National Facility (simulation chambers, laboratories, or mobile facilities) operating on campaign basis and delivering dedicated data to the Data Centre.

**ACTRIS General Assembly (GA)** - a council of ministry- and funding organization representatives of ACTRIS members after ACTRIS legal entity has been established, superior decision-making body of ACTRIS.

**ACTRIS Head Office (HO)** - a Central Facility coordinating and representing ACTRIS, and holding the statutory seat.

**ACTRIS label** - earmarks a data set or a measurement site as ACTRIS data or ACTRIS National Facility.

**ACTRIS observational platform** – ACTRIS National Facility performing long-term, regular observations and delivering standardized data to the Data Centre.

**ACTRIS Topical Centres (TCs)** – a Central Facility offering services and operation support for QA/QC of measurements and data (including training, calibration, QA/QC tools, and development of standard operation and evaluation procedures)

**ACTRIS variables** - the measured atmospheric variables as described in the [ACTRIS Data Management Plan<fnref n="5" />](#).

<footnote n="5">⁵The [ACTRIS data management plan](#) and list of variables were approved by ACTRIS-2 scientific steering committee, October 2015. These documents are expected to be refined during ACTRIS-PPP (WP5).</footnote>
Glossary

**ACTRIS data** - are the ACTRIS variables resulting from measurements that fully comply with the standard operating procedures (SOP), measurement recommendations, and quality guidelines established within ACTRIS.

○ **ACTRIS level 0 data:** Raw sensor output, either mV or physical units. Native resolution, metadata necessary for next level.

○ ACTRIS level 1 data: Calibrated and quality assured data with minimum level of quality control.

o ACTRIS level 2 data: Approved and fully quality controlled ACTRIS data product or geophysical variable.

○ ACTRIS level 3 data: Elaborated ACTRIS data products derived by post-processing of ACTRIS Level 0 - 1 -2 data, and data from other sources. The data can be gridded or not.

o ACTRIS **syntheses product** (*Proper name to be defined later*): Data product from e.g. research activities, not under direct ACTRIS responsibility, but ACTRIS offer repository and access.

ACTRIS Data Centre (DC) - the Central Facility responsible for ACTRIS data curation, preservation, and distribution of data, value-added products and tools, and hosting the ACTRIS data portal.

**ACTRIS data originator** - entity operating instruments at a National Facility or Topical Centre, resulting in ACTRIS data and delivering ACTRIS data to the Data Centre.

**ACTRIS data provider** - the Data Centre offering the ACTRIS data and value-added data products and tools to users.

**ACTRIS digital tools and services** - tailored codes and software for processing and visualization of ACTRIS data, production of ACTRIS data products, and for data analysis and research.

**ACTRIS exploratory platform** - National Facility (simulation chambers, laboratories, or mobile facilities) operating on campaign basis and delivering dedicated data to the Data Centre.

**ACTRIS General Assembly (GA)** - a council of ministry- and funding organization representatives of ACTRIS members after ACTRIS legal entity has been established, superior decision-making body of ACTRIS.

**ACTRIS Head Office (HO)** - a Central Facility coordinating and representing ACTRIS, and holding the statutory seat.

**ACTRIS label** - earmarks a data set or a measurement site as ACTRIS data or ACTRIS National Facility.

**ACTRIS observational platform** – ACTRIS National Facility performing long-term, regular observations and delivering standardized data to the Data Centre.

**ACTRIS Topical Centres (TCs)** – a Central Facility offering services and operation support for QA/QC of measurements and data (including training, calibration, QA/QC tools, and development of standard operation and evaluation procedures)

**ACTRIS variables** - the measured atmospheric variables as described in the [ACTRIS Data Management Plan<fnref n="5" />](#).

<footnote n="5">⁵The [ACTRIS data management plan](#) and list of variables were approved by ACTRIS-2 scientific steering committee, October 2015. These documents are expected to be refined during ACTRIS-PPP (WP5).</footnote>
**Central Facility (CF)** - a European level ACTRIS component that offers ACTRIS data or other ACTRIS services to users as well as operation support to ACTRIS National Facilities.

**Central Facility Unit** – part of a Central Facility located at, and operated by a research performing organization (RPO) or by ACTRIS ERIC.

**CF Director** – the person responsible for the coordination and representation of a Central Facility.

**CF Unit Head** – the person responsible for the coordination and representation of a Central Facility unit.

**CF Management Board** – consists of the CF Unit Heads and the CF Director; this board manages the Central Facility.

**Data curation** - the activity that stores, manages and ensures access to all persistent data sets produced within the infrastructure.

**Data traceability** - an unbroken chain of uniquely identified process steps leading from raw data to any kind of processed data, where identification of process steps follows the data.

**In situ measurements** - measured or sampled air and instrument are at the same location and in physical contact. In the context of ACTRIS, in situ measurements of aerosol, cloud, and reactive-trace-gas properties are performed at observational sites near the Earth surface, on mobile surface-based or airborne platforms, and in atmospheric simulation chambers and laboratories.

**Interim ACTRIS Council** - a council of ministry- and funding organization representatives of ACTRIS members before ACTRIS legal entity has been established (during the ACTRIS Preparation and Transition Phase), superior decision-making body of ACTRIS.

**Measurement traceability** - an unbroken chain of comparisons relating an instrument's measurements to a known standard, in the ideal case SI units.

**National Facility (NF)** - an observational or exploratory platform providing data and/or physical access to the platform within ACTRIS.

**Quality assurance and control:** Quality assurance is process oriented and focuses on defect prevention; quality control is product oriented and focuses on defect identification:

* **Quality Assurance (QA):** The process or set of processes used to ensure the quality of a product (e.g. data series, instrument, sample, measured value of a variable, etc.),

* **Quality Control (QC):** The process and activities of ensuring products and services meet the expectations.

**Remote sensing** - measured air and instrument are not at the same location and not in physical contact. In the context of ACTRIS, active and passive atmospheric remote-sensing techniques for the observation of aerosols, clouds, and trace gases are applied at observational sites and on mobile surface-based or airborne platforms.

**RI committee** – consists of up to two representatives from each Central Facility and [three] representatives from the National Facilities Assembly; the RI committee supports the (Interim) Director or Board of Directors in operating the RI.

**Service and Access Management Unit (SAMU)** - a part of ACTRIS Head Office facilitating the access to ACTRIS services.

**User** - a person, a team, or an institution making use of ACTRIS data or other ACTRIS services, including access to ACTRIS facilities.
**Central Facility (CF)** - a European level ACTRIS component that offers ACTRIS data or other ACTRIS services to users as well as operation support to ACTRIS National Facilities.

**Central Facility Unit** – part of a Central Facility located at, and operated by a research performing organization (RPO) or by ACTRIS ERIC.

**CF Director** – the person responsible for the coordination and representation of a Central Facility.

**CF Unit Head** – the person responsible for the coordination and representation of a Central Facility unit.

**CF Management Board** – consists of the CF Unit Heads and the CF Director; this board manages the Central Facility.

**Data curation** - the activity that stores, manages and ensures access to all persistent data sets produced within the infrastructure.

**Data traceability** - an unbroken chain of uniquely identified process steps leading from raw data to any kind of processed data, where identification of process steps follows the data.

**In situ measurements** - measured or sampled air and instrument are at the same location and in physical contact. In the context of ACTRIS, in situ measurements of aerosol, cloud, and reactive-trace-gas properties are performed at observational sites near the Earth surface, on mobile surface-based or airborne platforms, and in atmospheric simulation chambers and laboratories.

**Interim ACTRIS Council** - a council of ministry- and funding organization representatives of ACTRIS members before ACTRIS legal entity has been established (during the ACTRIS Preparation and Transition Phase), superior decision-making body of ACTRIS.

**Measurement traceability** - an unbroken chain of comparisons relating an instrument's measurements to a known standard, in the ideal case SI units.

**National Facility (NF)** - an observational or exploratory platform providing data and/or physical access to the platform within ACTRIS.

**Quality assurance and control:** Quality assurance is process oriented and focuses on defect prevention; quality control is product oriented and focuses on defect identification:

* **Quality Assurance (QA):** The process or set of processes used to ensure the quality of a product (e.g. data series, instrument, sample, measured value of a variable, etc.),

* **Quality Control (QC):** The process and activities of ensuring products and services meet the expectations.

**Remote sensing** - measured air and instrument are not at the same location and not in physical contact. In the context of ACTRIS, active and passive atmospheric remote-sensing techniques for the observation of aerosols, clouds, and trace gases are applied at observational sites and on mobile surface-based or airborne platforms.

**RI committee** – consists of up to two representatives from each Central Facility and [three] representatives from the National Facilities Assembly; the RI committee supports the (Interim) Director or Board of Directors in operating the RI.

**Service and Access Management Unit (SAMU)** - a part of ACTRIS Head Office facilitating the access to ACTRIS services.

**User** - a person, a team, or an institution making use of ACTRIS data or other ACTRIS services, including access to ACTRIS facilities.
Reference documents

ACTRIS-ESFRI proposal

ACTRIS-PPP proposal

ACTRIS Stakeholders Handbook 2017

ACTRIS Science Case document

ACTRIS Data Management Plan, approved by ACTRIS-2 SSC 23 October 2015

Baseline document for the Concepts of ACTRIS Central Facilities

Technical concepts and requirements for ACTRIS Observational Platforms

Technical concepts and requirements for ACTRIS Exploratory Platforms

ISO 10012:2003: Measurement management systems — Requirements for measurement processes and measuring equipment

ISO 9000:2015: Quality management systems—Fundamentals and vocabulary

Barreto, A., Cuevas, E., Damiri, B., Guirado, C., Berkoff, T., Berjón, A. J., Hernández, Y., Almansa, F., and Gil, M.: A new method for nocturnal aerosol measurements with a lu-nar photometer prototype, Atmos. Meas. Tech., 6, 585–598, https://doi.org/10.5194/amt-6-585-2013, 2013a.

Barreto, A., Cuevas, E., Damiri, B., Romero, P. M., and Almansa, F.: Column water vapour determination in night period with a lunar photometer prototype, Atmos. Meas. Tech., 6, 2159–2167, https://doi.org/10.5194/amt-6-2159-2013, 2013b.

Barreto, Á., Cuevas, E., Granados-Muñoz, M.-J., Alados-Arboledas, L., Romero, P. M., Gröbner, J., Kouremeti, N., Almansa, A. F., Stone, T., Toledano, C., Román, R., Sorokin, M., Holben, B., Canini, M., and Yela, M.: The new sun-sky-lunar Cimel CE318-T multiband photometer – a comprehensive performance evaluation, Atmos. Meas. Tech., 9, 631–654, https://doi.org/10.5194/amt-9-631-2016, 2016.

Barreto, R., Román, E., Cuevas, Alberto J., Berjón A., Fernando Almansa, Carlos Toledano, Ramiro González, Yballa Hernández, Luc Blarel, Philippe Goloub, Carmen Guirado, and Margarita Yela, Assessment of nocturnal aerosol optical depth from lunar photometry at the Izaña high mountain observatory, Atmos. Meas. Tech., 10, 3007–3019, 2017, https://doi.org/10.5194/amt-10-3007-2017

Belegante, L., Bravo-Aranda, J. A., Freudenthaler, V., Nicolae, D., Nemuc, A., Alados-Arboledas, L., Amodeo, A., Pappalardo, G., D'Amico, G., Engelmann, R., Baars, H., Wandinger, U., Papayannis, A., Kokkalis, P., and Pereira, S. N.: Experimental techniques for the calibration of lidar depolarization channels in EARLINET, Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2017-141, in review, 2017.

Bravo-Aranda, J. A., Belegante, L., Freudenthaler, V., Alados-Arboledas, L., Nicolae, D., Granados-Muñoz, M. J., Guerrero-Rascado, J. L., Amodeo, A., D'Amico, G., Engelmann, R., Pappalardo, G., Kokkalis, P., Mamouri, R., Papayannis, A., Navas-Guzmán, F., Olmo, F. J., Wandinger, U., Amato, F., and Haeffelin,
Reference documents

ACTRIS-ESFRI proposal

ACTRIS-PPP proposal

ACTRIS Stakeholders Handbook 2017

ACTRIS Science Case document

ACTRIS Data Management Plan, approved by ACTRIS-2 SSC 23 October 2015

Baseline document for the Concepts of ACTRIS Central Facilities

Technical concepts and requirements for ACTRIS Observational Platforms

Technical concepts and requirements for ACTRIS Exploratory Platforms

ISO 10012:2003: Measurement management systems — Requirements for measurement processes and measuring equipment

ISO 9000:2015: Quality management systems—Fundamentals and vocabulary

Barreto, A., Cuevas, E., Damiri, B., Guirado, C., Berkoff, T., Berjón, A. J., Hernández, Y., Almansa, F., and Gil, M.: A new method for nocturnal aerosol measurements with a lu-nar photometer prototype, Atmos. Meas. Tech., 6, 585–598, https://doi.org/10.5194/amt-6-585-2013, 2013a.

Barreto, A., Cuevas, E., Damiri, B., Romero, P. M., and Almansa, F.: Column water vapour determination in night period with a lunar photometer prototype, Atmos. Meas. Tech., 6, 2159–2167, https://doi.org/10.5194/amt-6-2159-2013, 2013b.

Barreto, Á., Cuevas, E., Granados-Muñoz, M.-J., Alados-Arboledas, L., Romero, P. M., Gröbner, J., Kouremeti, N., Almansa, A. F., Stone, T., Toledano, C., Román, R., Sorokin, M., Holben, B., Canini, M., and Yela, M.: The new sun-sky-lunar Cimel CE318-T multiband photometer – a comprehensive performance evaluation, Atmos. Meas. Tech., 9, 631–654, https://doi.org/10.5194/amt-9-631-2016, 2016.

Barreto, R., Román, E., Cuevas, Alberto J., Berjón, A., Fernando Almansa, Carlos Toledano, Ramiro González, Yballa Hernández, Luc Blarel, Philippe Goloub, Carmen Guirado, and Margarita Yela, Assessment of nocturnal aerosol optical depth from lunar photometry at the Izaña high mountain observatory, Atmos. Meas. Tech., 10, 3007–3019, 2017, https://doi.org/10.5194/amt-10-3007-2017

Belegante, L., Bravo-Aranda, J. A., Freudenthaler, V., Nicolae, D., Nemuc, A., Alados-Arboledas, L., Amodeo, A., Pappalardo, G., D'Amico, G., Engelmann, R., Baars, H., Wandinger, U., Papayannis, A., Kokkalis, P., and Pereira, S. N.: Experimental techniques for the calibration of lidar depolarization channels in EARLINET, Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2017-141, in review, 2017.

Bravo-Aranda, J. A., Belegante, L., Freudenthaler, V., Alados-Arboledas, L., Nicolae, D., Granados-Muñoz, M. J., Guerrero-Rascado, J. L., Amodeo, A., D'Amico, G., Engelmann, R., Pappalardo, G., Kokkalis, P., Mamouri, R., Papayannis, A., Navas-Guzmán, F., Olmo, F. J., Wandinger, U., Amato, F., and Haeffelin,
M.: Assessment of lidar depolarization uncertainty by means of a polarimetric lidar simulator, Atmos. Meas. Tech., 9, 4935-4953, https://doi.org/10.5194/amt-9-4935-2016, 2016.

Dubovik, O., Herman, M., Holdak, A., Lapyonok, T., Tanré, D., Deuzé, J. L., Ducos, F., Sinyuk, A. and Lopatin, A.: Statistically optimized inversion algorithm for enhanced retrieval of aerosol properties from spectral multi-angle polarimetric satellite observations, Atmos. Meas. Tech., 4(5), 975–1018, doi:10.5194/amt-4-975-2011, 2011.

Dubovik, O., L. Labonnote, P. Litvinov, F. Parol, and M.I. Mishchenko, 2014: Electromagnetic and Light Scattering by Nonspherical Particles XIV. J. Quant. Spectrosc. Radiat. Transfer, 146, 1-3, doi:10.1016/j.jqsrt.2014.04.006

Dubovik, O., Smirnov, A., Holben, B.N., King, M.D., Kaufman, Y.J., Eck, T.F., Slutsker, I., 2000. Accuracy assessments of aerosol optical properties retrieved from Aerosol Robotic Network (AERONET) Sun and sky radiance measurements. Journal of Geophysical Research: Atmospheres 105, 9791–9806.

Freudenthaler, V., About the effects of polarising optics on lidar signals and the Δ90-calibration, Atmos. Meas. Tech., 2016, 9, 4181-4255

Freudenthaler, V., et al., EARLINET lidar quality assurance tools, submitted to Atmos. Meas. Tech, amt-2017-395

Freudenthaler, Volker; Seefeldner, Meinhard; Groß, Silke & Wandinger, Ulla, Accuracy of Linear Depolarisation Ratios in Clean Air Ranges Measured with POLIS-6 at 355 and 532 NM EPJ Web of Conferences, 2016, 119, 25013

Holben, B. N., T. F. Eck, I. Slutsker, A. Smirnov, A. Sinyuk, J. Schafer, D. Giles, O. Dubovik, 2006: Aeronet's Version 2.0 quality assurance criteria, Proc. SPIE 6408, Remote Sensing of the Atmosphere and Clouds, 64080Q, doi:10.1117/12.706524.

Holben, B. N., Tanré, D., Smirnov, A., Eck, T. F., Slutsker, I., Abuhassan, N., Newcomb, W. W., Schafer, J. S., Chatenet, B., Lavenu, F., Kaufman, Y. J., Castle, J. V., Setzer, A., Markham, B., Clark, D., Frouin, R., Halthore, R., Karneli, A., O'Neill, N. T., Pietras, C., Pinker, R. T., Voss, K. and Zibordi, G.: An emerging ground-based aerosol climatology: Aerosol optical depth from AERONET, Journal of Geophysical Research: Atmospheres, 106(D11), 12067–12097, doi:10.1029/2001JD900014, 2001.

Li Z, P. Goloub, L. Blarel, B. Yang, K. Li, T. Podvin, D. Li, Y. Xie, X. Chen, X. Gu, X. Zheng, J. Li, M. Catalfamo, Method to intercalibrate sunphotometer constants using an integrating sphere as a light source in the laboratory, 2013, APPLIED OPTICS / Vol. 52, No. 11 / 10 April 2013

Li, L., Maher, K., Navarre-Sitchler, A., Druhan, J., Meile, C., Lawrence, C., Moore, J., Perdrial, J., Sullivan, P., Thompson, A., Jin, L., Bolton, E. W., Brantley, S. L., Dietrich, W. E., Mayer, K. U., Steefel, C. I., Valocchi, A., Zachara, J., Kocar, B., Mcintosh, J., Tutolo, B. M., Kumar, M., Sonnenthal, E., Bao, C. and Beisman, J.: Expanding the role of reactive transport models in critical zone processes, Earth-Science Reviews, 165, 280–301, doi:10.1016/j.earscirev.2016.09.001, 2017.

Li, X., Zhu, J., Xiao, Y. and Wang, R.: A Model-Based Observation-Thinning Scheme for the Assimilation of High-Resolution SST in the Shelf and Coastal Seas around China, Journal of Atmospheric and Oceanic Technology, 27(6), 1044–1058, doi:10.1175/2010JTECHO709.1, 2010.

Li, Z., Lau, W. K.-M., Ramanathan, V., Wu, G., Ding, Y., Manoj, M. G., Liu, J., Qian, Y., Li, J., Zhou, T., Fan, J., Rosenfeld, D., Ming, Y., Wang, Y., Huang, J., Wang, B., Xu, X., Lee, S.-S., Cribb, M., Zhang, F., Yang, X., Zhao, C., Takemura, T., Wang, K., Xia, X., Yin, Y., Zhang, H., Guo, J., Zhai, P. M., Sugimoto, N.,
M.: Assessment of lidar depolarization uncertainty by means of a polarimetric lidar simulator, Atmos. Meas. Tech., 9, 4935-4953, https://doi.org/10.5194/amt-9-4935-2016, 2016.

Dubovik, O., Herman, M., Holdak, A., Lapyonok, T., Tanré, D., Deuzé, J. L., Ducos, F., Sinyuk, A. and Lopatin, A.: Statistically optimized inversion algorithm for enhanced retrieval of aerosol properties from spectral multi-angle polarimetric satellite observations, Atmos. Meas. Tech., 4(5), 975–1018, doi:10.5194/amt-4-975-2011, 2011.

Dubovik, O., L. Labonnote, P. Litvinov, F. Parol, and M.I. Mishchenko, 2014: Electromagnetic and Light Scattering by Nonspherical Particles XIV. J. Quant. Spectrosc. Radiat. Transfer, 146, 1-3, doi:10.1016/j.jqsrt.2014.04.006

Dubovik, O., Smirnov, A., Holben, B.N., King, M.D., Kaufman, Y.J., Eck, T.F., Slutsker, I., 2000. Accuracy assessments of aerosol optical properties retrieved from Aerosol Robotic Network (AERONET) Sun and sky radiance measurements. Journal of Geophysical Research: Atmospheres 105, 9791–9806.

Freudenthaler, V., About the effects of polarising optics on lidar signals and the Δ90-calibration, Atmos. Meas. Tech., 2016, 9, 4181-4255

Freudenthaler, V., et al., EARLINET lidar quality assurance tools, submitted to Atmos. Meas. Tech, amt-2017-395

Freudenthaler, Volker; Seefeldner, Meinhard; Groß, Silke & Wandinger, Ulla, Accuracy of Linear Depolarisation Ratios in Clean Air Ranges Measured with POLIS-6 at 355 and 532 NM EPJ Web of Conferences, 2016, 119, 25013

Holben, B. N., T. F. Eck, I. Slutsker, A. Smirnov, A. Sinyuk, J. Schafer, D. Giles, O. Dubovik, 2006: Aeronet's Version 2.0 quality assurance criteria, Proc. SPIE 6408, Remote Sensing of the Atmosphere and Clouds, 64080Q, doi:10.1117/12.706524.

Holben, B. N., Tanré, D., Smirnov, A., Eck, T. F., Slutsker, I., Abuhassan, N., Newcomb, W. W., Schafer, J. S., Chatenet, B., Lavenu, F., Kaufman, Y. J., Castle, J. V., Setzer, A., Markham, B., Clark, D., Frouin, R., Halthore, R., Karneli, A., O'Neill, N. T., Pietras, C., Pinker, R. T., Voss, K. and Zibordi, G.: An emerging ground-based aerosol climatology: Aerosol optical depth from AERONET, Journal of Geophysical Research: Atmospheres, 106(D11), 12067–12097, doi:10.1029/2001JD900014, 2001.

Li Z, P. Goloub, L. Blarel, B. Yang, K. Li, T. Podvin, D. Li, Y. Xie, X. Chen, X. Gu, X. Zheng, J. Li, M. Catalfamo, Method to intercalibrate sunphotometer constants using an integrating sphere as a light source in the laboratory, 2013, APPLIED OPTICS / Vol. 52, No. 11 / 10 April 2013

Li, L., Maher, K., Navarre-Sitchler, A., Druhan, J., Meile, C., Lawrence, C., Moore, J., Perdrial, J., Sullivan, P., Thompson, A., Jin, L., Bolton, E. W., Brantley, S. L., Dietrich, W. E., Mayer, K. U., Steefel, C. I., Valocchi, A., Zachara, J., Kocar, B., Mcintosh, J., Tutolo, B. M., Kumar, M., Sonnenthal, E., Bao, C. and Beisman, J.: Expanding the role of reactive transport models in critical zone processes, Earth-Science Reviews, 165, 280–301, doi:10.1016/j.earscirev.2016.09.001, 2017.

Li, X., Zhu, J., Xiao, Y. and Wang, R.: A Model-Based Observation-Thinning Scheme for the Assimilation of High-Resolution SST in the Shelf and Coastal Seas around China, Journal of Atmospheric and Oceanic Technology, 27(6), 1044–1058, doi:10.1175/2010JTECHO709.1, 2010.

Li, Z., Lau, W. K.-M., Ramanathan, V., Wu, G., Ding, Y., Manoj, M. G., Liu, J., Qian, Y., Li, J., Zhou, T., Fan, J., Rosenfeld, D., Ming, Y., Wang, Y., Huang, J., Wang, B., Xu, X., Lee, S.-S., Cribb, M., Zhang, F., Yang, X., Zhao, C., Takemura, T., Wang, K., Xia, X., Yin, Y., Zhang, H., Guo, J., Zhai, P. M., Sugimoto, N.,
Babu, S. S. and Brasseur, G. P.: Aerosol and monsoon climate interactions over Asia, Rev. Geophys., 54(4), 2015RG000500, doi:10.1002/2015RG000500, 2016.

Lopatin, A., Dubovik, O., Chaikovsky, A., Goloub, P., Lapyonok, T., Tanré, D. and Litvinov, P.: Enhancement of aerosol characterization using synergy of lidar and sun-photometer coincident observations: the GARRLiC algorithm, Atmos. Meas. Tech., 6(8), 2065–2088, doi:10.5194/amt-6-2065-2013, 2013.

Madonna, F., Amato, F., Vande Hey, J., Pappalardo, G., 2015. Ceilometer aerosol profiling versus Raman lidar in the frame of the INTERACT campaign of ACTRIS. Atmos. Meas. Tech. 8, 2207–2223. https://doi.org/10.5194/amt-8-2207-2015

María Beatriz Barreto, Salvador Lo Mónaco, Rut Díaz, Eduardo Barreto-Pittol, Liliana López, Maria do Carmo Ruaro Peralba, Soil organic carbon of mangrove forests (Rhizophora and Avicennia) of the Venezuelan Caribbean coast, In Organic Geochemistry, Volume 100, 2016, Pages 51-61, ISSN 0146-6380, https://doi.org/10.1016/j.orggeochem.2016.08.002.

Mattis, I., Begbie, R., Boyouk, N., Bravo-Aranda, J.A., Brettle, M., Cermak, J., Drouin, M.-A., Geiß, A., Görsdorf, U., Haefele, A., Haeffelin, M., Hervo, M., Komínková, K., Leinweber, R., Müller, G., Münkel, C., Pattantyús-Ábrahám, M., Pönitz, K., Wagner, F., Wiegner, M., 2016. The ceilometer inter-comparison campaign CeiLinEx2015. Presented at the EGU General Assembly Conference Abstracts, pp. EPSC2016-9687.

Smirnov, A., Holben, B., Eck, T., Dubovik, O. and Slutsker, I.: Cloud-Screening and Quality Control Algorithms for the AERONET Database, 2000.

Wandinger, U., Freudenthaler, V., Baars, H., Amodeo, A., Engelmann, R., Mattis, I., Groß, S., Pappalardo, G., Giunta, A., D&aposos;Amico, G., Chaikovsky, A., Osipenko, F., Slesar, A., Nicolae, D., Belegante, L., Talianu, C., Serikov, I., Linné, H., Jansen, F., Apituley, A., Wilson, K.M., de Graaf, M., Trickl, T., Giehl, H., Adam, M., Comerón, A., Muñoz-Porcar, C., Rocadenbosch, F., Sicard, M., Tomás, S., Lange, D., Kumar, D., Pujadas, M., Molero, F., Fernández, A.J., Alados-Arboledas, L., Bravo-Aranda, J.A., Navas-Guzmán, F., Guerrero-Rascado, J.L., Granados-Muñoz, M.J., Preißler, J., Wagner, F., Gausa, M., Grigorov, I., Stoyanov, D., Iarlori, M., Rizi, V., Spinelli, N., Boselli, A., Wang, X., Lo Feudo, T., Perrone, M.R., De Tomasi, F., Burlizzi, P., 2016. EARLINET instrument intercomparison campaigns: overview on strategy and results. Atmospheric Measurement Techniques 9, 1001–1023. https://doi.org/10.5194/amt-9-1001-2016

Wiegner, M., Madonna, F., Binietoglou, I., Forkel, R., Gasteiger, J., Geiß, A., Pappalardo, G., Schäfer, K., and Thomas, W., 2014. What is the benefit of ceilometers for aerosol remote sensing? An answer from EARLINET, Atmos. Meas. Tech., 7, 1979-1997, doi:10.5194/amt-7-1979-2014, 2014.
Babu, S. S. and Brasseur, G. P.: Aerosol and monsoon climate interactions over Asia, Rev. Geophys., 54(4), 2015RG000500, doi:10.1002/2015RG000500, 2016.

Lopatin, A., Dubovik, O., Chaikovsky, A., Goloub, P., Lapyonok, T., Tanré, D. and Litvinov, P.: Enhancement of aerosol characterization using synergy of lidar and sun-photometer coincident observations: the GARRLiC algorithm, Atmos. Meas. Tech., 6(8), 2065–2088, doi:10.5194/amt-6-2065-2013, 2013.

Madonna, F., Amato, F., Vande Hey, J., Pappalardo, G., 2015. Ceilometer aerosol profiling versus Raman lidar in the frame of the INTERACT campaign of ACTRIS. Atmos. Meas. Tech. 8, 2207–2223. https://doi.org/10.5194/amt-8-2207-2015

María Beatriz Barreto, Salvador Lo Mónaco, Rut Díaz, Eduardo Barreto-Pittol, Liliana López, Maria do Carmo Ruaro Peralba, Soil organic carbon of mangrove forests (Rhizophora and Avicennia) of the Venezuelan Caribbean coast, In Organic Geochemistry, Volume 100, 2016, Pages 51-61, ISSN 0146-6380, https://doi.org/10.1016/j.orggeochem.2016.08.002.

Mattis, I., Begbie, R., Boyouk, N., Bravo-Aranda, J.A., Brettle, M., Cermak, J., Drouin, M.-A., Geiß, A., Görsdorf, U., Haefele, A., Haeffelin, M., Hervo, M., Komínková, K., Leinweber, R., Müller, G., Münkel, C., Pattantyús-Ábrahám, M., Pönitz, K., Wagner, F., Wiegner, M., 2016. The ceilometer inter-comparison campaign CeiLinEx2015. Presented at the EGU General Assembly Conference Abstracts, pp. EPSC2016-9687.

Smirnov, A., Holben, B., Eck, T., Dubovik, O. and Slutsker, I.: Cloud-Screening and Quality Control Algorithms for the AERONET Database, 2000.

Wandinger, U., Freudenthaler, V., Baars, H., Amodeo, A., Engelmann, R., Mattis, I., Groß, S., Pappalardo, G., Giunta, A., D&aposos;Amico, G., Chaikovsky, A., Osipenko, F., Slesar, A., Nicolae, D., Belegante, L., Talianu, C., Serikov, I., Linné, H., Jansen, F., Apituley, A., Wilson, K.M., de Graaf, M., Trickl, T., Giehl, H., Adam, M., Comerón, A., Muñoz-Porcar, C., Rocadenbosch, F., Sicard, M., Tomás, S., Lange, D., Kumar, D., Pujadas, M., Molero, F., Fernández, A.J., Alados-Arboledas, L., Bravo-Aranda, J.A., Navas-Guzmán, F., Guerrero-Rascado, J.L., Granados-Muñoz, M.J., Preißler, J., Wagner, F., Gausa, M., Grigorov, I., Stoyanov, D., Iarlori, M., Rizi, V., Spinelli, N., Boselli, A., Wang, X., Lo Feudo, T., Perrone, M.R., De Tomasi, F., Burlizzi, P., 2016. EARLINET instrument intercomparison campaigns: overview on strategy and results. Atmospheric Measurement Techniques 9, 1001–1023. https://doi.org/10.5194/amt-9-1001-2016

Wiegner, M., Madonna, F., Binietoglou, I., Forkel, R., Gasteiger, J., Geiß, A., Pappalardo, G., Schäfer, K., and Thomas, W., 2014. What is the benefit of ceilometers for aerosol remote sensing? An answer from EARLINET, Atmos. Meas. Tech., 7, 1979-1997, doi:10.5194/amt-7-1979-2014, 2014.
# Annex: Provision of the operation support

## Scheduled support

Some of the activities performed by CARS as operation support will be scheduled and, therefore, mandatory for the aerosol remote sensing NFs to participate. The schedule will be announced on the CARS and ACTRIS websites, and communicated with the PIs. A web tool should be developed as part of the CARS website to allow easy and fast registration to the scheduled activities.

<table><thead><tr><th>Technique</th><th>Type of support</th><th>Specific support</th><th>Frequency</th><th>Comments</th></tr></thead><tbody><tr><td rowspan="5">Aerosol high-power lidar (AHL)</td><td>Provision of instrument-specific calibration</td><td>Comparison with fixed reference at calibration site</td><td>Once each 5 years and after each major upgrade</td><td>If the lidar system can be moved to the fixed reference</td></tr><tr><td>Site performance audits with reference samples or mobile systems</td><td>Direct comparison with a mobile reference lidar</td><td>Once each 5 years and after each major upgrade</td><td>If the lidar system cannot be moved to the fixed reference</td></tr><tr><td>Organization of regular exercises to assess the performances of the NFs, including instrument performance workshops</td><td>Expert analysis of the quality assurance tests</td><td>Once per year</td><td>And each time is necessary (instrument low performance)</td></tr><tr><td>Contribution to documentation and traceability of level 0 to level 3 data products</td><td>Reports to ACTRIS DC</td><td>Once per year</td><td>Linked to the expert analysis of the quality assurance tests</td></tr><tr><td>Training of operators and scientists</td><td>Regular training sessions on pre-defined subjects (implementation of SOPs, implementation of the in-house check-up tools, implementation of the data evaluation procedures and plausibility tests, etc.)<br/>Regular WebEx sessions</td><td>Twice per year<br/>Quarterly</td><td></td></tr></tbody></table>

<table><thead><tr><th>Technique</th><th>Type of support</th><th>Specific support</th><th>Frequency</th><th>Comments</th></tr></thead><tbody><tr><td>Automatic low-power lidar / ceilometer (ALC)</td><td>Organization of regular exercises to assess the performances of the NFs, including instrument</td><td>Expert analysis of the quality assurance tests</td><td>Once per year</td><td>And each time is necessary (instrument low performance)</td></tr></tbody></table>
# Annex: Provision of the operation support

## Scheduled support

Some of the activities performed by CARS as operation support will be scheduled and, therefore, mandatory for the aerosol remote sensing NFs to participate. The schedule will be announced on the CARS and ACTRIS websites, and communicated with the PIs. A web tool should be developed as part of the CARS website to allow easy and fast registration to the scheduled activities.

<table><thead><tr><th>Technique</th><th>Type of support</th><th>Specific support</th><th>Frequency</th><th>Comments</th></tr></thead><tbody><tr><td rowspan="5">Aerosol high-power lidar (AHL)</td><td>Provision of instrument-specific calibration</td><td>Comparison with fixed reference at calibration site</td><td>Once each 5 years and after each major upgrade</td><td>If the lidar system can be moved to the fixed reference</td></tr><tr><td>Site performance audits with reference samples or mobile systems</td><td>Direct comparison with a mobile reference lidar</td><td>Once each 5 years and after each major upgrade</td><td>If the lidar system cannot be moved to the fixed reference</td></tr><tr><td>Organization of regular exercises to assess the performances of the NFs, including instrument performance workshops</td><td>Expert analysis of the quality assurance tests</td><td>Once per year</td><td>And each time is necessary (instrument low performance)</td></tr><tr><td>Contribution to documentation and traceability of level 0 to level 3 data products</td><td>Reports to ACTRIS DC</td><td>Once per year</td><td>Linked to the expert analysis of the quality assurance tests</td></tr><tr><td>Training of operators and scientists</td><td>Regular training sessions on pre-defined subjects (implementation of SOPs, implementation of the in-house check-up tools, implementation of the data evaluation procedures and plausibility tests, etc.)<br/>Regular WebEx sessions</td><td>Twice per year<br/>Quarterly</td><td></td></tr></tbody></table>

<table><thead><tr><th>Technique</th><th>Type of support</th><th>Specific support</th><th>Frequency</th><th>Comments</th></tr></thead><tbody><tr><td>Automatic low-power lidar / ceilometer (ALC)</td><td>Organization of regular exercises to assess the performances of the NFs, including instrument</td><td>Expert analysis of the quality assurance tests</td><td>Once per year</td><td>And each time is necessary (instrument low performance)</td></tr></tbody></table>
Section 4 - Concept of Centre for Aerosol Remote Sensing

<table><thead><tr><td>Technique</td><td>Type of support</td><td>Specific support</td><td>Frequency</td><td>Comments</td></tr></thead><tbody><tr><td></td><td>performance workshops</td><td></td><td></td><td></td></tr><tr><td></td><td>Training of operators and scientists</td><td>Regular training sessions on pre-defined subjects</td><td>Once per year</td><td></td></tr></tbody></table>

<table><thead><tr><td>Technique</td><td>Type of support</td><td>Specific support</td><td>Frequency</td><td>Comments</td></tr></thead><tbody><tr><td rowspan="4">Automatic sun/sky/polarized/lunar photometer (ASP)</td><td>Provision of instrument-specific calibration</td><td>Calibration of reference instrument at high altitude site<br/>o Radiance and polarization calibration<br/>o Temperature sensitivity<br/>o Spare Instrument during calibration phase</td><td>Once per year</td><td rowspan="4">If instrument upgrade</td></tr><tr><td>Site performance audits with reference samples or mobile systems</td><td>Mobile instrument to transfer sky radiance between units</td><td>Each 3 months</td></tr><tr><td>Contribution to documentation and traceability of level 0 to level 2 data products</td><td></td><td>Once per year</td></tr><tr><td>Training of operators and scientists</td><td>Regular training sessions on pre-defined subjects</td><td>Twice per year</td></tr></tbody></table>
Section 4 - Concept of Centre for Aerosol Remote Sensing

<table><thead><tr><td>Technique</td><td>Type of support</td><td>Specific support</td><td>Frequency</td><td>Comments</td></tr></thead><tbody><tr><td></td><td>performance workshops</td><td></td><td></td><td></td></tr><tr><td></td><td>Training of operators and scientists</td><td>Regular training sessions on pre-defined subjects</td><td>Once per year</td><td></td></tr></tbody></table>

<table><thead><tr><td>Technique</td><td>Type of support</td><td>Specific support</td><td>Frequency</td><td>Comments</td></tr></thead><tbody><tr><td rowspan="4">Automatic sun/sky/polarized/lunar photometer (ASP)</td><td>Provision of instrument-specific calibration</td><td>Calibration of reference instrument at high altitude site<br>o Radiance and polarization calibration<br>o Temperature sensitivity<br>o Spare Instrument during calibration phase</td><td>Once per year</td><td rowspan="4">If instrument upgrade</td></tr><tr><td>Site performance audits with reference samples or mobile systems</td><td>Mobile instrument to transfer sky radiance between units</td><td>Each 3 months</td></tr><tr><td>Contribution to documentation and traceability of level 0 to level 2 data products</td><td></td><td>Once per year</td></tr><tr><td>Training of operators and scientists</td><td>Regular training sessions on pre-defined subjects</td><td>Twice per year</td></tr></tbody></table>
Operation support on request

Aerosol remote sensing NFs may face difficulties in their operation, and CARS should put in place appropriate support. This support should be offered on request. Requests for support should be addressed by the NFs to CARS, through direct communication between the PIs and the CARS Management Board (preferable by email). CARS should put in place a suitable framework for exchanging relevant information and documentation with the PIs, to prepare the operation support. CARS Management Board is responsible to prioritize and decide about the actual support to be offered ( timeline, responsible Unit, specific conditions).

<table><thead><tr><th>Technique</th><th>Type of support</th><th>Specific support</th><th>Comments</th></tr></thead><tbody><tr><td rowspan="12">Aerosol high-power lidar (AHL)</td><td rowspan="4">Provision of instrument-specific calibration</td><td>Comparison with fixed reference at calibration site</td><td>During campaigns</td></tr><tr><td>Laboratory tests</td><td></td></tr><tr><td>On-site expert visits for debugging</td><td></td></tr><tr><td>Expert analysis of the optical design</td><td></td></tr><tr><td rowspan="6">Development and provision of in-house check-up tools</td><td>Software tools for fast and dynamic assessment of the instrument alignment and signal linearity</td><td>Embedded into a hardware key or as a stand-alone software (open source)</td></tr><tr><td>Software for conversion of the QA tests into the data format for expert analysis</td><td>Embedded into a hardware key or as a stand-alone software (open source)</td></tr><tr><td>Software tools for calculation of the depolarization correction factor, overlap function, etc.</td><td>Embedded into a hardware key or as a stand-alone software (open source)</td></tr><tr><td>Software tools for data evaluation and plausibility tests</td><td>Embedded into a hardware key or as a stand-alone software (open source)</td></tr><tr><td>Software for real-time conversion of the raw signals to the SCC format, and submission of the measurements to the SCC</td><td>Embedded into a hardware key or as a stand-alone software (open source)</td></tr><tr><td>Development of data evaluation procedures and plausibility tests</td><td>Not specific at this stage</td><td>Depending on the progress of the Single Calculus Chain</td></tr><tr><td>Realization of observational site performance audits with reference samples or mobile systems</td><td>Direct comparison with a mobile reference lidar</td><td></td></tr><tr><td>Training of operators and scientists</td><td>Not specific at this stage</td><td>Depending on the specific needs</td></tr></tbody></table>
Operation support on request

Aerosol remote sensing NFs may face difficulties in their operation, and CARS should put in place appropriate support. This support should be offered on request. Requests for support should be addressed by the NFs to CARS, through direct communication between the PIs and the CARS Management Board (preferable by email). CARS should put in place a suitable framework for exchanging relevant information and documentation with the PIs, to prepare the operation support. CARS Management Board is responsible to prioritize and decide about the actual support to be offered ( timeline, responsible Unit, specific conditions).

<table><thead><tr><th>Technique</th><th>Type of support</th><th>Specific support</th><th>Comments</th></tr></thead><tbody><tr><td rowspan="12">Aerosol high-power lidar (AHL)</td><td rowspan="4">Provision of instrument-specific calibration</td><td>Comparison with fixed reference at calibration site</td><td>During campaigns</td></tr><tr><td>Laboratory tests</td><td></td></tr><tr><td>On-site expert visits for debugging</td><td></td></tr><tr><td>Expert analysis of the optical design</td><td></td></tr><tr><td rowspan="6">Development and provision of in-house check-up tools</td><td>Software tools for fast and dynamic assessment of the instrument alignment and signal linearity</td><td>Embedded into a hardware key or as a stand-alone software (open source)</td></tr><tr><td>Software for conversion of the QA tests into the data format for expert analysis</td><td>Embedded into a hardware key or as a stand-alone software (open source)</td></tr><tr><td>Software tools for calculation of the depolarization correction factor, overlap function, etc.</td><td>Embedded into a hardware key or as a stand-alone software (open source)</td></tr><tr><td>Software tools for data evaluation and plausibility tests</td><td>Embedded into a hardware key or as a stand-alone software (open source)</td></tr><tr><td>Software for real-time conversion of the raw signals to the SCC format, and submission of the measurements to the SCC</td><td>Embedded into a hardware key or as a stand-alone software (open source)</td></tr><tr><td>Development of data evaluation procedures and plausibility tests</td><td>Not specific at this stage</td><td>Depending on the progress of the Single Calculus Chain</td></tr><tr><td rowspan="2">Realization of observational site performance audits with reference samples or mobile systems</td><td>Direct comparison with a mobile reference lidar</td><td></td></tr><tr><td>Training of operators and scientists</td><td>Not specific at this stage</td><td>Depending on the specific needs</td></tr></tbody></table>
Section 4 - Concept of Centre for Aerosol Remote Sensing

<table><thead><tr><th>Technique</th><th>Type of support</th><th>Specific support</th><th>Comments</th></tr></thead><tbody><tr><td rowspan="3"></td><td rowspan="3">Consultancy for setting-up new observational or exploratory platforms and new instruments at the NFs</td><td>Consultancy regarding the instrument technical specifications</td><td></td></tr><tr><td>Consultancy regarding the set-up of the instrument on site</td><td></td></tr><tr><td>Other, not specific at this stage</td><td></td></tr><tr><td></td><td>Testing of new measurement instruments and procedures</td><td>Not specific at this stage</td><td>Depending on the progress of the technology</td></tr><tr><td></td><td>Development of retrieval algorithms or tools for producing level 1 to 3 data, including the exploitation of instrument synergies</td><td>Not specific at this stage</td><td>Depending on the progress of the Single Calculus Chain</td></tr></tbody></table>

<table><thead><tr><th>Technique</th><th>Type of support</th><th>Specific support</th><th>Comments</th></tr></thead><tbody><tr><td rowspan="10">Automatic low-power lidar / ceilometer (ALC)</td><td>Provision of instrument-specific calibration</td><td>Direct inter-comparison with a reference instrument.</td><td></td></tr><tr><td rowspan="3">Development and provision of in-house check-up tools</td><td>Monitoring of variability and trends in calibration factors and detection range</td><td></td></tr><tr><td>Calculation and monitoring of overlap functions</td><td></td></tr><tr><td>Monitoring of housekeeping data</td><td></td></tr><tr><td rowspan="2">Development of data evaluation procedures and plausibility test</td><td>Dark measurements, overlap functions, signal artefacts</td><td></td></tr><tr><td>Variability and trends of calibration factors</td><td></td></tr><tr><td>Training of operators and scientists</td><td>Not specific at this stage</td><td>Depending on the specific needs</td></tr><tr><td rowspan="2">Consultancy for setting-up new observational or exploratory platforms and new instruments at the NFs</td><td>Consultancy regarding the instrument technical specifications</td><td></td></tr><tr><td>Consultancy regarding the set-up of the instrument on site</td><td></td></tr><tr><td rowspan="2">Testing of new measurement instruments and procedures</td><td>Comparison with reference lidar</td><td></td></tr><tr><td>Comparison with previous hardware or firmware versions</td><td></td></tr></tbody></table>
Section 4 - Concept of Centre for Aerosol Remote Sensing

<table><thead><tr><th>Technique</th><th>Type of support</th><th>Specific support</th><th>Comments</th></tr></thead><tbody><tr><td rowspan="3"></td><td rowspan="3">Consultancy for setting-up new observational or exploratory platforms and new instruments at the NFs</td><td>Consultancy regarding the instrument technical specifications</td><td></td></tr><tr><td>Consultancy regarding the set-up of the instrument on site</td><td></td></tr><tr><td>Other, not specific at this stage</td><td></td></tr><tr><td></td><td>Testing of new measurement instruments and procedures</td><td>Not specific at this stage</td><td>Depending on the progress of the technology</td></tr><tr><td></td><td>Development of retrieval algorithms or tools for producing level 1 to 3 data, including the exploitation of instrument synergies</td><td>Not specific at this stage</td><td>Depending on the progress of the Single Calculus Chain</td></tr></tbody></table>

<table><thead><tr><th>Technique</th><th>Type of support</th><th>Specific support</th><th>Comments</th></tr></thead><tbody><tr><td rowspan="10">Automatic low-power lidar / ceilometer (ALC)</td><td>Provision of instrument-specific calibration</td><td>Direct inter-comparison with a reference instrument.</td><td></td></tr><tr><td rowspan="3">Development and provision of in-house check-up tools</td><td>Monitoring of variability and trends in calibration factors and detection range</td><td></td></tr><tr><td>Calculation and monitoring of overlap functions</td><td></td></tr><tr><td>Monitoring of housekeeping data</td><td></td></tr><tr><td rowspan="2">Development of data evaluation procedures and plausibility test</td><td>Dark measurements, overlap functions, signal artefacts</td><td></td></tr><tr><td>Variability and trends of calibration factors</td><td></td></tr><tr><td>Training of operators and scientists</td><td>Not specific at this stage</td><td>Depending on the specific needs</td></tr><tr><td rowspan="2">Consultancy for setting-up new observational or exploratory platforms and new instruments at the NFs</td><td>Consultancy regarding the instrument technical specifications</td><td></td></tr><tr><td>Consultancy regarding the set-up of the instrument on site</td><td></td></tr><tr><td rowspan="2">Testing of new measurement instruments and procedures</td><td>Comparison with reference lidar</td><td></td></tr><tr><td>Comparison with previous hardware or firmware versions</td><td></td></tr></tbody></table>
<table><thead><tr><td>Technique</td><td>Type of support</td><td>Specific support</td><td>Comments</td></tr></thead><tbody><tr><td></td><td></td><td>Testing the applicability and adopting of self-test tools</td><td></td></tr></tbody></table>

<table><thead><tr><td>Technique</td><td>Type of support</td><td>Specific support</td><td>Comments</td></tr></thead><tbody><tr><td rowspan="7">Automatic sun/sky/polarized/lunar photometer (ASP)</td><td>Provision of instrument-specific calibration</td><td>AOD, sky radiance and polarisation, temperature calibration<br/>Provide spare instrument during calibration</td><td></td></tr><tr><td>Realization of observational site performance audits with reference samples or mobile systems</td><td>Direct comparison with a reference system</td><td></td></tr><tr><td>Training of operators and scientists</td><td>Organization of training sessions at the TC or remote</td><td></td></tr><tr><td rowspan="2">Consultancy for setting-up new observational or exploratory platforms and new instruments at the NFs</td><td>Expert visit and discussions</td><td></td></tr><tr><td>Discussion with manufacturers</td><td></td></tr><tr><td rowspan="2">Testing of new measurement instruments and procedures</td><td>Direct comparison with a reference system</td><td></td></tr><tr><td>Characterization of parts / / prototypes in the testing laboratory</td><td></td></tr></tbody></table>
<table><thead><tr><td>Technique</td><td>Type of support</td><td>Specific support</td><td>Comments</td></tr></thead><tbody><tr><td></td><td></td><td>Testing the applicability and adopting of self-test tools</td><td></td></tr></tbody></table>

<table><thead><tr><td>Technique</td><td>Type of support</td><td>Specific support</td><td>Comments</td></tr></thead><tbody><tr><td rowspan="6">Automatic sun/sky/polarized/lunar photometer (ASP)</td><td>Provision of instrument-specific calibration</td><td>AOD, sky radiance and polarisation, temperature calibration<br/>Provide spare instrument during calibration</td><td></td></tr><tr><td>Realization of observational site performance audits with reference samples or mobile systems</td><td>Direct comparison with a reference system</td><td></td></tr><tr><td>Training of operators and scientists</td><td>Organization of training sessions at the TC or remote</td><td></td></tr><tr><td rowspan="2">Consultancy for setting-up new observational or exploratory platforms and new instruments at the NFs</td><td>Expert visit and discussions</td><td></td></tr><tr><td>Discussion with manufacturers</td><td></td></tr><tr><td rowspan="2">Testing of new measurement instruments and procedures</td><td>Direct comparison with a reference system</td><td></td></tr><tr><td>Characterization of parts / / prototypes in the testing laboratory</td><td></td></tr></tbody></table>
Section 5

Concept of the Centre for Cloud In Situ
Measurements (CIS)

ACTRIS PPP WP 4 task 4.1

22.2.2018

Public
Section 5

Concept of the Centre for Cloud In Situ
Measurements (CIS)

ACTRIS PPP WP 4 task 4.1

22.2.2018

Public
Contents

<table><tr><td>1</td><td>Purpose of the document</td><td>4</td></tr><tr><td>2</td><td>Description and role of the Centre for Cloud In Situ Measurements</td><td>4</td></tr><tr><td>2.1</td><td>Framework</td><td>4</td></tr><tr><td>2.2</td><td>Scientific relevance</td><td>5</td></tr><tr><td>2.3</td><td>Mission</td><td>5</td></tr><tr><td>3</td><td>Operation support provided to ACTRIS National Facilities</td><td>6</td></tr><tr><td>3.1</td><td>Measurement techniques covered by the Centre for Cloud In Situ Measurements, and related ACTRIS variables</td><td>6</td></tr><tr><td>3.1.1</td><td>Cloud Occurrence</td><td>7</td></tr><tr><td>3.1.2</td><td>Total Liquid Water Content and droplet effective diameter</td><td>7</td></tr><tr><td>3.1.3</td><td>Cloud Droplet Number Concentration and Size Distribution</td><td>7</td></tr><tr><td>3.1.4</td><td>Ice Particle Number Concentration and Size Distribution</td><td>8</td></tr><tr><td>3.1.5</td><td>Ice Nucleating Particle Number Concentration and Temperature Spectra</td><td>9</td></tr><tr><td>3.1.6</td><td>Droplet and Ice Residuals Number Concentration and Chemical Composition</td><td>9</td></tr><tr><td>3.1.7</td><td>Total and Interstitial Aerosol Number Concentration and Size Distribution</td><td>9</td></tr><tr><td>3.1.8</td><td>Bulk Cloud Water Chemical Composition</td><td>10</td></tr><tr><td>3.2</td><td>Estimation of the need</td><td>10</td></tr><tr><td>3.3</td><td>Timeline for implementation of the mandatory operation support</td><td>12</td></tr><tr><td>3.4</td><td>Operation support for quality assurance and quality control</td><td>15</td></tr><tr><td>3.4.1</td><td>Definition and establishment of Measurement Guidelines (MG)</td><td>15</td></tr><tr><td>3.4.2</td><td>Definition of measurement quality-assurance criteria and procedures</td><td>15</td></tr><tr><td>3.4.3</td><td>Development and provision of instrument-specific calibration</td><td>15</td></tr><tr><td>3.4.4</td><td>Development of data evaluation procedures and plausibility test</td><td>16</td></tr><tr><td>3.4.5</td><td>Realization of platform audits</td><td>16</td></tr><tr><td>3.4.6</td><td>Organization of instrument performance and operator training workshops</td><td>16</td></tr><tr><td>3.4.7</td><td>Contribution to documentation and traceability of level 0 to level 3 data products</td><td>16</td></tr><tr><td>3.5</td><td>Operation support for knowledge transfer and training</td><td>17</td></tr><tr><td>3.5.1</td><td>Training of operators and scientists</td><td>17</td></tr><tr><td>3.5.2</td><td>Consultancy for setting-up new observational or exploratory platforms and new instruments at the NFs</td><td>17</td></tr><tr><td>3.6</td><td>Operation support for improvement of measurement methodologies</td><td>17</td></tr><tr><td>3.6.1</td><td>Testing of new measurement instruments and procedures</td><td>17</td></tr><tr><td>3.6.2</td><td>Development of strategies to increase the duty cycle of instruments operated at the NFs, to reduce breakdown and maintenance downtime</td><td>17</td></tr><tr><td>3.6.3</td><td>Development of new technological products and methods</td><td>18</td></tr></table>
Contents

<table><tr><td>1</td><td>Purpose of the document</td><td>4</td></tr><tr><td>2</td><td>Description and role of the Centre for Cloud In Situ Measurements</td><td>4</td></tr><tr><td>2.1</td><td>Framework</td><td>4</td></tr><tr><td>2.2</td><td>Scientific relevance</td><td>5</td></tr><tr><td>2.3</td><td>Mission</td><td>5</td></tr><tr><td>3</td><td>Operation support provided to ACTRIS National Facilities</td><td>6</td></tr><tr><td>3.1</td><td>Measurement techniques covered by the Centre for Cloud In Situ Measurements, and related ACTRIS variables</td><td>6</td></tr><tr><td>3.1.1</td><td>Cloud Occurrence</td><td>7</td></tr><tr><td>3.1.2</td><td>Total Liquid Water Content and droplet effective diameter</td><td>7</td></tr><tr><td>3.1.3</td><td>Cloud Droplet Number Concentration and Size Distribution</td><td>7</td></tr><tr><td>3.1.4</td><td>Ice Particle Number Concentration and Size Distribution</td><td>8</td></tr><tr><td>3.1.5</td><td>Ice Nucleating Particle Number Concentration and Temperature Spectra</td><td>9</td></tr><tr><td>3.1.6</td><td>Droplet and Ice Residuals Number Concentration and Chemical Composition</td><td>9</td></tr><tr><td>3.1.7</td><td>Total and Interstitial Aerosol Number Concentration and Size Distribution</td><td>9</td></tr><tr><td>3.1.8</td><td>Bulk Cloud Water Chemical Composition</td><td>10</td></tr><tr><td>3.2</td><td>Estimation of the need</td><td>10</td></tr><tr><td>3.3</td><td>Timeline for implementation of the mandatory operation support</td><td>12</td></tr><tr><td>3.4</td><td>Operation support for quality assurance and quality control</td><td>15</td></tr><tr><td>3.4.1</td><td>Definition and establishment of Measurement Guidelines (MG)</td><td>15</td></tr><tr><td>3.4.2</td><td>Definition of measurement quality-assurance criteria and procedures</td><td>15</td></tr><tr><td>3.4.3</td><td>Development and provision of instrument-specific calibration</td><td>15</td></tr><tr><td>3.4.4</td><td>Development of data evaluation procedures and plausibility test</td><td>16</td></tr><tr><td>3.4.5</td><td>Realization of platform audits</td><td>16</td></tr><tr><td>3.4.6</td><td>Organization of instrument performance and operator training workshops</td><td>16</td></tr><tr><td>3.4.7</td><td>Contribution to documentation and traceability of level 0 to level 3 data products</td><td>16</td></tr><tr><td>3.5</td><td>Operation support for knowledge transfer and training</td><td>17</td></tr><tr><td>3.5.1</td><td>Training of operators and scientists</td><td>17</td></tr><tr><td>3.5.2</td><td>Consultancy for setting-up new observational or exploratory platforms and new instruments at the NFs</td><td>17</td></tr><tr><td>3.6</td><td>Operation support for improvement of measurement methodologies</td><td>17</td></tr><tr><td>3.6.1</td><td>Testing of new measurement instruments and procedures</td><td>17</td></tr><tr><td>3.6.2</td><td>Development of strategies to increase the duty cycle of instruments operated at the NFs, to reduce breakdown and maintenance downtime</td><td>17</td></tr><tr><td>3.6.3</td><td>Development of new technological products and methods</td><td>18</td></tr></table>
<table><tr><td>3.6.4</td><td>Development of retrieval algorithms or tools for producing level 1 to 3 data, including the exploitation of instrument synergies</td><td>18</td></tr><tr><td>4</td><td>Services provided to ACTRIS users</td><td>18</td></tr><tr><td>4.1</td><td>Estimation of the need</td><td>19</td></tr><tr><td>4.2</td><td>Provision of measurement quality assurance and quality control procedures and tools</td><td>19</td></tr><tr><td>4.3</td><td>Instrument-specific calibration</td><td>19</td></tr><tr><td>4.4</td><td>Knowledge transfer and operator training</td><td>19</td></tr><tr><td>4.5</td><td>Improvement of measurement and retrieval methodologies for aerosols, clouds, and reactive trace gases</td><td>19</td></tr><tr><td>5</td><td>Governance and management structure of the Centre for Cloud In Situ Measurements</td><td>20</td></tr><tr><td>6</td><td>Requirements for the Centre for Cloud In Situ Measurements</td><td>20</td></tr><tr><td>6.1</td><td>General requirements</td><td>20</td></tr><tr><td>6.2</td><td>Technical requirements</td><td>20</td></tr><tr><td>6.2.1</td><td>Facilities</td><td>20</td></tr><tr><td>6.2.2</td><td>Human resources</td><td>21</td></tr><tr><td>6.2.3</td><td>Other requirements</td><td>22</td></tr><tr><td>7</td><td>Basic criteria for the selection of the Centre for Cloud In Situ Measurements</td><td>22</td></tr><tr><td>8</td><td>Obligations of the Centre for Cloud In Situ Measurements</td><td>22</td></tr><tr><td>8.1</td><td>General obligations</td><td>22</td></tr><tr><td>8.2</td><td>Technical obligations</td><td>23</td></tr><tr><td>8.2.1</td><td>Technical obligations in relation with the ACTRIS National Facilities</td><td>23</td></tr><tr><td>8.2.2</td><td>Technical obligations in relation with the ACTRIS Data Centre</td><td>25</td></tr><tr><td>8.2.3</td><td>Technical obligations in relation with the Centre for Aerosol In Situ Measurements</td><td>26</td></tr><tr><td>8.2.4</td><td>Technical obligations in relation with the ACTRIS users</td><td>26</td></tr><tr><td>8.3</td><td>Evaluation of the activity of Centre for Cloud In Situ Measurements</td><td>26</td></tr><tr><td colspan="2">Glossary</td><td>28</td></tr><tr><td colspan="2">Reference documents</td><td>30</td></tr><tr><td colspan="2">Annex: Provision of the operation support</td><td>31</td></tr><tr><td colspan="2">Scheduled support</td><td>31</td></tr><tr><td colspan="2">Operation support on request</td><td>32</td></tr></table>
<table><tr><td>3.6.4</td><td>Development of retrieval algorithms or tools for producing level 1 to 3 data, including the exploitation of instrument synergies</td><td>18</td></tr><tr><td>4</td><td>Services provided to ACTRIS users</td><td>18</td></tr><tr><td>4.1</td><td>Estimation of the need</td><td>19</td></tr><tr><td>4.2</td><td>Provision of measurement quality assurance and quality control procedures and tools</td><td>19</td></tr><tr><td>4.3</td><td>Instrument-specific calibration</td><td>19</td></tr><tr><td>4.4</td><td>Knowledge transfer and operator training</td><td>19</td></tr><tr><td>4.5</td><td>Improvement of measurement and retrieval methodologies for aerosols, clouds, and reactive trace gases</td><td>19</td></tr><tr><td>5</td><td>Governance and management structure of the Centre for Cloud In Situ Measurements</td><td>20</td></tr><tr><td>6</td><td>Requirements for the Centre for Cloud In Situ Measurements</td><td>20</td></tr><tr><td>6.1</td><td>General requirements</td><td>20</td></tr><tr><td>6.2</td><td>Technical requirements</td><td>20</td></tr><tr><td>6.2.1</td><td>Facilities</td><td>20</td></tr><tr><td>6.2.2</td><td>Human resources</td><td>21</td></tr><tr><td>6.2.3</td><td>Other requirements</td><td>22</td></tr><tr><td>7</td><td>Basic criteria for the selection of the Centre for Cloud In Situ Measurements</td><td>22</td></tr><tr><td>8</td><td>Obligations of the Centre for Cloud In Situ Measurements</td><td>22</td></tr><tr><td>8.1</td><td>General obligations</td><td>22</td></tr><tr><td>8.2</td><td>Technical obligations</td><td>23</td></tr><tr><td>8.2.1</td><td>Technical obligations in relation with the ACTRIS National Facilities</td><td>23</td></tr><tr><td>8.2.2</td><td>Technical obligations in relation with the ACTRIS Data Centre</td><td>25</td></tr><tr><td>8.2.3</td><td>Technical obligations in relation with the Centre for Aerosol In Situ Measurements</td><td>26</td></tr><tr><td>8.2.4</td><td>Technical obligations in relation with the ACTRIS users</td><td>26</td></tr><tr><td>8.3</td><td>Evaluation of the activity of Centre for Cloud In Situ Measurements</td><td>26</td></tr><tr><td></td><td>Glossary</td><td>28</td></tr><tr><td></td><td>Reference documents</td><td>30</td></tr><tr><td></td><td>Annex: Provision of the operation support</td><td>31</td></tr><tr><td></td><td>Scheduled support</td><td>31</td></tr><tr><td></td><td>Operation support on request</td><td>32</td></tr></table>
# 1 Purpose of the document

This document describes the relevance, mission, requirements and obligations of the ACTRIS Centre for Cloud In Situ Measurements.

# 2 Description and role of the Centre for Cloud In Situ Measurements

## 2.1 Framework

ACTRIS is the European platform for fostering the use of research data and data analysis tools in the fields of atmospheric aerosols, clouds, and reactive trace gases. ACTRIS Central Facilities (CFs) represent the key operative entities of this Research Infrastructure (RI) and have a fundamental role as they provide operation support to the National Facilities (NFs), i.e. the observational and exploratory platforms, as well as services to the users according to the ACTRIS access policy. CFs are operated at the European level and are part of the governance and decision-making structure of the RI. Each CF may have several operational Units that can be located in the same or different locations, and are operated by research performing organizations (RPOs) or by ACTRIS ERIC.

The Centre for Cloud In Situ Measurements (CIS) is one of the six ACTRIS Topical Centres (TCs) organized around the main scientific themes of ACTRIS: aerosols, clouds, and reactive trace gases, each with a particular focus on either remote sensing or in situ measurement techniques. CIS is serving the need for cloud related weather and climate research and cloud in situ observations, as already reflected in the aerosol-cloud activities of ACTRIS-2 (WP3) and EUROCHAMP-2020 (10 and 11). The need for developing and using standardized instrument operation, data analysis, and calibration procedures is also recognized by the EUROCHAMP-2020 work package 8, which offers transnational access to four calibration facilities, with one focusing on cloud related parameters.

The future ACTRIS focus on cloud processes and cloud observations is also outlined in the description of the technical concepts for the ACTRIS observational platforms and exploratory platforms. It is foreseen that more resources are made available within the ACTRIS RI to achieve a higher coverage and higher level of the services in cooperation with the NFs to provide the highest quality level of the data. In addition, with the introduction of several units, the load of the services will be shared by several institutions in Europe which are well recognized for their high expertise in the measurement of cloud related parameters and quality management.

The cloud formation, properties and impacts depend on aerosol particles acting as cloud condensation nuclei (CCN) and ice nucleating particles (INPs). Clouds also markedly contribute to the removal of aerosol particles from the atmosphere by precipitation and scavenging processes, and they process and modify aerosols by a variety of microphysical and chemical processes. Therefore, clouds are closely linked to aerosol and reactive trace gas processes, and the activities of the Centre for Cloud in situ Measurements will closely be linked to and coordinated with the Centre for Aerosol In Situ Measurements and the Centre for Reactive Trace Gases In Situ Measurements.
# 1 Purpose of the document

This document describes the relevance, mission, requirements and obligations of the ACTRIS Centre for Cloud In Situ Measurements.

# 2 Description and role of the Centre for Cloud In Situ Measurements

## 2.1 Framework

ACTRIS is the European platform for fostering the use of research data and data analysis tools in the fields of atmospheric aerosols, clouds, and reactive trace gases. ACTRIS Central Facilities (CFs) represent the key operative entities of this Research Infrastructure (RI) and have a fundamental role as they provide operation support to the National Facilities (NFs), i.e. the observational and exploratory platforms, as well as services to the users according to the ACTRIS access policy. CFs are operated at the European level and are part of the governance and decision-making structure of the RI. Each CF may have several operational Units that can be located in the same or different locations, and are operated by research performing organizations (RPOs) or by ACTRIS ERIC.

The Centre for Cloud In Situ Measurements (CIS) is one of the six ACTRIS Topical Centres (TCs) organized around the main scientific themes of ACTRIS: aerosols, clouds, and reactive trace gases, each with a particular focus on either remote sensing or in situ measurement techniques. CIS is serving the need for cloud related weather and climate research and cloud in situ observations, as already reflected in the aerosol-cloud activities of ACTRIS-2 (WP3) and EUROCHAMP-2020 (10 and 11). The need for developing and using standardized instrument operation, data analysis, and calibration procedures is also recognized by the EUROCHAMP-2020 work package 8, which offers transnational access to four calibration facilities, with one focusing on cloud related parameters.

The future ACTRIS focus on cloud processes and cloud observations is also outlined in the description of the technical concepts for the ACTRIS observational platforms and exploratory platforms. It is foreseen that more resources are made available within the ACTRIS RI to achieve a higher coverage and higher level of the services in cooperation with the NFs to provide the highest quality level of the data. In addition, with the introduction of several units, the load of the services will be shared by several institutions in Europe which are well recognized for their high expertise in the measurement of cloud related parameters and quality management.

The cloud formation, properties and impacts depend on aerosol particles acting as cloud condensation nuclei (CCN) and ice nucleating particles (INPs). Clouds also markedly contribute to the removal of aerosol particles from the atmosphere by precipitation and scavenging processes, and they process and modify aerosols by a variety of microphysical and chemical processes. Therefore, clouds are closely linked to aerosol and reactive trace gas processes, and the activities of the Centre for Cloud in situ Measurements will closely be linked to and coordinated with the Centre for Aerosol In Situ Measurements and the Centre for Reactive Trace Gases In Situ Measurements.
## 2.2 Scientific relevance

Clouds are an important component of the atmosphere, influencing a large number of physical and chemical properties of the Earth's atmosphere and thereby strongly impacting on climate, hydrology, air quality, and ecosystems. Clouds directly influence the radiative fluxes through the atmosphere, influence the global circulation systems by latent heat effects, and are the source of precipitation in its various forms and intensities. Currently, there are large uncertainties for the cloud representation in weather and climate models and the understanding of aerosol-cloud microphysical and chemical processes is low. Furthermore, the formation, life cycles and impacts of clouds may change in a changing environment and climate through numerous processes and feedbacks. Therefore, it is of central importance to further explore cloud processes and monitor their properties and impacts over longer time periods. This will be conducted in ACTRIS National Facilities including both laboratory cloud simulation chambers (exploratory platforms) and field observatories (observational platforms).

Cloud observations in ACTRIS and preceding networks have so far focused on remote-sensing techniques, delivering information on temporal and vertical variation of cloud properties and structures. In situ observations of clouds and cloud-related parameters provide additional, very detailed insights into important processes related to the formation, the structure, and the chemical composition of clouds, which feedback to associated aerosol properties and thus impact the atmosphere as a whole. Aerosol-cloud interactions are also on the scope of previous and ongoing EUROCHAMP projects in order to extend capabilities for the operation of and the access to European atmospheric simulation chambers for exploratory work on important aerosol and cloud related processes.

Cloud in situ measurements will therefore be an important new observational component within ACTRIS. They will be performed at ground-based field stations, typically on mountains, which are frequently covered by clouds. Being a multiphase system consisting of gas, particle, liquid-water and ice phases with complex interactions, clouds represent a challenging system to study. ACTRIS cloud in situ observations will focus on a set of easily accessible variables and extend to technically more demanding parameters in the future. In contrast to other observational components, ground-based cloud in situ measurements still lack a long record of standardization efforts. These will, however, be enforced within the ACTRIS implementation phase, such that this gap will be closed and high-quality data will be ensured until the start of the operational phase of the RI in 2025.

## 2.3 Mission

The key-mission of CIS should be to offer operational support to ACTRIS NFs operating instrumentation for continuous long-term measurements of cloud occurrence, cloud water content, and cloud droplet effective diameter at observational platforms, or for episodic measurements of e.g. droplet and ice crystal size distributions, chemical cloud water composition, and ice nucleating particles during dedicated laboratory and field campaigns. While the main activities should focus on the ACTRIS community, specialized services should be offered to users from academia, business, industry, and public services depending on the respective resources.

The aim of CIS will be to develop and adapt its procedures and performance to future needs continuously responding to new research and development projects, with a focus on the operation of existing
## 2.2 Scientific relevance

Clouds are an important component of the atmosphere, influencing a large number of physical and chemical properties of the Earth's atmosphere and thereby strongly impacting on climate, hydrology, air quality, and ecosystems. Clouds directly influence the radiative fluxes through the atmosphere, influence the global circulation systems by latent heat effects, and are the source of precipitation in its various forms and intensities. Currently, there are large uncertainties for the cloud representation in weather and climate models and the understanding of aerosol-cloud microphysical and chemical processes is low. Furthermore, the formation, life cycles and impacts of clouds may change in a changing environment and climate through numerous processes and feedbacks. Therefore, it is of central importance to further explore cloud processes and monitor their properties and impacts over longer time periods. This will be conducted in ACTRIS National Facilities including both laboratory cloud simulation chambers (exploratory platforms) and field observatories (observational platforms).

Cloud observations in ACTRIS and preceding networks have so far focused on remote-sensing techniques, delivering information on temporal and vertical variation of cloud properties and structures. In situ observations of clouds and cloud-related parameters provide additional, very detailed insights into important processes related to the formation, the structure, and the chemical composition of clouds, which feedback to associated aerosol properties and thus impact the atmosphere as a whole. Aerosol-cloud interactions are also on the scope of previous and ongoing EUROCHAMP projects in order to extend capabilities for the operation of and the access to European atmospheric simulation chambers for exploratory work on important aerosol and cloud related processes.

Cloud in situ measurements will therefore be an important new observational component within ACTRIS. They will be performed at ground-based field stations, typically on mountains, which are frequently covered by clouds. Being a multiphase system consisting of gas, particle, liquid-water and ice phases with complex interactions, clouds represent a challenging system to study. ACTRIS cloud in situ observations will focus on a set of easily accessible variables and extend to technically more demanding parameters in the future. In contrast to other observational components, ground-based cloud in situ measurements still lack a long record of standardization efforts. These will, however, be enforced within the ACTRIS implementation phase, such that this gap will be closed and high-quality data will be ensured until the start of the operational phase of the RI in 2025.

## 2.3 Mission

The key-mission of CIS should be to offer operational support to ACTRIS NFs operating instrumentation for continuous long-term measurements of cloud occurrence, cloud water content, and cloud droplet effective diameter at observational platforms, or for episodic measurements of e.g. droplet and ice crystal size distributions, chemical cloud water composition, and ice nucleating particles during dedicated laboratory and field campaigns. While the main activities should focus on the ACTRIS community, specialized services should be offered to users from academia, business, industry, and public services depending on the respective resources.

The aim of CIS will be to develop and adapt its procedures and performance to future needs continuously responding to new research and development projects, with a focus on the operation of existing
instruments and methods, and the development and implementation of improved and new methods in cooperation with NFs and other TCs within their capacity and depending on their available resources.

## 3 Operation support provided to ACTRIS National Facilities

The operation support to NFs which should be provided by the CIS include:
a) procedures and tools for quality assurance and quality control of measurements and data, b) transfer of knowledge and training to operators, and c) improvements of measurement methodologies. The operation support should focus on ACTRIS variables and measurement techniques described in this concept document, also listed in the *Technical Concepts and Requirements for ACTRIS Observational and Exploratory Platforms*.

The CIS activities should include

1. establish adequate procedures and methodologies for the measurement of cloud parameters and microphysical processes at NFs;

2. perform quality assurance and quality control of the measurements and data in close cooperation with NFs and the DC;

3. ensure a high performance of NFs by conducting station audits and training sessions;

4. perform regular instrument calibration either at TC units (stationary calibration activities) or onsite by using mobile reference instruments and methods (round robin activities);

5. organise instrument and method intercomparison campaigns at both observational and exploratory platforms;

6. organise regular science, instrument and data analysis workshops;

7. promote technological development and knowledge transfer to NFs and users.

The operation support can be scheduled or on request. Participation at the scheduled activities is mandatory for the NFs. Measurements not following the mandatory actions are not considered as ACTRIS-conform and do not yield ACTRIS data. In addition, NFs may request operation support which is not scheduled, depending on the identified need. Specific operation support offered as scheduled or offered on request is detailed in *Annex: Provision of the operation support*. This annex will be updated routinely as necessary (e.g. following input from development of new testing or calibration methods and tools).

### 3.1 Measurement techniques covered by the Centre for Cloud In Situ Measurements, and related ACTRIS variables

The ACTRIS variables covered by Cloud In Situ observational and exploratory platforms should include the following variables: (1) cloud occurrence, (2) liquid water content and droplet effective diameter, (3) cloud droplet number concentration and size distribution, (4) ice particle number concentration and size distribution, (5) ice nucleating particle (INP) number concentration and temperature spectra, (6) cloud droplet and ice residuals number concentration and chemical composition, (7) total and interstitial aerosol number concentration and size distribution, and (8) bulk cloud water chemical composition.
instruments and methods, and the development and implementation of improved and new methods in cooperation with NFs and other TCs within their capacity and depending on their available resources.

## 3 Operation support provided to ACTRIS National Facilities

The operation support to NFs which should be provided by the CIS include:
a) procedures and tools for quality assurance and quality control of measurements and data, b) transfer of knowledge and training to operators, and c) improvements of measurement methodologies. The operation support should focus on ACTRIS variables and measurement techniques described in this concept document, also listed in the *Technical Concepts and Requirements for ACTRIS Observational and Exploratory Platforms*.

The CIS activities should include

1. establish adequate procedures and methodologies for the measurement of cloud parameters and microphysical processes at NFs;

2. perform quality assurance and quality control of the measurements and data in close cooperation with NFs and the DC;

3. ensure a high performance of NFs by conducting station audits and training sessions;

4. perform regular instrument calibration either at TC units (stationary calibration activities) or onsite by using mobile reference instruments and methods (round robin activities);

5. organise instrument and method intercomparison campaigns at both observational and exploratory platforms;

6. organise regular science, instrument and data analysis workshops;

7. promote technological development and knowledge transfer to NFs and users.

The operation support can be scheduled or on request. Participation at the scheduled activities is mandatory for the NFs. Measurements not following the mandatory actions are not considered as ACTRIS-conform and do not yield ACTRIS data. In addition, NFs may request operation support which is not scheduled, depending on the identified need. Specific operation support offered as scheduled or offered on request is detailed in *Annex: Provision of the operation support*. This annex will be updated routinely as necessary (e.g. following input from development of new testing or calibration methods and tools).

### 3.1 Measurement techniques covered by the Centre for Cloud In Situ Measurements, and related ACTRIS variables

The ACTRIS variables covered by Cloud In Situ observational and exploratory platforms should include the following variables: (1) cloud occurrence, (2) liquid water content and droplet effective diameter, (3) cloud droplet number concentration and size distribution, (4) ice particle number concentration and size distribution, (5) ice nucleating particle (INP) number concentration and temperature spectra, (6) cloud droplet and ice residuals number concentration and chemical composition, (7) total and interstitial aerosol number concentration and size distribution, and (8) bulk cloud water chemical composition.
### 3.1.1 Cloud Occurrence

During cloud formation, CCN activate to cloud droplets, leading to the presence of significant amount of liquid water in a given air volume. The occurrence of clouds can therefore be defined and calculated as a level 3 data product from a threshold value of liquid water content, as e.g. be measured with open path integrating cloud probes like the Particle Volume Monitor (PVM) or the Present Weather Detector (PWD). In addition to that, sites may be equipped with standard fog visibility sensors (e.g.SWS-100 or VPF-710) which may be used for data quality control of cloud microphysical instrument data products. The visibility data can also be used for the provision of level 1 cloud frequency of occurrence data and also precipitation rate and type to a first approximation.

### 3.1.2 Total Liquid Water Content and droplet effective diameter

A number of instruments are available to measure the Liquid Water Content (LWC), commonly expressed as the amount of liquid water per cubic metre of air. Instruments can be divided into two types: (i) integrating probes like the Particle Volume Monitor (PVM) and the Present Weather Detector (PWD), that integrate the scattering of cloud droplets over a given open path, and (ii) size distribution probes like the Forward Scattering Spectrometer Probe (FSSP), Fog Monitors (FM-120) and Cloud Droplet Probes (CDP), that actively operate with a controlled flow entering the probe. The most commonly used of these instruments at ground-based stations is the PVM probe, that was shown to give a stable and reliable measurement most adapted for monitoring purposes and does not suffer from bias due to the orientation of the probe into the wind direction (Guyot et al. 2015). There are approximately 5 of these instruments operating on a regular basis at ACTRIS facilities throughout Europe. These probes have been the subject of intercomparison campaigns during ACTRIS-2 (Deliverable report 3.1.2). Calibration procedures should be performed on site once a month, and instruments should be sent to the calibration centre every few years at least.

The cloud droplet effective diameter is a single variable that gives an indication on the average size of a given cloud droplet population. It is commonly derived from integrated measurements performed by PVM type instrumentation. In the PVM, the first filter converts scattered light into LWC, while the second filter converts scattered light to a signal proportional to the particle surface area density (PSA) (Gerber et al., 1994). From the ratio of these two quantities, the effective diameter is derived. These two filters guarantee a linear relationship between scattering intensity and LWC or PSA for droplets diameter from 3 to 50 µm (Gerber et al., 1994). Calibration for instrument droplet diameter is the same as that mentioned above for LWC. Recommended standard operating procedures (SOP) for cloud droplet distribution measurements have been supplied in ACTRIS 2 (Deliverable report 3.1.2). Calibration procedures should be performed on site once a month, and instruments should be sent to the calibration centre every few years at least.

### 3.1.3 Cloud Droplet Number Concentration and Size Distribution

The number size distribution of cloud droplets depends on many factors like the cloud condensation nuclei (CCN) concentration, the CCN chemical composition and the peak water supersaturation. The mean cloud droplet diameters are typically 5-15 µm, the whole size distribution typically spreads from about 1 to 100 µm. Clouds typically contain a few hundred droplets per cubic centimetre, varying from a few tens to a
3.1.1 Cloud Occurrence

During cloud formation, CCN activate to cloud droplets, leading to the presence of significant amount of
liquid water in a given air volume. The occurrence of clouds can therefore be defined and calculated as a
level 3 data product from a threshold value of liquid water content, as e.g. be measured with open path
integrating cloud probes like the Particle Volume Monitor (PVM) or the Present Weather Detector (PWD).
In addition to that, sites may be equipped with standard fog visibility sensors (e.g.SWS-100 or VPF-710)
which may be used for data quality control of cloud microphysical instrument data products. The visibility
data can also be used for the provision of level 1 cloud frequency of occurrence data and also precipitation
rate and type to a first approximation.

3.1.2 Total Liquid Water Content and droplet effective diameter

A number of instruments are available to measure the Liquid Water Content (LWC), commonly expressed as the amount of liquid water per cubic metre of air. Instruments can be divided into two types: (i) integrating probes like the Particle Volume Monitor (PVM) and the Present Weather Detector (PWD), that integrate the scattering of cloud droplets over a given open path, and (ii) size distribution probes like the Forward Scattering Spectrometer Probe (FSSP), Fog Monitors (FM-120) and Cloud Droplet Probes (CDP), that actively operate with a controlled flow entering the probe. The most commonly used of these instruments at ground-based stations is the PVM probe, that was shown to give a stable and reliable measurement most adapted for monitoring purposes and does not suffer from bias due to the orientation of the probe into the wind direction (Guyot et al. 2015). There are approximately 5 of these instruments operating on a regular basis at ACTRIS facilities throughout Europe. These probes have been the subject of intercomparison campaigns during ACTRIS-2 (Deliverable report 3.1.2). Calibration procedures should be performed on site once a month, and instruments should be sent to the calibration centre every few years at least.

The cloud droplet effective diameter is a single variable that gives an indication on the average size of a given cloud droplet population. It is commonly derived from integrated measurements performed by PVM type instrumentation. In the PVM, the first filter converts scattered light into LWC, while the second filter converts scattered light to a signal proportional to the particle surface area density (PSA) (Gerber et al., 1994). From the ratio of these two quantities, the effective diameter is derived. These two filters guarantee a linear relationship between scattering intensity and LWC or PSA for droplets diameter from 3 to 50 µm (Gerber et al., 1994). Calibration for instrument droplet diameter is the same as that mentioned above for LWC. Recommended standard operating procedures (SOP) for cloud droplet distribution measurements have been supplied in ACTRIS 2 (Deliverable report 3.1.2). Calibration procedures should be performed on site once a month, and instruments should be sent to the calibration centre every few years at least.

3.1.3 Cloud Droplet Number Concentration and Size Distribution

The number size distribution of cloud droplets depends on many factors like the cloud condensation nuclei (CCN) concentration, the CCN chemical composition and the peak water supersaturation. The mean cloud droplet diameters are typically 5-15 µm, the whole size distribution typically spreads from about 1 to 100 µm. Clouds typically contain a few hundred droplets per cubic centimetre, varying from a few tens to a
few thousands per cubic centimetre. The number size distribution of cloud droplets can be measured optically taking advance of forward scattering of light from liquid droplets. There are several so-called cloud droplet probes available, most of them are designed to be installed into aircrafts (e.g. Lance et al. 2010). Such cloud probes need special inlet arrangements to get droplets through the measurement area when applied for in situ cloud measurements. The alignment of the inlet of the probes should also be facing directly towards the wind. The probes typically measure the number size distribution between about 3 and 50 µm. Probes are usually calibrated with known sized glass beads or spinning pinholes.

### 3.1.4 Ice Particle Number Concentration and Size Distribution

These variables are important for those platforms where mixed-phase or ice clouds occur naturally, or can be investigated in simulation chambers and other laboratory experiments. They are usually measured with cloud-ice probes like the photodiode imaging spectrometers (2DS, 2DS-GS), the cloud/precipitation imaging probes (CIP-15, CIP-15, PIP), the cloud aerosol precipitation spectrometers (CAPS), the high volume precipitation spectrometer (HVPS), the CCD imaging probes (e.g. CPI, µCPI, µCOPP), the 2D spatial scattering imaging probes like the small ice detectors and phase particle discriminators (SID, PPD-2), the holographic Spectrometers (e.g. HaloHolo, Holimo), or the depolarisation particle spectrometers like the cloud aerosol spectrometer with polarisation (CAS-POL) or the backscatter cloud probe with depolarisation (BCP-D).

Cloud-ice particle phase monitoring is problematic due to the large range of particle sizes and shapes, from 1µm to 2 cm or more, and the definition of ice particle size. No one instrument can fully define the necessary ice cloud parameters and field experiments use a combination of some of the above mentioned instruments. Ice cloud parameters include ice crystal number size distribution and ice crystal shape/habit. At present, although some information on the response of the bulk cloud instrument, PVM, to ice particles is available, more work is required to deliver quantitative information, e.g. the total ice particle concentration, the ice water content (IWC), or the ice particle size distribution as accurate mixed-phase and ice cloud products. Most of the above instruments have been developed for airborne applications but have been used successfully in laboratory, chamber and ground based field applications using appropriate aspirated inlets. These have been well characterised, documented and intercompared at ground based field sites (Lloyd et al., 2015) and recommendations for specific instrument operation is available based on feedback from extensive cloud instrument workshops.

Field operation and protocols follow those for the cloud liquid water spectrometers for calibration particles and particle generator gun (Section 3.1.3), with the addition of spinning disk rigs for simulated large ice particle size, absolute ice number concentrations and ice particle shape calibration. Annual to biennial calibration and maintenance with operator training at a chamber facility is recommended using repeatable, simulated ice cloud conditions.

To deliver data assurance, a calibration and chamber simulation database for each instrument should be shared and maintained via a community data portal. This will be used for monitoring instrument performance and to pre-empt any potential instrument failure prior to field operation.
few thousands per cubic centimetre. The number size distribution of cloud droplets can be measured optically taking advance of forward scattering of light from liquid droplets. There are several so-called cloud droplet probes available, most of them are designed to be installed into aircrafts (e.g. Lance et al. 2010). Such cloud probes need special inlet arrangements to get droplets through the measurement area when applied for in situ cloud measurements. The alignment of the inlet of the probes should also be facing directly towards the wind. The probes typically measure the number size distribution between about 3 and 50 µm. Probes are usually calibrated with known sized glass beads or spinning pinholes.

### 3.1.4 Ice Particle Number Concentration and Size Distribution

These variables are important for those platforms where mixed-phase or ice clouds occur naturally, or can be investigated in simulation chambers and other laboratory experiments. They are usually measured with cloud-ice probes like the photodiode imaging spectrometers (2DS, 2DS-GS), the cloud/precipitation imaging probes (CIP-15, CIP-15, PIP), the cloud aerosol precipitation spectrometers (CAPS), the high volume precipitation spectrometer (HVPS), the CCD imaging probes (e.g. CPI, µCPI, µCOPP), the 2D spatial scattering imaging probes like the small ice detectors and phase particle discriminators (SID, PPD-2), the holographic Spectrometers (e.g. HaloHolo, Holimo), or the depolarisation particle spectrometers like the cloud aerosol spectrometer with polarisation (CAS-POL) or the backscatter cloud probe with depolarisation (BCP-D).

Cloud-ice particle phase monitoring is problematic due to the large range of particle sizes and shapes, from 1µm to 2 cm or more, and the definition of ice particle size. No one instrument can fully define the necessary ice cloud parameters and field experiments use a combination of some of the above mentioned instruments. Ice cloud parameters include ice crystal number size distribution and ice crystal shape/habit. At present, although some information on the response of the bulk cloud instrument, PVM, to ice particles is available, more work is required to deliver quantitative information, e.g. the total ice particle concentration, the ice water content (IWC), or the ice particle size distribution as accurate mixed-phase and ice cloud products. Most of the above instruments have been developed for airborne applications but have been used successfully in laboratory, chamber and ground based field applications using appropriate aspirated inlets. These have been well characterised, documented and intercompared at ground based field sites (Lloyd et al., 2015) and recommendations for specific instrument operation is available based on feedback from extensive cloud instrument workshops.

Field operation and protocols follow those for the cloud liquid water spectrometers for calibration particles and particle generator gun (Section 3.1.3), with the addition of spinning disk rigs for simulated large ice particle size, absolute ice number concentrations and ice particle shape calibration. Annual to biennial calibration and maintenance with operator training at a chamber facility is recommended using repeatable, simulated ice cloud conditions.

To deliver data assurance, a calibration and chamber simulation database for each instrument should be shared and maintained via a community data portal. This will be used for monitoring instrument performance and to pre-empt any potential instrument failure prior to field operation.
### 3.1.5 Ice Nucleating Particle Number Concentration and Temperature Spectra

Ice Nucleating Particles (INPs) can currently only episodically be measured with aerosol sampling based methods and offline analysis of the temperature spectra of ambient concentrations. These methods have a poor time resolution of only a few hours to a few days, but can deliver accurate INP concentrations in the temperature range from about -5°C to -25°C. These techniques, though relatively labour intensive, should be used for both exploratory and observational ACTRIS activities, but require a thorough assessment and calibration of the aerosol sampling methods (e.g. filters or impingers) and the INP analysis systems. Furthermore, the storage of the samples as well as their shipment to the laboratory should be standardized to assure comparability between different sampling locations and systems. It is anticipated that in the near future new INP instruments with higher time resolution and more automated operation may be available. The CIS has to provide guidance for such new developments and develop calibration protocols and procedures.

### 3.1.6 Droplet and Ice Residuals Number Concentration and Chemical Composition

Special inlets with inertial separation of large hydrometeors form smaller, interstitial aerosol particles, so-called counterflow virtual impactors (CVI), have been developed and designed in order to selectively sample droplets and ice particles into dry, particle-free air, evaporate the condensed water and analyse the residual particles with various techniques (Ogren et al., 1985; Noone et al., 1988; Twohey et al., 1997; Mertes et al., 2001). Based on the CVI principle, Boulter et al. (2006) have developed a pumped CVI (PCVI) with for stationary operation at both laboratory and observational platforms. This device has cut-of diameters of only a few µm for separating small cloud droplets and ice crystals from interstitial aerosols. It was further improved and modified towards the larger ice-selective PCVI (IS-PCVI) with cut-off diameters larger than 10 µm for separating ice crystals from droplets in mixed-phase clouds (Hiranuma et al., 2016). The residuals can either be sampled for offline physical and chemical analysis, e.g. with electron microscopy (Worringen et al., 2015), or directly be analysed with proper instruments like condensation particle counters or single particle mass spectrometers continuously sampling from the PCVI (Cziczo et al., 2009). PCVI residual sampling and analysis provides valuable insight into the formation mechanisms of droplets and ice crystals, but require proper control and maintenance for setup, sampling connection and operation procedures in order to achieve high quality data.

### 3.1.7 Total and Interstitial Aerosol Number Concentration and Size Distribution

The simultaneous measurement of the total and interstitial aerosol particle size distribution provides the opportunity to derive the activation diameter (D50) and (with assumption or knowledge of the particle hygroscopicity) the maximum supersaturation (Smax) of the cloud (e.g. Krüger et al., 2014). Both parameters are important for cloud microphysical modelling purposes (Reutter et al., 2009). The needed size distribution of the activated particles (cloud condensation nuclei, CCN) is then inferred by the difference of the total and interstitial particle size distribution. Both direct in situ observations require the combination of a dedicated inlet and an aerosol sizing instrument, which is able to measure down to at least 20 nm.

This approach was already successfully applied in numerous in situ cloud studies (Anttila et al., 2009; Anttila et al., 2012; Asmi et al., 2012; Ditas et al., 2012; Hammer et al., 2014; Henning et al. 2002a) at
### 3.1.5 Ice Nucleating Particle Number Concentration and Temperature Spectra

Ice Nucleating Particles (INPs) can currently only episodically be measured with aerosol sampling based methods and offline analysis of the temperature spectra of ambient concentrations. These methods have a poor time resolution of only a few hours to a few days, but can deliver accurate INP concentrations in the temperature range from about -5°C to -25°C. These techniques, though relatively labour intensive, should be used for both exploratory and observational ACTRIS activities, but require a thorough assessment and calibration of the aerosol sampling methods (e.g. filters or impingers) and the INP analysis systems. Furthermore, the storage of the samples as well as their shipment to the laboratory should be standardized to assure comparability between different sampling locations and systems. It is anticipated that in the near future new INP instruments with higher time resolution and more automated operation may be available. The CIS has to provide guidance for such new developments and develop calibration protocols and procedures.

### 3.1.6 Droplet and Ice Residuals Number Concentration and Chemical Composition

Special inlets with inertial separation of large hydrometeors form smaller, interstitial aerosol particles, so-called counterflow virtual impactors (CVI), have been developed and designed in order to selectively sample droplets and ice particles into dry, particle-free air, evaporate the condensed water and analyse the residual particles with various techniques (Ogren et al., 1985; Noone et al., 1988; Twohey et al., 1997; Mertes et al., 2001). Based on the CVI principle, Boulter et al. (2006) have developed a pumped CVI (PCVI) with for stationary operation at both laboratory and observational platforms. This device has cut-of diameters of only a few µm for separating small cloud droplets and ice crystals from interstitial aerosols. It was further improved and modified towards the larger ice-selective PCVI (IS-PCVI) with cut-off diameters larger than 10 µm for separating ice crystals from droplets in mixed-phase clouds (Hiranuma et al., 2016). The residuals can either be sampled for offline physical and chemical analysis, e.g. with electron microscopy (Worringen et al., 2015), or directly be analysed with proper instruments like condensation particle counters or single particle mass spectrometers continuously sampling from the PCVI (Cziczo et al., 2009). PCVI residual sampling and analysis provides valuable insight into the formation mechanisms of droplets and ice crystals, but require proper control and maintenance for setup, sampling connection and operation procedures in order to achieve high quality data.

### 3.1.7 Total and Interstitial Aerosol Number Concentration and Size Distribution

The simultaneous measurement of the total and interstitial aerosol particle size distribution provides the opportunity to derive the activation diameter (D50) and (with assumption or knowledge of the particle hygroscopicity) the maximum supersaturation (Smax) of the cloud (e.g. Krüger et al., 2014). Both parameters are important for cloud microphysical modelling purposes (Reutter et al., 2009). The needed size distribution of the activated particles (cloud condensation nuclei, CCN) is then inferred by the difference of the total and interstitial particle size distribution. Both direct in situ observations require the combination of a dedicated inlet and an aerosol sizing instrument, which is able to measure down to at least 20 nm.

This approach was already successfully applied in numerous in situ cloud studies (Anttila et al., 2009; Anttila et al., 2012; Asmi et al., 2012; Ditas et al., 2012; Hammer et al., 2014; Henning et al. 2002a) at
different research field stations (Jungfraujoch, Pallas, Puy-de-Dome). The dedicated total and interstitial
inlets used at these field sites were individual versions and thus their sampling specifications might be
different. For future cloud studies, the total inlet should follow the design of Weingartner et al. (1999) to
sample particles up to a size of 40 µm for wind speeds up to 20 m s⁻¹. The interstitial inlet should have a
sharp cut-off at 2.5 µm either as a cyclone (Verheggen et al., 2007) or an impactor (Schwarzenböck et al.,
2000).

The second component is the aerosol particle size distribution measurement device. In order to derive the D50 at high supersaturation and the presence of highly soluble aerosol particles, the scanning mobility particle sizer (SMPS) would be the best choice for this purpose. This kind of size distribution instrument is frequently intercompared, calibrated and technically standardized (Wiedensohler et al., 2012) and the respective standards and SOPs are defined by the aerosol in-situ TC and will need to be followed. Both inlets and SMPS systems can be operated in an autonomous way, so that their deployment are proposed as a minimum requirement at each future cloud station. Standards and SOPs regarding the inlets and the aerosol instruments connected to them will be developed and supported by the TC for Aerosol In Situ Measurements.

3.1.8 Bulk Cloud Water Chemical Composition

The chemical composition of cloud water is most often determined from bulk cloud water collectors, which rely on the principle of droplet inertial impaction and the collection of impacted droplets of all sizes into one collection vessel. For passive samplers (e.g. Reynolds et al., 1996), droplet impaction typically takes place on strings or meshes and is driven by the ambient wind only. So-called rotating arm collectors force droplet impaction by rotating a rod around its centre point at high speed (e.g. Krämer und Schütz 1994). In other active samplers, droplet-laden air is drawn through the device to ensure sufficient droplet velocities for impaction even under calm conditions. Impaction then takes place on a set of vertically clamped strings (e.g. Demoz et al., 1996) or on flat surfaces (e.g. Berner 1988). As active samplers show less dependency of collection efficiencies on wind speeds, they are the preferred instruments for ground-based cloud water sampling. After sampling, the integral cloud water sample is typically analysed off-line, i.e. in a laboratory away from the sampling device, for its chemical composition. For inorganic ions, ion chromatography is most often applied, while for the organic composition a range of analytical separation techniques are available, including gas and liquid chromatography and capillary electrophoresis, coupled either to optical or mass spectrometry detectors. Such combinations have been frequently applied in cloud chemistry campaigns (e.g. Collett et al., 1990; Lihavainen et al., 2008; Marinoni et al., 2004; van Pinxteren et al., 2005) and efforts to harmonise and standardise both the collection and the chemical analysis will be reinforced within the ACTRIS pre-operational phase to define standards and SOPs for the determination of cloud water chemical composition.

## 3.2 Estimation of the need

In Europe, more than 10 observational sites are currently operating instruments for physical or chemical
doud characterisation on a continuous or episodic way. In addition, 4 ACTRIS exploratory platforms
perform cloud experiments and extend their cloud simulation capabilities as part of EUROCHAMP-2020.
For INP measurements, about 15 groups in Europe develop and use offline techniques based on aerosol
sampling, and more than 10 in situ sampling instruments are used or currently developed for field
different research field stations (Jungfraujoch, Pallas, Puy-de-Dome). The dedicated total and interstitial
inlets used at these field sites were individual versions and thus their sampling specifications might be
different. For future cloud studies, the total inlet should follow the design of Weingartner et al. (1999) to
sample particles up to a size of 40 µm for wind speeds up to 20 m s⁻¹. The interstitial inlet should have a
sharp cut-off at 2.5 µm either as a cyclone (Verheggen et al., 2007) or an impactor (Schwarzenböck et al.,
2000).

The second component is the aerosol particle size distribution measurement device. In order to derive the D50 at high supersaturation and the presence of highly soluble aerosol particles, the scanning mobility particle sizer (SMPS) would be the best choice for this purpose. This kind of size distribution instrument is frequently intercompared, calibrated and technically standardized (Wiedensohler et al., 2012) and the respective standards and SOPs are defined by the aerosol in-situ TC and will need to be followed. Both inlets and SMPS systems can be operated in an autonomous way, so that their deployment are proposed as a minimum requirement at each future cloud station. Standards and SOPs regarding the inlets and the aerosol instruments connected to them will be developed and supported by the TC for Aerosol In Situ Measurements.

3.1.8 Bulk Cloud Water Chemical Composition

The chemical composition of cloud water is most often determined from bulk cloud water collectors, which rely on the principle of droplet inertial impaction and the collection of impacted droplets of all sizes into one collection vessel. For passive samplers (e.g. Reynolds et al., 1996), droplet impaction typically takes place on strings or meshes and is driven by the ambient wind only. So-called rotating arm collectors force droplet impaction by rotating a rod around its centre point at high speed (e.g. Krämer und Schütz 1994). In other active samplers, droplet-laden air is drawn through the device to ensure sufficient droplet velocities for impaction even under calm conditions. Impaction then takes place on a set of vertically clamped strings (e.g. Demoz et al., 1996) or on flat surfaces (e.g. Berner 1988). As active samplers show less dependency of collection efficiencies on wind speeds, they are the preferred instruments for ground-based cloud water sampling. After sampling, the integral cloud water sample is typically analysed off-line, i.e. in a laboratory away from the sampling device, for its chemical composition. For inorganic ions, ion chromatography is most often applied, while for the organic composition a range of analytical separation techniques are available, including gas and liquid chromatography and capillary electrophoresis, coupled either to optical or mass spectrometry detectors. Such combinations have been frequently applied in cloud chemistry campaigns (e.g. Collett et al., 1990; Lihavainen et al., 2008; Marinoni et al., 2004; van Pinxteren et al., 2005) and efforts to harmonise and standardise both the collection and the chemical analysis will be reinforced within the ACTRIS pre-operational phase to define standards and SOPs for the determination of cloud water chemical composition.

## 3.2 Estimation of the need

In Europe, more than 10 observational sites are currently operating instruments for physical or chemical
doud characterisation on a continuous or episodic way. In addition, 4 ACTRIS exploratory platforms
perform cloud experiments and extend their cloud simulation capabilities as part of EUROCHAMP-2020.
For INP measurements, about 15 groups in Europe develop and use offline techniques based on aerosol
sampling, and more than 10 in situ sampling instruments are used or currently developed for field
observations. About 5 teams have started to develop or already fly cloud in situ instrumentation on unmanned aerial vehicles (UAVs) for remotely piloted activities around or even inside clouds with both in situ measurements of cloud relevant variables and sampling of aerosols for offline INP analysis. This sector has a high potential for future research and monitoring tasks and the need for operational support, QA/QC issues and technological developments will largely grow during the next years.

With cloud in-situ measurements being a new ACTRIS activity, the number of sites and groups operating in this area is expected to significantly grow over time with continued efforts of CIS and NFs to provide measurement guidelines and operational support. The following table gives an estimates on the number of ACTRIS NFs operating cloud in situ instruments. It is based on number of existing platforms and their activities as well as information about potential ACTRIS activities listed in the first version of the Stakeholder Handbook 2017:

<table><thead><tr><th rowspan="3">Measurement technique</th><th colspan="3">Number of ACTRIS National Facilities to which CIS should provide operational support</th></tr><tr><th rowspan="2">Now (preparatory phase, by 2020)</th><th colspan="2">by 2025</th></tr><tr><th>Min.</th><th>Max.</th></tr></thead><tbody><tr><td>Integrating cloud probes</td><td>10</td><td>12</td><td>15</td></tr><tr><td>Cloud droplet probes</td><td>10</td><td>12</td><td>15</td></tr><tr><td>Cloud ice probes</td><td>5</td><td>5</td><td>10</td></tr><tr><td>Ice nucleating particle instruments</td><td>5</td><td>10</td><td>15</td></tr><tr><td>Droplet and ice selective PCVI</td><td>3</td><td>3</td><td>5</td></tr><tr><td>Total and interstitial aerosol inlets</td><td>10</td><td>12</td><td>15</td></tr><tr><td>Bulk cloud water chemical analysis</td><td>5</td><td>5</td><td>10</td></tr></tbody></table>
observations. About 5 teams have started to develop or already fly cloud in situ instrumentation on unmanned aerial vehicles (UAVs) for remotely piloted activities around or even inside clouds with both in situ measurements of cloud relevant variables and sampling of aerosols for offline INP analysis. This sector has a high potential for future research and monitoring tasks and the need for operational support, QA/QC issues and technological developments will largely grow during the next years.

With cloud in-situ measurements being a new ACTRIS activity, the number of sites and groups operating in this area is expected to significantly grow over time with continued efforts of CIS and NFs to provide measurement guidelines and operational support. The following table gives an estimates on the number of ACTRIS NFs operating cloud in situ instruments. It is based on number of existing platforms and their activities as well as information about potential ACTRIS activities listed in the first version of the Stakeholder Handbook 2017:

<table><thead><tr><th rowspan="3">Measurement technique</th><th colspan="3">Number of ACTRIS National Facilities to which CIS should provide operational support</th></tr><tr><th rowspan="2">Now (preparatory phase, by 2020)</th><th colspan="2">by 2025</th></tr><tr><th>Min.</th><th>Max.</th></tr></thead><tbody><tr><td>Integrating cloud probes</td><td>10</td><td>12</td><td>15</td></tr><tr><td>Cloud droplet probes</td><td>10</td><td>12</td><td>15</td></tr><tr><td>Cloud ice probes</td><td>5</td><td>5</td><td>10</td></tr><tr><td>Ice nucleating particle instruments</td><td>5</td><td>10</td><td>15</td></tr><tr><td>Droplet and ice selective PCVI</td><td>3</td><td>3</td><td>5</td></tr><tr><td>Total and interstitial aerosol inlets</td><td>10</td><td>12</td><td>15</td></tr><tr><td>Bulk cloud water chemical analysis</td><td>5</td><td>5</td><td>10</td></tr></tbody></table>
## 3.3 Timeline for implementation of the mandatory operation support

Considering the ACTRIS roadmap, CIS should consider the following implementation plan for the mandatory operation support (including general tasks, scheduled and on request operation support, see Annex: Provision of the operation support):

<table><thead><tr><th rowspan="2">Operation support</th><th rowspan="2">Type</th><th>Preparation phase</th><th>Implementation phase</th><th>Operation phase</th></tr><tr><th>&lt; 2020</th><th>2020 - 2025</th><th>&gt; 2025</th></tr></thead><tbody><tr><td>SOPs</td><td>General task</td><td>Basic SOPs for operation of the instruments (minimum requirements)</td><td>New SOPs for operation of advanced instruments (optimum setup)</td><td>Updates and new SOPs</td></tr><tr><td rowspan="2">QA criteria & procedures</td><td>General task</td><td>Basic procedures for controlling the quality of the measurements (minimum requirements)</td><td>New procedures for controlling the quality of the advanced measurements (optimum setup)</td><td>Updates and new procedures</td></tr><tr><td>General task</td><td>Quality-assurance criteria for basic measurements (minimum requirements)</td><td>New quality-assurance criteria for advanced measurements (minimum requirements) (optimum setup)</td><td>Updates and new quality-assurance criteria</td></tr><tr><td rowspan="3">Instrument-specific calibration</td><td>On request</td><td>Direct comparison with fixed, state-of-the-art reference instruments</td><td>Continue as support on request</td><td>Continue as support on request</td></tr><tr><td>On request</td><td>Tests and direct comparison with mobile reference instruments and methods</td><td>Tests at CIS laboratories or using mobile instruments</td><td>Continue as support on request</td></tr><tr><td>On request</td><td></td><td>On-site expert inspection of the instruments</td><td>Continue as support on request</td></tr><tr><td rowspan="2">In-house check-up tools</td><td>General task</td><td></td><td>Tools for rapid assessment of critical behaviour of the instrument</td><td>Updates</td></tr><tr><td>General task</td><td></td><td>Software for automatic submission of level 0 data</td><td>Updates</td></tr></tbody></table>
## 3.3 Timeline for implementation of the mandatory operation support

Considering the ACTRIS roadmap, CIS should consider the following implementation plan for the mandatory operation support (including general tasks, scheduled and on request operation support, see Annex: Provision of the operation support):

<table><thead><tr><th rowspan="2">Operation support</th><th rowspan="2">Type</th><th>Preparation phase</th><th>Implementation phase</th><th>Operation phase</th></tr><tr><th>&lt; 2020</th><th>2020 - 2025</th><th>&gt; 2025</th></tr></thead><tbody><tr><td>SOPs</td><td>General task</td><td>Basic SOPs for operation of the instruments (minimum requirements)</td><td>New SOPs for operation of advanced instruments (optimum setup)</td><td>Updates and new SOPs</td></tr><tr><td rowspan="2">QA criteria & procedures</td><td>General task</td><td>Basic procedures for controlling the quality of the measurements (minimum requirements)</td><td>New procedures for controlling the quality of the advanced measurements (optimum setup)</td><td>Updates and new procedures</td></tr><tr><td>General task</td><td>Quality-assurance criteria for basic measurements (minimum requirements)</td><td>New quality-assurance criteria for advanced measurements (minimum requirements) (optimum setup)</td><td>Updates and new quality-assurance criteria</td></tr><tr><td rowspan="3">Instrument-specific calibration</td><td>On request</td><td>Direct comparison with fixed, state-of-the-art reference instruments</td><td>Continue as support on request</td><td>Continue as support on request</td></tr><tr><td>On request</td><td>Tests and direct comparison with mobile reference instruments and methods</td><td>Tests at CIS laboratories or using mobile instruments</td><td>Continue as support on request</td></tr><tr><td>On request</td><td></td><td>On-site expert inspection of the instruments</td><td>Continue as support on request</td></tr><tr><td rowspan="2">In-house check-up tools</td><td>General task</td><td></td><td>Tools for rapid assessment of critical behaviour of the instrument</td><td>Updates</td></tr><tr><td>General task</td><td></td><td>Software for automatic submission of level 0 data</td><td>Updates</td></tr></tbody></table>
<table><thead><tr><th rowspan="2">Operation support</th><th rowspan="2">Type</th><th>Preparation phase</th><th>Implementation phase</th><th>Operation phase</th></tr><tr><th>&lt; 2020</th><th>2020 - 2025</th><th>&gt; 2025</th></tr></thead><tbody><tr><td>Data evaluation procedures and plausibility test</td><td>General task</td><td></td><td>Software for rapid assessment of the measurements' quality</td><td>Updates</td></tr><tr><td>Site performance audits with reference samples or mobile systems</td><td>Scheduled</td><td>Direct comparison with mobile reference instruments</td><td>Continue as scheduled activity</td><td>Continue as scheduled activity</td></tr><tr><td>Instrument performance workshops</td><td>Scheduled</td><td>Annual assessment of the site performance through expert analysis of specific QA test results</td><td>Continue as scheduled activity</td><td>Continue as scheduled activity</td></tr><tr><td>Documentation and traceability</td><td>Scheduled</td><td></td><td>Codification of the results of the QA tests</td><td>Continue as scheduled activity</td></tr><tr><td rowspan="4">Training</td><td>Scheduled</td><td></td><td>Regular training sessions on pre-defined subjects</td><td>Continue as scheduled activity</td></tr><tr><td>On request</td><td>Training during parallel activities (direct comparisons, audits, calibration)</td><td>Continue as support on request</td><td>Continue as support on request</td></tr><tr><td>Scheduled</td><td>Documentation available on the CIS website: instrument setup, QC, QA protocols, operation and optimization of the instruments and data management</td><td>Continue as needed</td><td>Continue as needed</td></tr><tr><td>Scheduled</td><td></td><td>Forums, webinars</td><td>Continue as needed</td></tr><tr><td rowspan="2">Consultancy</td><td>On request</td><td>Upgrading of the instruments, establishment of new observing stations, development of new exploratory platforms</td><td>Continue as support on request</td><td>Continue as support on request</td></tr><tr><td>On request</td><td></td><td>Specific observation protocols</td><td>Continue as support on request</td></tr></tbody></table>

ACTRIS PPP (www.actris.eu) is supported by the European Commission under the Horizon 2020 – Research and Innovation Framework Programme, H2020-INFRADEV-2016-2017, Grant Agreement number: 739530
<table><thead><tr><th rowspan="2">Operation support</th><th rowspan="2">Type</th><th>Preparation phase</th><th>Implementation phase</th><th>Operation phase</th></tr><tr><th>&lt; 2020</th><th>2020 - 2025</th><th>&gt; 2025</th></tr></thead><tbody><tr><td>Data evaluation procedures and plausibility test</td><td>General task</td><td></td><td>Software for rapid assessment of the measurements' quality</td><td>Updates</td></tr><tr><td>Site performance audits with reference samples or mobile systems</td><td>Scheduled</td><td>Direct comparison with mobile reference instruments</td><td>Continue as scheduled activity</td><td>Continue as scheduled activity</td></tr><tr><td>Instrument performance workshops</td><td>Scheduled</td><td>Annual assessment of the site performance through expert analysis of specific QA test results</td><td>Continue as scheduled activity</td><td>Continue as scheduled activity</td></tr><tr><td>Documentation and traceability</td><td>Scheduled</td><td></td><td>Codification of the results of the QA tests</td><td>Continue as scheduled activity</td></tr><tr><td rowspan="4">Training</td><td>Scheduled</td><td></td><td>Regular training sessions on pre-defined subjects</td><td>Continue as scheduled activity</td></tr><tr><td>On request</td><td>Training during parallel activities (direct comparisons, audits, calibration)</td><td>Continue as support on request</td><td>Continue as support on request</td></tr><tr><td>Scheduled</td><td>Documentation available on the CIS website: instrument setup, QC, QA protocols, operation and optimization of the instruments and data management</td><td>Continue as needed</td><td>Continue as needed</td></tr><tr><td>Scheduled</td><td></td><td>Forums, webinars</td><td>Continue as needed</td></tr><tr><td rowspan="2">Consultancy</td><td>On request</td><td>Upgrading of the instruments, establishment of new observing stations, development of new exploratory platforms</td><td>Continue as support on request</td><td>Continue as support on request</td></tr><tr><td>On request</td><td></td><td>Specific observation protocols</td><td>Continue as support on request</td></tr></tbody></table>

ACTRIS PPP (www.actris.eu) is supported by the European Commission under the Horizon 2020 – Research and Innovation Framework Programme, H2020-INFRADEV-2016-2017, Grant Agreement number: 739530
Section 5 – Centre for Cloud In Situ Measurements

<table><thead><tr><th rowspan="2">Operation support</th><th rowspan="2">Type</th><th>Preparation phase</th><th>Implementation phase</th><th>Operation phase</th></tr><tr><th>&lt; 2020</th><th>2020 - 2025</th><th>&gt; 2025</th></tr></thead><tbody><tr><td>Testing of new instruments and procedures</td><td>On request</td><td></td><td>Testing of prototypes</td><td>Continue as support on request</td></tr></tbody></table>

ACTRIS PPP (www.actris.eu) is supported by the European Commission under the Horizon 2020 – Research and Innovation Framework Programme, H2020-INFRADEV-2016-2017, Grant Agreement number: 739530
Section 5 – Centre for Cloud In Situ Measurements

<table><thead><tr><th rowspan="2">Operation support</th><th rowspan="2">Type</th><th>Preparation phase</th><th>Implementation phase</th><th>Operation phase</th></tr><tr><th>&lt; 2020</th><th>2020 - 2025</th><th>&gt; 2025</th></tr></thead><tbody><tr><td>Testing of new instruments and procedures</td><td>On request</td><td></td><td>Testing of prototypes</td><td>Continue as support on request</td></tr></tbody></table>

ACTRIS PPP (www.actris.eu) is supported by the European Commission under the Horizon 2020 – Research and Innovation Framework Programme, H2020-INFRADEV-2016-2017, Grant Agreement number: 739530
## 3.4 Operation support for quality assurance and quality control

### 3.4.1 Definition and establishment of Measurement Guidelines (MG)

The observation of cloud in situ parameters on a continuous basis is still new to most observational sites. Therefore, it will be one of the first tasks of the respective units of CIS to define respective procedures and protocols and support the observational platforms to implement continuous observations.

So far, cloud in situ activities have mostly been performed on a campaign-like basis. In order to improve and test instruments, and to achieve high international standards of respective research, intercomparison campaigns for cloud probes, INP instruments, and water vapour instruments have been conducted both at field sites and in the laboratory. Such instrument and method oriented campaigns will also be an important activity of CIS and will regularly be organized for instruments that can be shipped to the respective platform and operated together with the other participating instruments. The participation in these activities is mandatory for all instruments operated at ACTRIS observational and exploratory platforms.

The objective should be to compile state-of-the-art measurement guidelines (MG) for each instrument operated either continuously or episodically at cloud in situ platforms. This will be achieved in close collaboration among the NF instruments experts with the CIS as competence centre coordinating the relevant expert knowledge transfer and having a leading role in writing and reviewing state-of-the-art MGs. The MGs should include a description of the measurement techniques and procedures as well as all fields of QA and QC of measurements, calibrations, data evaluation and data delivery. These MGs define how ACTRIS measurements of the corresponding variables should be performed in order to achieve the ACTIRS label. The CIS will decide in consultancy with the ACTRIS assemblies of NFs and the Research Infrastructure Committee about revisions and the development of new MGs.

### 3.4.2 Definition of measurement quality-assurance criteria and procedures

Measurement quality-assurance criteria and procedures should be included in the corresponding MGs and Standard Operation Procedures (SOPs). The QA processes are assumed to be similar for the different variables and techniques.

Briefly, the QA processes should combine:

* Implementing and following the MGs for measurements, data processing, data delivery and documentation.

* Participating instrument calibration and inter-comparison activities proposed by CIS.

* Using transfer standards for on-site calibration as developed and coordinated by CIS.

* Establishing plausibility plots and evaluations.

* Contributing to data quality workshops and to station performance audits.

* Participating in training activities.

### 3.4.3 Development and provision of instrument-specific calibration

* Instrument-specific calibration should be achieved by CIS in one of the following ways:

* calibration to laboratory standards and reference instruments in respective units of CIS,

* on site comparison and calibration to travelling reference instruments, and

* round-robin or side-by-side intercomparison activities.
## 3.4 Operation support for quality assurance and quality control

### 3.4.1 Definition and establishment of Measurement Guidelines (MG)

The observation of cloud in situ parameters on a continuous basis is still new to most observational sites. Therefore, it will be one of the first tasks of the respective units of CIS to define respective procedures and protocols and support the observational platforms to implement continuous observations.

So far, cloud in situ activities have mostly been performed on a campaign-like basis. In order to improve and test instruments, and to achieve high international standards of respective research, intercomparison campaigns for cloud probes, INP instruments, and water vapour instruments have been conducted both at field sites and in the laboratory. Such instrument and method oriented campaigns will also be an important activity of CIS and will regularly be organized for instruments that can be shipped to the respective platform and operated together with the other participating instruments. The participation in these activities is mandatory for all instruments operated at ACTRIS observational and exploratory platforms.

The objective should be to compile state-of-the-art measurement guidelines (MG) for each instrument operated either continuously or episodically at cloud in situ platforms. This will be achieved in close collaboration among the NF instruments experts with the CIS as competence centre coordinating the relevant expert knowledge transfer and having a leading role in writing and reviewing state-of-the-art MGs. The MGs should include a description of the measurement techniques and procedures as well as all fields of QA and QC of measurements, calibrations, data evaluation and data delivery. These MGs define how ACTRIS measurements of the corresponding variables should be performed in order to achieve the ACTIRS label. The CIS will decide in consultancy with the ACTRIS assemblies of NFs and the Research Infrastructure Committee about revisions and the development of new MGs.

### 3.4.2 Definition of measurement quality-assurance criteria and procedures

Measurement quality-assurance criteria and procedures should be included in the corresponding MGs and Standard Operation Procedures (SOPs). The QA processes are assumed to be similar for the different variables and techniques.

Briefly, the QA processes should combine:

* Implementing and following the MGs for measurements, data processing, data delivery and documentation.

* Participating instrument calibration and inter-comparison activities proposed by CIS.

* Using transfer standards for on-site calibration as developed and coordinated by CIS.

* Establishing plausibility plots and evaluations.

* Contributing to data quality workshops and to station performance audits.

* Participating in training activities.

### 3.4.3 Development and provision of instrument-specific calibration

* Instrument-specific calibration should be achieved by CIS in one of the following ways:

* calibration to laboratory standards and reference instruments in respective units of CIS,

* on site comparison and calibration to travelling reference instruments, and

* round-robin or side-by-side intercomparison activities.
### 3.4.4 Development of data evaluation procedures and plausibility test

A number of evaluations procedures and plausibility tests have already been developed and tested in activities related to ACTRIS and EUROCHAMP projects. Data evaluation procedures and plausibility tests should be further developed for all of the mentioned measurement techniques hand-in-hand with the measurement quality assurance criteria in order to enable stations to perform mature plausibility checks and develop a good understanding of the quality of the data. This should be an ongoing activity of the CIS.

Common data analysis tools for calibration to laboratory standards, comparison to travelling reference instruments, and the participation in round-robin and side-by-side intercomparisons will be maintained and improved to take into account new knowledge. Training in use of these tools should be provided.

### 3.4.5 Realization of platform audits

Site performance audits with reference samples (for INP and optical instruments) or mobile systems should be provided by the CIS. A period between station visits of 1 year should be envisioned and should be supplemented by calibration checks, round robin exercises, target-gas checks and intercomparison experiments. New stations and stations encountering problems with data quality and data flow should get more frequent audits upon necessity.

The performance audits check the conformity of a station to the QA requirements as specified in this document and the corresponding MGs. The reference for conformity of a station should evolve as the QA system evolves. During the audit at a station the following parts should be evaluated:

* The sampling and instrument set-up.

* The calibration systems.

* The QA/QC procedures implemented.

* The training and instructions sessions.

* The data delivery.

* The results from intercomparison exercises.

* The uncertainty evaluation.

* The logbooks (instrument, measurements, station).

* The scientific use of the data.

* The overall equipment of the station.

### 3.4.6 Organization of instrument performance and operator training workshops

Yearly QA/QC workshops checking the plausibility and quality of the NF data should be performed. The objective is the conformity with the DQOs as defined in the MGs. That should include assessments of the year-to-year consistency of the reported data, within network station-to-station consistency, for both observational and exploratory platforms. Instrument performance and training workshops are envisioned on a regular bases aiming at a 2-year period.

### 3.4.7 Contribution to documentation and traceability of level 0 to level 3 data products

The CIS should define together with the DC the data submission templates for the NFs according to the data flow documents developed between the DC and the CIS. This should include reporting the measurement uncertainty evaluated according the MGs in order to assess the quality level of the data and to track any change in data quality. These documents, the MGs, and the data submission procedures
### 3.4.4 Development of data evaluation procedures and plausibility test

A number of evaluations procedures and plausibility tests have already been developed and tested in activities related to ACTRIS and EUROCHAMP projects. Data evaluation procedures and plausibility tests should be further developed for all of the mentioned measurement techniques hand-in-hand with the measurement quality assurance criteria in order to enable stations to perform mature plausibility checks and develop a good understanding of the quality of the data. This should be an ongoing activity of the CIS.

Common data analysis tools for calibration to laboratory standards, comparison to travelling reference instruments, and the participation in round-robin and side-by-side intercomparisons will be maintained and improved to take into account new knowledge. Training in use of these tools should be provided.

### 3.4.5 Realization of platform audits

Site performance audits with reference samples (for INP and optical instruments) or mobile systems should be provided by the CIS. A period between station visits of 1 year should be envisioned and should be supplemented by calibration checks, round robin exercises, target-gas checks and intercomparison experiments. New stations and stations encountering problems with data quality and data flow should get more frequent audits upon necessity.

The performance audits check the conformity of a station to the QA requirements as specified in this document and the corresponding MGs. The reference for conformity of a station should evolve as the QA system evolves. During the audit at a station the following parts should be evaluated:

* The sampling and instrument set-up.

* The calibration systems.

* The QA/QC procedures implemented.

* The training and instructions sessions.

* The data delivery.

* The results from intercomparison exercises.

* The uncertainty evaluation.

* The logbooks (instrument, measurements, station).

* The scientific use of the data.

* The overall equipment of the station.

### 3.4.6 Organization of instrument performance and operator training workshops

Yearly QA/QC workshops checking the plausibility and quality of the NF data should be performed. The objective is the conformity with the DQOs as defined in the MGs. That should include assessments of the year-to-year consistency of the reported data, within network station-to-station consistency, for both observational and exploratory platforms. Instrument performance and training workshops are envisioned on a regular bases aiming at a 2-year period.

### 3.4.7 Contribution to documentation and traceability of level 0 to level 3 data products

The CIS should define together with the DC the data submission templates for the NFs according to the data flow documents developed between the DC and the CIS. This should include reporting the measurement uncertainty evaluated according the MGs in order to assess the quality level of the data and to track any change in data quality. These documents, the MGs, and the data submission procedures
regulate the appropriate documentation of the data. All the references on the used calibration procedures and materials should be reported as meta-data together with each data submission. In addition, bias and repeatability/reproducibility of targeted cloud in situ measurements and in round robin measurements, as well as results of intercomparisons should be made available in the data base.

## 3.5 Operation support for knowledge transfer and training

### 3.5.1 Training of operators and scientists

For improving and maintaining high data quality in the ACTRIS cloud in situ network it is essential to train on a regular basis operators and scientists of the NFs. In training workshops with thematic training courses, the necessary expertise should be shared with the corresponding station staff. The annual concept of the training schedule should be developed together with the NFs. Objectives of the training should cover all aspects of the MGs, QA/QC procedures and data management. Beside the specific training centres, the data QC workshops, the audits, and the side-by-side intercomparisons should be used for training. Besides teaching of technical aspects of the instruments, the training should also provide knowledge about basics of cloud microphysics and sampling issues in clouds, so that the trainees will be able to identify suspicious data features and sampling artefacts.

### 3.5.2 Consultancy for setting-up new observational or exploratory platforms and new instruments at the NFs

The CIS should identify gaps in the measurement network in Europe. Thus, CIS should provide the respective consultancy to the corresponding decision bodies in ACTRIS. Furthermore, the CIS should consult new stations in setting up their monitoring infrastructure and quality management system. Consultancy is provided via the MGs, direct communication, reference station visits, and visits of the new to build stations. Consultancy will be available from the beginning of the implementation phase.

## 3.6 Operation support for improvement of measurement methodologies

### 3.6.1 Testing of new measurement instruments and procedures

The CIS should track new developments in measuring and analysing cloud variables and ice nucleating particles and should be involved in testing and developing new instrumentation for assessing the ACTRIS cloud in situ variables. Specifically, the suitability of new instruments for long-term monitoring within ACTRIS and the conformity with DQOs should be tested and characterized. Recommendations of the suitability of new measurement technologies for achieving high data quality in the ACTRSI-RI should be provided. For this activity, specific joint-projects should be envisaged considering further the maturity of the new technologies. During the topical NFs assemblies, initiatives or requirements towards new instrumentation can be discussed and decided. The presently intended new techniques include the continuous and highly time-resolved measurement of INP concentrations as a function of temperature.

### 3.6.2 Development of strategies to increase the duty cycle of instruments operated at the NFs, to reduce breakdown and maintenance downtime

The CIS should contribute to develop optimised methods and procedures in order to reduce breakdown and maintenance times to ensure maximum possible operation time of the continuously operated instruments.
regulate the appropriate documentation of the data. All the references on the used calibration procedures and materials should be reported as meta-data together with each data submission. In addition, bias and repeatability/reproducibility of targeted cloud in situ measurements and in round robin measurements, as well as results of intercomparisons should be made available in the data base.

## 3.5 Operation support for knowledge transfer and training

### 3.5.1 Training of operators and scientists

For improving and maintaining high data quality in the ACTRIS cloud in situ network it is essential to train on a regular basis operators and scientists of the NFs. In training workshops with thematic training courses, the necessary expertise should be shared with the corresponding station staff. The annual concept of the training schedule should be developed together with the NFs. Objectives of the training should cover all aspects of the MGs, QA/QC procedures and data management. Beside the specific training centres, the data QC workshops, the audits, and the side-by-side intercomparisons should be used for training. Besides teaching of technical aspects of the instruments, the training should also provide knowledge about basics of cloud microphysics and sampling issues in clouds, so that the trainees will be able to identify suspicious data features and sampling artefacts.

### 3.5.2 Consultancy for setting-up new observational or exploratory platforms and new instruments at the NFs

The CIS should identify gaps in the measurement network in Europe. Thus, CIS should provide the respective consultancy to the corresponding decision bodies in ACTRIS. Furthermore, the CIS should consult new stations in setting up their monitoring infrastructure and quality management system. Consultancy is provided via the MGs, direct communication, reference station visits, and visits of the new to build stations. Consultancy will be available from the beginning of the implementation phase.

## 3.6 Operation support for improvement of measurement methodologies

### 3.6.1 Testing of new measurement instruments and procedures

The CIS should track new developments in measuring and analysing cloud variables and ice nucleating particles and should be involved in testing and developing new instrumentation for assessing the ACTRIS cloud in situ variables. Specifically, the suitability of new instruments for long-term monitoring within ACTRIS and the conformity with DQOs should be tested and characterized. Recommendations of the suitability of new measurement technologies for achieving high data quality in the ACTRSI-RI should be provided. For this activity, specific joint-projects should be envisaged considering further the maturity of the new technologies. During the topical NFs assemblies, initiatives or requirements towards new instrumentation can be discussed and decided. The presently intended new techniques include the continuous and highly time-resolved measurement of INP concentrations as a function of temperature.

### 3.6.2 Development of strategies to increase the duty cycle of instruments operated at the NFs, to reduce breakdown and maintenance downtime

The CIS should contribute to develop optimised methods and procedures in order to reduce breakdown and maintenance times to ensure maximum possible operation time of the continuously operated instruments.
### 3.6.3 Development of new technological products and methods

The CIS should be involved in the development of new measurement techniques, technological products and methods by the NFs. Depending on the situation, the CIS may recommend to the ACTRIS RI Committee to decide on the implementation of such new techniques at the RI level. The Centre has no obligation to develop the full set of operation support for such new techniques, unless they are embraced by ACTRIS and implemented as part of the NFs.

### 3.6.4 Development of retrieval algorithms or tools for producing level 1 to 3 data, including the exploitation of instrument synergies

The CIS should contribute to developments of optimised procedures for level 1 and 2 products with automated quality test tools.

## 4 Services provided to ACTRIS users

An ACTRIS user is a person, a team, or an institution using either ACTRIS data or any other ACTRIS service. ACTRIS users originate from academia, business, industry and public services, from ACTRIS member countries as well as from countries, which are not ACTRIS members, inside and outside Europe. All user employing or developing instruments for measuring the ACTRIS variables in reactive trace gases may benefit from the QA/QC capabilities developed and available for service by the CIS.

Access to some ACTRIS services is open and free, most importantly the access to ACTRIS data, data products, and digital tools provided by the DC, which is the point of entry for free ACTRIS data services. Other access to ACTRIS services is considered competitive, based on the CIS capacity, and will require a review process that is centrally managed by the HO/SAMU. SAMU is the single point of entry for user access to all TC services and to some specific services and data products provided by the DC. Access is regulated by both the ACTRIS access policy and the ACTRIS data policy, respectively.

Within the CIS, service provided to ACTRIS users is only provided in a restricted manner considering the limited resources of the TC, the service fee covered by the user, and the priority to ACTRIS NFs support. The units of CIS will decide about provision of services to users. CIS should agree on these issues with SAMU.
### 3.6.3 Development of new technological products and methods

The CIS should be involved in the development of new measurement techniques, technological products and methods by the NFs. Depending on the situation, the CIS may recommend to the ACTRIS RI Committee to decide on the implementation of such new techniques at the RI level. The Centre has no obligation to develop the full set of operation support for such new techniques, unless they are embraced by ACTRIS and implemented as part of the NFs.

### 3.6.4 Development of retrieval algorithms or tools for producing level 1 to 3 data, including the exploitation of instrument synergies

The CIS should contribute to developments of optimised procedures for level 1 and 2 products with automated quality test tools.

## 4 Services provided to ACTRIS users

An ACTRIS user is a person, a team, or an institution using either ACTRIS data or any other ACTRIS service. ACTRIS users originate from academia, business, industry and public services, from ACTRIS member countries as well as from countries, which are not ACTRIS members, inside and outside Europe. All user employing or developing instruments for measuring the ACTRIS variables in reactive trace gases may benefit from the QA/QC capabilities developed and available for service by the CIS.

Access to some ACTRIS services is open and free, most importantly the access to ACTRIS data, data products, and digital tools provided by the DC, which is the point of entry for free ACTRIS data services. Other access to ACTRIS services is considered competitive, based on the CIS capacity, and will require a review process that is centrally managed by the HO/SAMU. SAMU is the single point of entry for user access to all TC services and to some specific services and data products provided by the DC. Access is regulated by both the ACTRIS access policy and the ACTRIS data policy, respectively.

Within the CIS, service provided to ACTRIS users is only provided in a restricted manner considering the limited resources of the TC, the service fee covered by the user, and the priority to ACTRIS NFs support. The units of CIS will decide about provision of services to users. CIS should agree on these issues with SAMU.
## 4.1 Estimation of the need

The CIS is able to schedule some of its potential capabilities for service to ACTRIS users. Table 4-1 summarises the current availability estimates.

<table><caption>Table 4-1: The CIS service estimation for potential ACTRIS users</caption><thead><tr><th rowspan="3">Type of ACTRIS user</th><th colspan="3">Number of users to which ACTRIS is providing services</th></tr><tr><th rowspan="2">Now</th><th colspan="2">by 2025</th></tr><tr><th>Min.</th><th>Max.</th></tr></thead><tbody><tr><td>Academia</td><td>80</td><td>80</td><td>150</td></tr><tr><td>Business / Industry</td><td>5</td><td>5</td><td>10</td></tr><tr><td>Public Services</td><td>0</td><td>5</td><td>10</td></tr></tbody></table>

## 4.2 Provision of measurement quality assurance and quality control procedures and tools

The CIS should offer all documents and data-plausibility control procedures to users. Furthermore, depending on resources, CIS should offer participation in round-robin, side-by-side intercomparison and yearly data quality control workshops. In individual cases and on short-term, also calibration of laboratory standards and the provision of calibration or reference materials may be offered to users. However, on long-term, such stations should become part of the ACTRIS RI.

## 4.3 Instrument-specific calibration

The CIS can offer, depending on resources, calibration of laboratory standards, comparison to travelling reference instruments, and the participation in round-robin and side-by-side intercomparisons which should be used to check the calibration and performance of the instruments including ambient samples under realistic measurement conditions. Besides this, instruments for ice nucleating particles can be calibrated by on-site reference aerosols.

## 4.4 Knowledge transfer and operator training

As outlined in 3.4.1, also knowledge transfer and training for users can be offered by CIS in restricted extent, mainly depending on resources, with priority for ACTRIS NFs support.

## 4.5 Improvement of measurement and retrieval methodologies for aerosols, clouds, and reactive trace gases

The CIS can contribute to developments relevant for specific requirements arising from the aerosol-cloud-reactive trace gases interaction, i.e. when processes at the boundaries of respective atmospheric states require the observation of new variables.
## 4.1 Estimation of the need

The CIS is able to schedule some of its potential capabilities for service to ACTRIS users. Table 4-1 summarises the current availability estimates.

<table><caption>Table 4-1: The CIS service estimation for potential ACTRIS users</caption><thead><tr><th rowspan="3">Type of ACTRIS user</th><th colspan="3">Number of users to which ACTRIS is providing services</th></tr><tr><th rowspan="2">Now</th><th colspan="2">by 2025</th></tr><tr><th>Min.</th><th>Max.</th></tr></thead><tbody><tr><td>Academia</td><td>80</td><td>80</td><td>150</td></tr><tr><td>Business / Industry</td><td>5</td><td>5</td><td>10</td></tr><tr><td>Public Services</td><td>0</td><td>5</td><td>10</td></tr></tbody></table>

## 4.2 Provision of measurement quality assurance and quality control procedures and tools

The CIS should offer all documents and data-plausibility control procedures to users. Furthermore, depending on resources, CIS should offer participation in round-robin, side-by-side intercomparison and yearly data quality control workshops. In individual cases and on short-term, also calibration of laboratory standards and the provision of calibration or reference materials may be offered to users. However, on long-term, such stations should become part of the ACTRIS RI.

## 4.3 Instrument-specific calibration

The CIS can offer, depending on resources, calibration of laboratory standards, comparison to travelling reference instruments, and the participation in round-robin and side-by-side intercomparisons which should be used to check the calibration and performance of the instruments including ambient samples under realistic measurement conditions. Besides this, instruments for ice nucleating particles can be calibrated by on-site reference aerosols.

## 4.4 Knowledge transfer and operator training

As outlined in 3.4.1, also knowledge transfer and training for users can be offered by CIS in restricted extent, mainly depending on resources, with priority for ACTRIS NFs support.

## 4.5 Improvement of measurement and retrieval methodologies for aerosols, clouds, and reactive trace gases

The CIS can contribute to developments relevant for specific requirements arising from the aerosol-cloud-reactive trace gases interaction, i.e. when processes at the boundaries of respective atmospheric states require the observation of new variables.
# 5 Governance and management structure of the Centre for Cloud In Situ Measurements

The CIS shall be organized in different units according to the specific role of each unit in addressing the ACTRIS variables, assuring that CIS complies with the requirements and obligations described in sections 6 and 8 of this document, and considering the general principles described in the *Baseline document for the concept of the Central Facilities*. The Centre for Cloud In Situ Measurements shall be organized such that:

* It has a well-defined structure of Units,

* It has a well-defined decision-making process,

* It is coordinated by a CF Director and managed by a CF Management Board, which consists of the CF Director and the CF Unit Heads,

* It has clear and cost-efficient task sharing between the Units,

* It has a risk management strategy,

* It participates in the ACTRIS decision making by sending representative(s) to the ACTRIS legal entity bodies, e.g. to the RI committee.

# 6 Requirements for the Centre for Cloud In Situ Measurements

## 6.1 General requirements

In order to be labelled as the Centre for Cloud In Situ Measurements, the candidate shall:

* Commit for long-term operation, at least 10 years starting with the next year after the implementation as a TC,

* Set-up an appropriate structure of Units, to ensure an adequate functionality of the CF, cost-effective operation, and scalability with respect to the user demands and advancement of the state-of-the-art technology,

* Demonstrate the capacity (in terms of material and personnel resources), to ensure the provision of the needed services and operation support, as described in section 6.2

* Provide a feasible implementation and operation plan for the first five years, starting with the next year after the selection as CF,

* Commit to provide a minimum amount of user services, as described in section 4

* Commit to provide the mandatory operation support to the ACTRIS NFs, as described in section 3.

## 6.2 Technical requirements

### 6.2.1 Facilities

The CIS should share the tasks between different units. All units should be established in well recognized institutes with long-term experience in the field of aerosol-cloud exploratory studies or continuous long-term monitoring of aerosol-cloud processes and cloud variables in the atmosphere. The various units should contribute with their specific and complementary competences to achieve a share of the multiple tasks. Sharing the tasks is necessary because no unit itself has all the needed resources. The number of
# 5 Governance and management structure of the Centre for Cloud In Situ Measurements

The CIS shall be organized in different units according to the specific role of each unit in addressing the ACTRIS variables, assuring that CIS complies with the requirements and obligations described in sections 6 and 8 of this document, and considering the general principles described in the *Baseline document for the concept of the Central Facilities*. The Centre for Cloud In Situ Measurements shall be organized such that:

* It has a well-defined structure of Units,

* It has a well-defined decision-making process,

* It is coordinated by a CF Director and managed by a CF Management Board, which consists of the CF Director and the CF Unit Heads,

* It has clear and cost-efficient task sharing between the Units,

* It has a risk management strategy,

* It participates in the ACTRIS decision making by sending representative(s) to the ACTRIS legal entity bodies, e.g. to the RI committee.

# 6 Requirements for the Centre for Cloud In Situ Measurements

## 6.1 General requirements

In order to be labelled as the Centre for Cloud In Situ Measurements, the candidate shall:

* Commit for long-term operation, at least 10 years starting with the next year after the implementation as a TC,

* Set-up an appropriate structure of Units, to ensure an adequate functionality of the CF, cost-effective operation, and scalability with respect to the user demands and advancement of the state-of-the-art technology,

* Demonstrate the capacity (in terms of material and personnel resources), to ensure the provision of the needed services and operation support, as described in section 6.2

* Provide a feasible implementation and operation plan for the first five years, starting with the next year after the selection as CF,

* Commit to provide a minimum amount of user services, as described in section 4

* Commit to provide the mandatory operation support to the ACTRIS NFs, as described in section 3.

## 6.2 Technical requirements

### 6.2.1 Facilities

The CIS should share the tasks between different units. All units should be established in well recognized institutes with long-term experience in the field of aerosol-cloud exploratory studies or continuous long-term monitoring of aerosol-cloud processes and cloud variables in the atmosphere. The various units should contribute with their specific and complementary competences to achieve a share of the multiple tasks. Sharing the tasks is necessary because no unit itself has all the needed resources. The number of
units should be reasonably balanced between available resources, competence and capacity, and
enhanced coordinative and administrative work.

All units shall be able to provide calibration, QA/QC, and training services as outlined above. Otherwise,
the intended services shall be complimentary, with the coordinating unit having capacity and know-how
in the majority of services proposed.

The basic facilities required at the different CIS units are

* cloud simulation chambers for the calibration and intercomparison of cloud droplet and ice probes at well controlled cloud formation conditions (all probes sampling from the same cloud parcel),

* sufficient indoor (for exploratory platform) or outdoor (for observational platform) space for mounting a large number of instruments during instrument intercomparison activities,

* training facilities with reference measurement systems the unit is in charge of,

* set-ups for travelling reference instruments or reference aerosol systems.

* offices for participants in calibration and intercomparison activities.

* Meeting rooms to host training and knowledge transfer workshops.

With respect to mobile reference instruments and materials, transport in the EU should easily be feasible.
The location of different units in different European countries would shorten transport and travel distance
to the NFs and to coordinated activities and assemblies.

## 6.2.2 Human resources

Regarding the operation support and service provision for the cloud in situ measurements techniques as outlined in section 3, the CIS may be structured in 3 to 4 units located at laboratory and observational platforms, which may need the following human resources:

<table><thead><tr><th rowspan="2"></th><th colspan="3">Scientific & technical staff</th><th colspan="3">Management & administration staff</th></tr><tr><th>Scientific expert</th><th>Qualified operator</th><th>Technician</th><th>Expert manager</th><th>Qualified officer</th><th>Administrative assistant</th></tr></thead><tbody><tr><th>All</th><td>1</td><td>3</td><td>3</td><td>0.4</td><td>0.4</td><td></td></tr></tbody></table>

The needed human resources were estimated on the basis of the proposed activities. Numbers are expressed in FTE units.

The scientific and technical staff should have the necessary expertise to operate the facilities, instruments and IT infrastructure of CIS, and to develop and provide the operation support and services described above. As a minimum they should have:

* expert scientists: >5 years of experience in related field

* engineer/qualified operator/engineer: >3 years of experience

* technician: > 1 year of experience

* expert manager, qualified officer, and administrative assistance: at least 3 years of experience in the administrative area.
units should be reasonably balanced between available resources, competence and capacity, and
enhanced coordinative and administrative work.

All units shall be able to provide calibration, QA/QC, and training services as outlined above. Otherwise,
the intended services shall be complimentary, with the coordinating unit having capacity and know-how
in the majority of services proposed.

The basic facilities required at the different CIS units are

* cloud simulation chambers for the calibration and intercomparison of cloud droplet and ice probes at well controlled cloud formation conditions (all probes sampling from the same cloud parcel),

* sufficient indoor (for exploratory platform) or outdoor (for observational platform) space for mounting a large number of instruments during instrument intercomparison activities,

* training facilities with reference measurement systems the unit is in charge of,

* set-ups for travelling reference instruments or reference aerosol systems.

* offices for participants in calibration and intercomparison activities.

* Meeting rooms to host training and knowledge transfer workshops.

With respect to mobile reference instruments and materials, transport in the EU should easily be feasible.
The location of different units in different European countries would shorten transport and travel distance
to the NFs and to coordinated activities and assemblies.

### 6.2.2 Human resources

Regarding the operation support and service provision for the cloud in situ measurements techniques as outlined in section 3, the CIS may be structured in 3 to 4 units located at laboratory and observational platforms, which may need the following human resources:

<table><thead><tr><th rowspan="2"></th><th colspan="3">Scientific & technical staff</th><th colspan="3">Management & administration staff</th></tr><tr><th>Scientific expert</th><th>Qualified operator</th><th>Technician</th><th>Expert manager</th><th>Qualified officer</th><th>Administrative assistant</th></tr></thead><tbody><tr><th>All</th><td>1</td><td>3</td><td>3</td><td>0.4</td><td>0.4</td><td></td></tr></tbody></table>

The needed human resources were estimated on the basis of the proposed activities. Numbers are expressed in FTE units.

The scientific and technical staff should have the necessary expertise to operate the facilities, instruments and IT infrastructure of CIS, and to develop and provide the operation support and services described above. As a minimum they should have:

* expert scientists: >5 years of experience in related field

* engineer/qualified operator/engineer: >3 years of experience

* technician: > 1 year of experience

* expert manager, qualified officer, and administrative assistance: at least 3 years of experience in the administrative area.
### 6.2.3 Other requirements

Not applicable

## 7 Basic criteria for the selection of the Centre for Cloud In Situ Measurements

The applications to host the Centre for Cloud In Situ Measurements are evaluated against a set of criteria covering:

* The level of commitment for long-term operation

* The capacity to provide the operational support and the services described in sections 3 and 4

* The availability of the necessary laboratories, instruments, equipment

* The availability of human resources (no., expertise)

* The efficiency in providing the operational support and the services

* The feasibility of the implementation plan (costs, resources, timeline)

* The feasibility of the operation plan (methodology, costs per service)

* The level of maturity

* Status of the development of the Units

* No. of existing users

* Adequacy of the decision-making

* Risk management strategy

These criteria will be detailed in the associated call documents.

## 8 Obligations of the Centre for Cloud In Situ Measurements

### 8.1 General obligations

The following general obligations shall apply to the Centre for Cloud In Situ Measurements while operational:

* To organize its activities in a cost-efficient way, timely, and with high quality,

* To actively participate in the governance and sustainable development of ACTRIS,

* To provide services to users, according to the access procedures, availability of time, and material resources,

* To provide operation support to the NFs, according to the identified needs, agreed schedules, and procedures,

* To implement efficient user interaction activities by:

* Organizing workshops, to interact with users,

* Collecting user feed-backs,

* Maintaining the CF and ACTRIS websites,

* To document its activities, accesses provided, key performance indicators, and finances, and provide this information to the HO,

* To contribute to minimize and assess the uncertainties related to data and data products, according to their role and in collaboration with each other,

* To remain at the forefront of the technology for Cloud In Situ measurements.
### 6.2.3 Other requirements

Not applicable

## 7 Basic criteria for the selection of the Centre for Cloud In Situ Measurements

The applications to host the Centre for Cloud In Situ Measurements are evaluated against a set of criteria covering:

* The level of commitment for long-term operation

* The capacity to provide the operational support and the services described in sections 3 and 4

* The availability of the necessary laboratories, instruments, equipment

* The availability of human resources (no., expertise)

* The efficiency in providing the operational support and the services

* The feasibility of the implementation plan (costs, resources, timeline)

* The feasibility of the operation plan (methodology, costs per service)

* The level of maturity

* Status of the development of the Units

* No. of existing users

* Adequacy of the decision-making

* Risk management strategy

These criteria will be detailed in the associated call documents.

## 8 Obligations of the Centre for Cloud In Situ Measurements

### 8.1 General obligations

The following general obligations shall apply to the Centre for Cloud In Situ Measurements while operational:

* To organize its activities in a cost-efficient way, timely, and with high quality,

* To actively participate in the governance and sustainable development of ACTRIS,

* To provide services to users, according to the access procedures, availability of time, and material resources,

* To provide operation support to the NFs, according to the identified needs, agreed schedules, and procedures,

* To implement efficient user interaction activities by:

* Organizing workshops, to interact with users,

* Collecting user feed-backs,

* Maintaining the CF and ACTRIS websites,

* To document its activities, accesses provided, key performance indicators, and finances, and provide this information to the HO,

* To contribute to minimize and assess the uncertainties related to data and data products, according to their role and in collaboration with each other,

* To remain at the forefront of the technology for Cloud In Situ measurements.
## 8.2 Technical obligations

### 8.2.1 Technical obligations in relation with the ACTRIS National Facilities

Technical obligations of the Centre for Cloud In Situ Measurements in relation with the ACTRIS National Facilities refer strictly to the measurement techniques described in this concept document and in *Technical concepts and requirements for ACTRIS Observational Platforms and Exploratory Platforms*. The operation of other techniques at the NFs does not imply a technical obligation for the Centre for Cloud In Situ Measurements to provide operation support. New techniques / instrument types are only accepted as ACTRIS instruments after the approval of the RI Committee and after the development of the associated QA procedures by the CF.

ACTRIS NFs are responsible for controlling the quality of their measurements by:

* Applying the SOPs and QA procedures, and using in a proper manner the in-house check-up tools developed by CIS

* Participating to all scheduled QA activities described in Annex: Provision of the operation support - Scheduled support

* Notifying CIS, and requesting access to specialized services described in Annex: Provision of the operation support - Operation support on request, whenever the instrument is not performing well or a major upgrade has been made

CIS, on the other hand, is responsible to provide the mandatory operation support to all corresponding NFs, and maintain a continuous collaboration with the operators and scientists at the NFs, in order to facilitate the control of the measurements quality.

#### 8.2.1.1 Guidelines, quality assurance criteria and procedures

The Centre for Cloud In Situ Measurements is responsible for the quality assurance procedures and guidelines of the ACTRIS measurements conducted at the NFs with measurement techniques as described in Section 3.1. For this, CIS should implement the following operation support for each of the measurement techniques under its topics:

* Definition and establishment of standard operation procedures;

* Definition of measurement quality-assurance criteria and procedures.

All the procedures, guidelines, quality assurance criteria, plausibility tests, etc. should be documented and accessible to all related NFs. Specific training sessions with the related NF operators should be organized to ensure a smooth and correct implementation of the above.

#### 8.2.1.2 Tools, tests and consultancy for quality control of the measurements

It is duty of the Centre for Cloud In Situ Measurements to assist the related NFs in the quality control of their measurements by providing the operation support listed in the previous sections, specifically:

* Development and provision of instrument-specific calibration;

* Development and provision of in-house check-up tools;

* Development of data evaluation procedures and plausibility test;

* Consultancy for setting-up new observational or exploratory platforms and new instruments at the NFs;

* Testing of new measurement instruments and procedures.
## 8.2 Technical obligations

### 8.2.1 Technical obligations in relation with the ACTRIS National Facilities

Technical obligations of the Centre for Cloud In Situ Measurements in relation with the ACTRIS National Facilities refer strictly to the measurement techniques described in this concept document and in *Technical concepts and requirements for ACTRIS Observational Platforms and Exploratory Platforms*. The operation of other techniques at the NFs does not imply a technical obligation for the Centre for Cloud In Situ Measurements to provide operation support. New techniques / instrument types are only accepted as ACTRIS instruments after the approval of the RI Committee and after the development of the associated QA procedures by the CF.

ACTRIS NFs are responsible for controlling the quality of their measurements by:

* Applying the SOPs and QA procedures, and using in a proper manner the in-house check-up tools developed by CIS

* Participating to all scheduled QA activities described in Annex: Provision of the operation support - Scheduled support

* Notifying CIS, and requesting access to specialized services described in Annex: Provision of the operation support - Operation support on request, whenever the instrument is not performing well or a major upgrade has been made

CIS, on the other hand, is responsible to provide the mandatory operation support to all corresponding NFs, and maintain a continuous collaboration with the operators and scientists at the NFs, in order to facilitate the control of the measurements quality.

#### 8.2.1.1 Guidelines, quality assurance criteria and procedures

The Centre for Cloud In Situ Measurements is responsible for the quality assurance procedures and guidelines of the ACTRIS measurements conducted at the NFs with measurement techniques as described in Section 3.1. For this, CIS should implement the following operation support for each of the measurement techniques under its topics:

* Definition and establishment of standard operation procedures;

* Definition of measurement quality-assurance criteria and procedures.

All the procedures, guidelines, quality assurance criteria, plausibility tests, etc. should be documented and accessible to all related NFs. Specific training sessions with the related NF operators should be organized to ensure a smooth and correct implementation of the above.

#### 8.2.1.2 Tools, tests and consultancy for quality control of the measurements

It is duty of the Centre for Cloud In Situ Measurements to assist the related NFs in the quality control of their measurements by providing the operation support listed in the previous sections, specifically:

* Development and provision of instrument-specific calibration;

* Development and provision of in-house check-up tools;

* Development of data evaluation procedures and plausibility test;

* Consultancy for setting-up new observational or exploratory platforms and new instruments at the NFs;

* Testing of new measurement instruments and procedures.
This operation support should be offered to the related NFs whenever there is a need, or a significant
progress in the development of these tools, and accompanied by the appropriate training given that
sufficient resources are available at the CIS.

8.2.1.3 Assessment of performances, measurement flagging

The Centre for Cloud In Situ Measurements is mandated to assist the Data Centre and the related NFs in
the quality control of the measurements and data, by:

* Realization of observational site performance audits with reference samples or mobile systems;

* Organizing regular exercises to assess the performances of the NFs, including instrument performance workshops;

* Contributing to documentation and traceability of level 0 to level 3 data products.

The activities involving directly the NFs operating instruments for measuring cloud variables and INPs covered by the TC should be scheduled by the TC and provided regularly. The corresponding NFs should participate in these activities according to the plan proposed by the Centre for Cloud In Situ Measurements and agreed on with the ACTRIS Scientific Advisory Board (SAB).

8.2.1.4 Transfer of knowledge and training

In addition to the training organized for the implementation of guidelines, procedures, and tools
developed in support of QA/QC of the measurements and data, the Centre for Cloud In Situ
Measurements should organize training sessions with the NFs as needed.

8.2.1.5 Improvement of measurement methodologies for the Centre for Cloud In Situ Measurements

Although it is not an obligation, the Centre for Cloud In Situ Measurements should work to sustain a high
level of performance and to stimulate the advancement of new techniques and methodologies for
measuring cloud variables and INPs in the atmosphere by:

* Development of strategies to increase the duty cycle of instruments operated at the NFs, to reduce breakdown and maintenance downtime;

* Development of new technological products and methods;

* Development of retrieval algorithms or tools for producing level 1 to 3 data, including the exploitation of instrument synergies;

* Organizing regular events (at least once every 2 years) and other forums, in order to exchange knowledge with the NFs and other scientists;

* Contributing to CEN, ISO, or similar standardization activities.
This operation support should be offered to the related NFs whenever there is a need, or a significant
progress in the development of these tools, and accompanied by the appropriate training given that
sufficient resources are available at the CIS.

8.2.1.3 Assessment of performances, measurement flagging

The Centre for Cloud In Situ Measurements is mandated to assist the Data Centre and the related NFs in
the quality control of the measurements and data, by:

* Realization of observational site performance audits with reference samples or mobile systems;

* Organizing regular exercises to assess the performances of the NFs, including instrument performance workshops;

* Contributing to documentation and traceability of level 0 to level 3 data products.

The activities involving directly the NFs operating instruments for measuring cloud variables and INPs covered by the TC should be scheduled by the TC and provided regularly. The corresponding NFs should participate in these activities according to the plan proposed by the Centre for Cloud In Situ Measurements and agreed on with the ACTRIS Scientific Advisory Board (SAB).

8.2.1.4 Transfer of knowledge and training

In addition to the training organized for the implementation of guidelines, procedures, and tools
developed in support of QA/QC of the measurements and data, the Centre for Cloud In Situ
Measurements should organize training sessions with the NFs as needed.

8.2.1.5 Improvement of measurement methodologies for the Centre for Cloud In Situ Measurements

Although it is not an obligation, the Centre for Cloud In Situ Measurements should work to sustain a high
level of performance and to stimulate the advancement of new techniques and methodologies for
measuring cloud variables and INPs in the atmosphere by:

* Development of strategies to increase the duty cycle of instruments operated at the NFs, to reduce breakdown and maintenance downtime;

* Development of new technological products and methods;

* Development of retrieval algorithms or tools for producing level 1 to 3 data, including the exploitation of instrument synergies;

* Organizing regular events (at least once every 2 years) and other forums, in order to exchange knowledge with the NFs and other scientists;

* Contributing to CEN, ISO, or similar standardization activities.
## 8.2.2 Technical obligations in relation with the ACTRIS Data Centre

The following general share of responsibilities between the Centre for Aerosol Remote Sensing and the ACTRIS Data Centre applies:

<table><thead><tr><td>Responsibilities at CIS</td><td>Responsibilities at ACTRIS DC</td></tr></thead><tbody><tr><td>The Centre for Aerosol Remote Sensing is responsible for developing and facilitating the implementation of the QA/QC procedures and tools at the ACTRIS NFs operating cloud in situ instruments, INP instruments and offline chemical analytics, in order to allow the respective NFs to keep control on the quality of their measurements (level 0 data)</td><td>ACTRIS Data Centre is responsible for the QC of the ACTRIS data produced from the respective measurements (level 1 to level 3 data), which are made available through the ACTRIS data portal</td></tr><tr><td>The Centre for Aerosol Remote Sensing is responsible for auditing the ACTRIS NFs operating cloud in situ instruments, INP instruments and offline chemical analytics, documenting the quality of the measurements, and providing all results to the ACTRIS Data Centre, in order to allow the traceability of the ACTRIS data which are made available through the ACTRIS data portal</td><td>ACTRIS Data Centre is responsible for the traceability and full documentation of the data quality of the ACTRIS data produced cloud in situ instruments, INP instruments and offline chemical analytics, which are made available through the ACTRIS data portal. Results of quality assurance procedures applied by the Centre for Cloud In Situ Measurements will be traced into the data products.</td></tr><tr><td>The Centre for Aerosol Remote Sensing is responsible for developing and testing new retrieval algorithms or tools for producing level 1 to 3 data, including the exploitation of instrument synergies</td><td>ACTRIS Data Centre is responsible for implementing the approved retrieval algorithms or tools into the ACTRIS Data Centre operation</td></tr></tbody></table>

The workflow between the ACTRIS NFs, the Centre for Cloud In Situ Measurements and the ACTRIS Data Centre is as follows:

* CIS develops and provides QA/QC procedures

* ACTRIS NF implements and applies QA/QC procedures and participates in audits

* ACTRIS NF delivers level 0 data to the DC for archiving and to CIS for quality control and approval

* The NF creates level 1 and level 2 data according to procedures implemented and approved by CIS and send these data to the data centre for archiving

* For variables with automatic quality control the DC will process the level 0 data.