# Deliverable D 9.2: Final report on access to advanced ACTRIS stations

Ariane Dubost, Sabine Philippin

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Ariane Dubost, Sabine Philippin. Deliverable D 9.2: Final report on access to advanced ACTRIS stations. CNRS. 2019. hal-04610594

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Submitted on 13 Jun 2024

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# Deliverable D 9.2: Final report on access to advanced ACTRIS stations

Ariane Dubost, Sabine Philippin

► To cite this version:

Ariane Dubost, Sabine Philippin. Deliverable D 9.2: Final report on access to advanced ACTRIS stations. CNRS. 2019. hal-04610594

HAL Id: hal-04610594

https://hal.science/hal-04610594v1

Submitted on 13 Jun 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
Deliverable D 9.2: Final report on access to advanced ACTRIS stations

TNA Access office : Ariane Dubost, Sabine Philippin (CNRS),

Access providers : Jean-Pierre Cammas, Martial Haeffelin, Karine, Sellegri (CNRS) Fabio Madonna, Lucia Mona, Angela Marioni (CNR), Tukka Petaja (UHEL), Heikki Lihavainen (FMI), Urs Baltensperger (PSI), Arnoud Apituley (KNMI), Gerald Spindler (TROPOS), Nikolaos Mihalopoulos (NOA), Vana Milan (CHMI), Emilio Cuevas (UVA), Lucas Alados (UGR), Andres Alastuey (CSIC), Erik Swietlicki (ULUND), Mihalis Vrekoussis (CAO), Colin Odowd (NUIG)

<table><tr><td>Work package no</td><td>WP9</td></tr><tr><td>Deliverable no.</td><td>D9.2</td></tr><tr><td>Lead beneficiary</td><td>CNRS</td></tr><tr><td>Deliverable type</td><td>☑ R (Document, report)<br/>☐ DEC (Websites, patent fillings, videos, etc.)<br/>☐ OTHER: please specify....................................</td></tr><tr><td>Dissemination level</td><td>☑ PU (public)<br/>☐ CO (confidential, only for members of the Consortium, incl Commission)</td></tr><tr><td>Estimated delivery date</td><td>Month 48</td></tr><tr><td>Actual delivery date</td><td>08/2019</td></tr><tr><td>Version</td><td>2</td></tr><tr><td>Comments</td><td>This document acts as an update to the Intermediate Report on access to advanced ACTRIS stations (D9.1) submitted on M24.<br/>As some TNA projects ended in April 2019, finalization and submission of the deliverable was delayed to enable inclusion of all information.</td></tr></table>
Deliverable D 9.2: Final report on access to advanced ACTRIS stations

TNA Access office : Ariane Dubost, Sabine Philippin (CNRS),

Access providers : Jean-Pierre Cammas, Martial Haeffelin, Karine, Sellegrì (CNRS) Fabio Madonna, Lucia Mona, Angela Marioni (CNR), Tukka Petaja (UHEL), Heikki Lihavainen (FMI), Urs Baltensperger (PSI), Arnoud Apituley (KNMI), Gerald Spindler (TROPOS), Nikolaos Mihalopoulos (NOA), Vana Milan (CHMI), Emilio Cuevas (UVA), Lucas Alados (UGR), Andres Alastuey (CSIC), Erik Swietlicki (ULUND), Mihalis Vrekoussis (CAO), Colin Odowd (NUIG)

<table><tr><td>Work package no</td><td>WP9</td></tr><tr><td>Deliverable no.</td><td>D9.2</td></tr><tr><td>Lead beneficiary</td><td>CNRS</td></tr><tr><td>Deliverable type</td><td>☑ R (Document, report)<br/>☐ DEC (Websites, patent fillings, videos, etc.)<br/>☐ OTHER: please specify....................................</td></tr><tr><td>Dissemination level</td><td>☑ PU (public)<br/>☐ CO (confidential, only for members of the Consortium, incl Commission)</td></tr><tr><td>Estimated delivery date</td><td>Month 48</td></tr><tr><td>Actual delivery date</td><td>08/2019</td></tr><tr><td>Version</td><td>2</td></tr><tr><td>Comments</td><td>This document acts as an update to the Intermediate Report on access to advanced ACTRIS stations (D9.1) submitted on M24.<br/>As some TNA projects ended in April 2019, finalization and submission of the deliverable was delayed to enable inclusion of all information.</td></tr></table>
Table of Content

<table><tr><td>1</td><td>Introduction</td><td>4</td></tr><tr><td>2</td><td>Infrastructures providing Transnational access to advanced ACTRIS stations</td><td>4</td></tr><tr><td>3</td><td>Description of the transnational access procedure</td><td>5</td></tr><tr><td>3.1</td><td>Description of the publicity concerning the opportunities for access</td><td>5</td></tr><tr><td>3.1.1</td><td>Continuous calls for access via website and TNA infrastructure websites</td><td>5</td></tr><tr><td>3.1.2</td><td>Special calls for access</td><td>5</td></tr><tr><td>3.1.3</td><td>Mailing lists and electronic means</td><td>7</td></tr><tr><td>3.1.4</td><td>Outreach activities</td><td>8</td></tr><tr><td>3.1.5</td><td>Newsletters, brochures, and other outreach material</td><td>9</td></tr><tr><td>3.2</td><td>Description of the selection procedure</td><td>10</td></tr><tr><td>4</td><td>Summary of Transnational Access activity to advanced ACTRIS stations</td><td>10</td></tr><tr><td>5</td><td>Description of Transnational Access</td><td>18</td></tr><tr><td>5.1</td><td>CNR IMAA Atmospheric Observatory, CIAO (CNR)</td><td>19</td></tr><tr><td>5.2</td><td>Monte Cimone taking advantage of Po Valley facility, CMN (CNR)</td><td>21</td></tr><tr><td>5.3</td><td>SIRTA Atmospheric Research Observatory, SIR (CNRS)</td><td>22</td></tr><tr><td>5.4</td><td>Puy de Dôme Observatory, PUY (CNRS, UBP)</td><td>24</td></tr><tr><td>5.5</td><td>Maïdo Observatory - Observatoire de Physique de l'Atmosphère à La Réunion, MAIDO-OPAR (CNRS, UR)</td><td>26</td></tr><tr><td>5.6</td><td>Station for Measuring Ecosystem - Atmosphere Relations II, SMR (UHEL)</td><td>28</td></tr><tr><td>5.7</td><td>Pallas-Sodankylä Global Atmospheric Watch Station, PAL (FMI)</td><td>30</td></tr><tr><td>5.8</td><td>High Altitude Research Station Jungfraujoch, JFJ (PSI)</td><td>31</td></tr><tr><td>5.9</td><td>Cabauw Experimental Site for Atmospheric Research, CESAR (KNMI, TNO, TUD, UU, ECN)</td><td>34</td></tr><tr><td>5.10</td><td>TROPOS Research Station Melpitz, MEL (TROPOS)</td><td>35</td></tr><tr><td>5.11</td><td>Finokalia Atmospheric Observatory, FKL (NOA)</td><td>36</td></tr></table>
Table of Content

<table><tr><td>1</td><td>Introduction</td><td>4</td></tr><tr><td>2</td><td>Infrastructures providing Transnational access to advanced ACTRIS stations</td><td>4</td></tr><tr><td>3</td><td>Description of the transnational access procedure</td><td>5</td></tr><tr><td>3.1</td><td>Description of the publicity concerning the opportunities for access</td><td>5</td></tr><tr><td>3.1.1</td><td>Continuous calls for access via website and TNA infrastructure websites</td><td>5</td></tr><tr><td>3.1.2</td><td>Special calls for access</td><td>5</td></tr><tr><td>3.1.3</td><td>Mailing lists and electronic means</td><td>7</td></tr><tr><td>3.1.4</td><td>Outreach activities</td><td>8</td></tr><tr><td>3.1.5</td><td>Newsletters, brochures, and other outreach material</td><td>9</td></tr><tr><td>3.2</td><td>Description of the selection procedure</td><td>10</td></tr><tr><td>4</td><td>Summary of Transnational Access activity to advanced ACTRIS stations</td><td>10</td></tr><tr><td>5</td><td>Description of Transnational Access</td><td>18</td></tr><tr><td>5.1</td><td>CNR IMAA Atmospheric Observatory, CIAO (CNR)</td><td>19</td></tr><tr><td>5.2</td><td>Monte Cimone taking advantage of Po Valley facility, CMN (CNR)</td><td>21</td></tr><tr><td>5.3</td><td>SIRTA Atmospheric Research Observatory, SIR (CNRS)</td><td>22</td></tr><tr><td>5.4</td><td>Puy de Dôme Observatory, PUY (CNRS, UBP)</td><td>24</td></tr><tr><td>5.5</td><td>Maïdo Observatory - Observatoire de Physique de l'Atmosphère à La Réunion, MAIDO-OPAR (CNRS, UR)</td><td>26</td></tr><tr><td>5.6</td><td>Station for Measuring Ecosystem - Atmosphere Relations II, SMR (UHEL)</td><td>28</td></tr><tr><td>5.7</td><td>Pallas-Sodankylä Global Atmospheric Watch Station, PAL (FMI)</td><td>30</td></tr><tr><td>5.8</td><td>High Altitude Research Station Jungfraujoch, JFJ (PSI)</td><td>31</td></tr><tr><td>5.9</td><td>Cabauw Experimental Site for Atmospheric Research, CESAR (KNMI, TNO, TUD, UU, ECN)</td><td>34</td></tr><tr><td>5.10</td><td>TROPOS Research Station Melpitz, MEL (TROPOS)</td><td>35</td></tr><tr><td>5.11</td><td>Finokalia Atmospheric Observatory, FKL (NOA)</td><td>36</td></tr></table>
<table><tr><td>5.12 Košetice-Křešín u Pacova, KOS (CHMI, ICPF, CVGZ)</td><td>37</td></tr><tr><td>5.13 Izana Subtropical Access Facility, ISAF (AEMET)</td><td>41</td></tr><tr><td>5.14 Granada Atmospheric Observatory, GRA (UGR)</td><td>43</td></tr><tr><td>5.15 CSIC Montseny, MSY (CSIC)</td><td>45</td></tr><tr><td>5.16 Hyltemossa, HYM (ULUND)</td><td>47</td></tr><tr><td>5.17 Cyprus Atmospheric Observatory, CAO (CYI)</td><td>47</td></tr><tr><td>5.18 Mace Head Research Station, MHD (NUIG)</td><td>48</td></tr><tr><td>6 Publications and output and resulting from Transnational Access to advanced ACTRIS stations</td><td>50</td></tr><tr><td>Appendix A: Document templates used within the process of TNA to observation facilities – Application form</td><td>57</td></tr><tr><td>Appendix B: Document templates used within the process of TNA to observation facilities – Review form</td><td>64</td></tr><tr><td>Appendix C: Document templates used within the process of TNA to observation facilities – Confirmation of Access</td><td>66</td></tr><tr><td>Appendix D: Document templates used within the process of TNA to observation facilities – Scientific activity report</td><td>67</td></tr></table>
<table><tr><td>5.12 Košetice-Křešín u Pacova, KOS (CHMI, ICPF, CVGZ)</td><td>37</td></tr><tr><td>5.13 Izana Subtropical Access Facility, ISAF (AEMET)</td><td>41</td></tr><tr><td>5.14 Granada Atmospheric Observatory, GRA (UGR)</td><td>43</td></tr><tr><td>5.15 CSIC Montseny, MSY (CSIC)</td><td>45</td></tr><tr><td>5.16 Hyltemossa, HYM (ULUND)</td><td>47</td></tr><tr><td>5.17 Cyprus Atmospheric Observatory, CAO (CYI)</td><td>47</td></tr><tr><td>5.18 Mace Head Research Station, MHD (NUIG)</td><td>48</td></tr><tr><td>6 Publications and output and resulting from Transnational Access to advanced ACTRIS stations</td><td>50</td></tr><tr><td>Appendix A: Document templates used within the process of TNA to observation facilities – Application form</td><td>57</td></tr><tr><td>Appendix B: Document templates used within the process of TNA to observation facilities – Review form</td><td>64</td></tr><tr><td>Appendix C: Document templates used within the process of TNA to observation facilities – Confirmation of Access</td><td>66</td></tr><tr><td>Appendix D: Document templates used within the process of TNA to observation facilities – Scientific activity report</td><td>67</td></tr></table>
# Final report on access to advanced ACTRIS stations

## 1 Introduction

ACTRIS-2 provided a coordinated framework to support and facilitate physical access to a selected number of advanced ACTRIS stations in Europe to a wide community of users. The objective of this document is to report in details on the outcome of the Transnational Access activity to observational facilities for the entire project.

## 2 Infrastructures providing Transnational access to advanced ACTRIS stations

Within work package 9, ACTRIS-2 has provided physical, free-of-charge, transnational access (TNA) to users from the academic and private sector to 18 observational facilities in Europe. The ACTRIS stations offering TNA are advanced multi-instrumented facilities for atmospheric observations and are unique within Europe. The facilities were selected for their representative location (with respect to air mass type, altitude etc.), most of them have been operational for decades (except for a few new stations), documenting a long record and experience of access with available logistics to accommodate external research groups, and offer high quality research equipment making them world-class research stations. An overview of the observational facilities offering TNA is given in Figure 1, a short description of the infrastructures is provided on the ACTRIS website at: http://www.actris.eu/DataServices/ObservationalFacilities/AccesstoObservationalFacilities.aspx

<figure><img src="image_2.png" /><figcaption>Figure 1: Overview of observational facilities within ACTRIS-2 providing physical TNA.</figcaption></figure>

The observational facilities comprise high altitude research stations, e.g., PUY (1565 m, regional background), MAIDO (2160 m, south-western, tropical Indian Ocean), CMN (2165 m, polluted environment), ISAF (2370 m, subtropical site, free troposphere), JFJ (3500 m, free troposphere), stations in Northern Europe's boreal forest (SMR, HYM, PAL at border of
# Final report on access to advanced ACTRIS stations

## 1 Introduction

ACTRIS-2 provided a coordinated framework to support and facilitate physical access to a selected number of advanced ACTRIS stations in Europe to a wide community of users. The objective of this document is to report in details on the outcome of the Transnational Access activity to observational facilities for the entire project.

## 2 Infrastructures providing Transnational access to advanced ACTRIS stations

Within work package 9, ACTRIS-2 has provided physical, free-of-charge, transnational access (TNA) to users from the academic and private sector to 18 observational facilities in Europe. The ACTRIS stations offering TNA are advanced multi-instrumented facilities for atmospheric observations and are unique within Europe. The facilities were selected for their representative location (with respect to air mass type, altitude etc.), most of them have been operational for decades (except for a few new stations), documenting a long record and experience of access with available logistics to accommodate external research groups, and offer high quality research equipment making them world-class research stations. An overview of the observational facilities offering TNA is given in Figure 1, a short description of the infrastructures is provided on the ACTRIS website at: http://www.actris.eu/DataServices/ObservationalFacilities/AccesstoObservationalFacilities.aspx

<figure><img src="image_2.png" /><figcaption>Figure 1: Overview of observational facilities within ACTRIS-2 providing physical TNA.</figcaption></figure>

The observational facilities comprise high altitude research stations, e.g., PUY (1565 m, regional background), MAIDO (2160 m, south-western, tropical Indian Ocean), CMN (2165 m, polluted environment), ISAF (2370 m, subtropical site, free troposphere), JFJ (3500 m, free troposphere), stations in Northern Europe's boreal forest (SMR, HYM, PAL at border of
Arctic), maritime/continental stations (MHD, CESAR / SIR, MEL, KOS), Mediterranean stations with urban background (MSY, GRA, CIAO, FKL, CAO).

The opportunities for physical access have allowed external users, including those from the private sector and users from outside Europe, to have access i) to cutting-edge research opportunities and ii) to intercomparison campaigns and for instrument testing using the state-of-the-art equipment for aerosol and cloud profiles, aerosol-cloud observations, and near-surface aerosol and trace gas observations, fostering research at the forefront of science; iii) to international capacity building opportunities by participating in scientific measurement campaigns and comprehensive measurement programmes, and by benefitting from the scientific expertise and support provided by the personnel operating the infrastructures, and from the available high level of services, including training to young scientists and new users.

## 3 Description of the transnational access procedure

The TNA activity to observational facilities offered within ACTRIS-2 has been based on specific guidelines and rules for access that follow the Horizon 2020 rules. The procedure is described below, including the advertisement of the opportunities for access and the specific procedure of proposal submission, evaluation, and selection.

### 3.1 Description of the publicity concerning the opportunities for access

A number of measures have been taken to advertise the opportunities of transnational access within ACTRIS-2:

#### 3.1.1 Continuous calls for access via website and TNA infrastructure websites

An official permanent call concerning transnational access opportunities to the observational facilities within WP9 was largely publicized at project start via the ACTRIS-2 website and simultaneously permanently promoted via the websites of the observational facilities and related projects/networks concerned. Please refer to D9.1 for more details (available at the ACTRIS website).

#### 3.1.2 Special calls for access

A number of special calls to the calibration and observational facilities were launched and widely announced throughout the project. The measurement campaigns and related activities have pursued defined objectives for calibration and intercomparison exercises, measurement campaigns, or joint TNA opportunities with collaborating EU-Integrating activities. These were organized either by the corresponding access providers and/or were linked with ACTRIS-2 networking and joint research activities if carried out at an infrastructure open for TNA, and allowed other research groups outside the project to participate via the TNA opportunities. An overview of corresponding TNA opportunities organized throughout the length of the project is listed in Table 1.
Arctic), maritime/continental stations (MHD, CESAR / SIR, MEL, KOS), Mediterranean stations with urban background (MSY, GRA, CIAO, FKL, CAO).

The opportunities for physical access have allowed external users, including those from the private sector and users from outside Europe, to have access i) to cutting-edge research opportunities and ii) to intercomparison campaigns and for instrument testing using the state-of-the-art equipment for aerosol and cloud profiles, aerosol-cloud observations, and near-surface aerosol and trace gas observations, fostering research at the forefront of science; iii) to international capacity building opportunities by participating in scientific measurement campaigns and comprehensive measurement programmes, and by benefitting from the scientific expertise and support provided by the personnel operating the infrastructures, and from the available high level of services, including training to young scientists and new users.

## 3 Description of the transnational access procedure

The TNA activity to observational facilities offered within ACTRIS-2 has been based on specific guidelines and rules for access that follow the Horizon 2020 rules. The procedure is described below, including the advertisement of the opportunities for access and the specific procedure of proposal submission, evaluation, and selection.

### 3.1 Description of the publicity concerning the opportunities for access

A number of measures have been taken to advertise the opportunities of transnational access within ACTRIS-2:

#### 3.1.1 Continuous calls for access via website and TNA infrastructure websites

An official permanent call concerning transnational access opportunities to the observational facilities within WP9 was largely publicized at project start via the ACTRIS-2 website and simultaneously permanently promoted via the websites of the observational facilities and related projects/networks concerned. Please refer to D9.1 for more details (available at the ACTRIS website).

#### 3.1.2 Special calls for access

A number of special calls to the calibration and observational facilities were launched and widely announced throughout the project. The measurement campaigns and related activities have pursued defined objectives for calibration and intercomparison exercises, measurement campaigns, or joint TNA opportunities with collaborating EU-Integrating activities. These were organized either by the corresponding access providers and/or were linked with ACTRIS-2 networking and joint research activities if carried out at an infrastructure open for TNA, and allowed other research groups outside the project to participate via the TNA opportunities. An overview of corresponding TNA opportunities organized throughout the length of the project is listed in Table 1.
<table><caption>Table 1: Special calls to transnational access opportunities launched since project start</caption><thead><tr><td>TNA Opportunity</td><td>Dates</td><td>Organizer / Access provider / Location</td><td>Website address</td></tr></thead><tbody><tr><td>MelCol 2015</td><td>June 2015</td><td>TROPOS / MEL Germany</td><td>http://www.actris.eu/Outreach/News/Campaigns/Melpitzcolu mn2015.aspx</td></tr><tr><td>PACE 2015</td><td>September- December 2015</td><td>FMI / PAL Finland</td><td>http://www.actris.eu/Events/Ca mpaigns/PACE2015.aspx</td></tr><tr><td>Athens Smog Campaign</td><td>December 2015- February 2016</td><td>NOA / FKL Greece</td><td>http://www.actris.eu/Outreach/ News/Campaigns/JRA1Athens Dec2015.aspx</td></tr><tr><td>Cyprus campaign 2016</td><td>April 2016</td><td>CYI, CAO Cyprus</td><td>http://www.actris.eu/Outreach/ News/Campaigns/Cyprus2016. aspx</td></tr><tr><td>INTERACT II</td><td>July-December 2016</td><td>CNR-IMAA / CIAO Italy</td><td>http://www.actris.eu/Outreach/ News/Campaigns/INTERACT IICampaign2016.aspx</td></tr><tr><td>Precipitation Field Campaign 2016</td><td>September- December 2016</td><td>CNRS / SIRTA France</td><td>http://www.actris.eu/Portals/46 /Outreach/Campaigns/SIRTA- TNA_precipitation_2016.pdf? ver=2016-07-19-175127-140</td></tr><tr><td>Intercomparison Field campaign at PUY</td><td>October 2016</td><td>CNRS / PUY France</td><td>http://www.actris.eu/Outreach/ News/Campaigns/Intercompari sonfieldcampaign2016.aspx</td></tr><tr><td>ACTRIS-2 &amp; EUFAR TNA</td><td>2016-2017</td><td></td><td>http://www.actris.eu/Outreach/ News/CallsforTNA/CallforAC TRIS-2EUFARjointTNA.aspx</td></tr><tr><td>CyCARE Campaign 2017</td><td>October 2016- August 2017</td><td>TROPOS/CYPRUS University of Technology</td><td>https://www.tropos.de/en/instit ute/departments/remote- sensing-of-atmospheric- processes-new/ground-based- remote-sensing/cyprus-clouds- aerosol-and-rain-experiment cycare/</td></tr><tr><td>KOS Call for TNA</td><td>June 2017</td><td>National atmospheric observatory Košetice</td><td>https://www.actris.eu/Portals/4 6/Events/Events%20descriptio ns/2017/ACTRIS- 2%20(use%20precise%20folde r)/Flux_measurement%20cam paign_NAOK.pdf?ver=2017- 06-12-155852-737</td></tr><tr><td>PTR-MS Intercomparison</td><td>September 2017</td><td>Cabauw The Netherlands</td><td>http://www.actris.eu/Portals/46 /Events/Events%20description s/2017/PTR- MS%20campaign%20sept%20 2017/PTR.pdf?ver=2017-04- 03-134820-307</td></tr><tr><td>Cloud Radar Calibration Campaign</td><td>May 2018</td><td>SIRTA Observatory, France</td><td>http://www.actris.eu/Events/Ca mpaigns/CloudRadarCalibratio nCampaign,SIRTAObservator y2018.aspx</td></tr><tr><td>Aerosol Ice Nucleation Campaign</td><td>October 2018</td><td>PUY Station, France</td><td>https://www.actris.eu/Portals/4 6/Events/Events%20descriptio ns/2017/ACTRIS-</td></tr></tbody></table>
<table><caption>Table 1: Special calls to transnational access opportunities launched since project start</caption><thead><tr><td>TNA Opportunity</td><td>Dates</td><td>Organizer / Access provider / Location</td><td>Website address</td></tr></thead><tbody><tr><td>MelCol 2015</td><td>June 2015</td><td>TROPOS / MEL Germany</td><td>http://www.actris.eu/Outreach/News/Campaigns/Melpitzcolu mn2015.aspx</td></tr><tr><td>PACE 2015</td><td>September- December 2015</td><td>FMI / PAL Finland</td><td>http://www.actris.eu/Events/Ca mpaigns/PACE2015.aspx</td></tr><tr><td>Athens Smog Campaign</td><td>December 2015- February 2016</td><td>NOA / FKL Greece</td><td>http://www.actris.eu/Outreach/ News/Campaigns/JRA1Athens Dec2015.aspx</td></tr><tr><td>Cyprus campaign 2016</td><td>April 2016</td><td>CYI, CAO Cyprus</td><td>http://www.actris.eu/Outreach/ News/Campaigns/Cyprus2016. aspx</td></tr><tr><td>INTERACT II</td><td>July-December 2016</td><td>CNR-IMAA / CIAO Italy</td><td>http://www.actris.eu/Outreach/ News/Campaigns/INTERACT IICampaign2016.aspx</td></tr><tr><td>Precipitation Field Campaign 2016</td><td>September- December 2016</td><td>CNRS / SIRTA France</td><td>http://www.actris.eu/Portals/46 /Outreach/Campaigns/SIRTA- TNA_precipitation_2016.pdf? ver=2016-07-19-175127-140</td></tr><tr><td>Intercomparison Field campaign at PUY</td><td>October 2016</td><td>CNRS / PUY France</td><td>http://www.actris.eu/Outreach/ News/Campaigns/Intercompari sonfieldcampaign2016.aspx</td></tr><tr><td>ACTRIS-2 &amp; EUFAR TNA</td><td>2016-2017</td><td></td><td>http://www.actris.eu/Outreach/ News/CallsforTNA/CallforAC TRIS-2EUFARjointTNA.aspx</td></tr><tr><td>CyCARE Campaign 2017</td><td>October 2016- August 2017</td><td>TROPOS/CYPRUS University of Technology</td><td>https://www.tropos.de/en/instit ute/departments/remote- sensing-of-atmospheric- processes-new/ground-based- remote-sensing/cyprus-clouds- aerosol-and-rain-experiment cycare/</td></tr><tr><td>KOS Call for TNA</td><td>June 2017</td><td>National atmospheric observatory Košetice</td><td>https://www.actris.eu/Portals/4 6/Events/Events%20descriptio ns/2017/ACTRIS- 2%20(use%20precise%20folde r)/Flux_measurement%20cam paign_NAOK.pdf?ver=2017- 06-12-155852-737</td></tr><tr><td>PTR-MS Intercomparison</td><td>September 2017</td><td>Cabauw The Netherlands</td><td>http://www.actris.eu/Portals/46 /Events/Events%20description s/2017/PTR- MS%20campaign%20sept%20 2017/PTR.pdf?ver=2017-04- 03-134820-307</td></tr><tr><td>Cloud Radar Calibration Campaign</td><td>May 2018</td><td>SIRTA Observatory, France</td><td>http://www.actris.eu/Events/Ca mpaigns/CloudRadarCalibratio nCampaign,SIRTAObservator y2018.aspx</td></tr><tr><td>Aerosol Ice Nucleation Campaign</td><td>October 2018</td><td>PUY Station, France</td><td>https://www.actris.eu/Portals/4 6/Events/Events%20descriptio ns/2017/ACTRIS-</td></tr></tbody></table>
<table><thead><tr><td>TNA Opportunity</td><td>Dates</td><td>Organizer / Access provider / Location</td><td>Website address</td></tr></thead><tbody><tr><td></td><td></td><td></td><td>2%20(use%20precise%20folde r)/WP9/TNA_LaMP_Aerosol %20Ice%20nucleation%20Ca mpaign-2.pdf?ver=2017-11- 15-143627-383</td></tr><tr><td>SCC summer school</td><td>4-6 Dec. 2018</td><td>CIAO, Potenza, Italy</td><td>http://www.actris.eu/Events/Ev entsdescriptions/ACTRIS- 2Events/WP2SCCWinterScho ol.aspx</td></tr></tbody></table>

### 3.1.3 Mailing lists and electronic means

The launch of TNA opportunities and permanent and special calls for access to observational facilities were advertised via various mailing lists within the project but also outside ACTRIS-2, e.g., mailing lists of international networks and coordinated observations, projects, and cooperating scientific communities: ENVRIplus (Implementation and operation of cross-cutting services and solutions for clusters of ESFRI and other relevant research infrastructure initiatives, EU H2020), EUFAR (European Facility for Airborne Research, EU FP5,6,7), ESA (European Space Agency), ChArMEx (Chemistry-Aerosol-Mediterranean Experiment), INUIT (Ice Nuclei Research Unit). Furthermore used are the mailing lists of the more than 20 beneficiaries and linked third parties hosting TNA infrastructures, the mailing lists of national ACTRIS communities within Europe, and communication through direct links with international collaborators.
<table><thead><tr><td>TNA Opportunity</td><td>Dates</td><td>Organizer / Access provider / Location</td><td>Website address</td></tr></thead><tbody><tr><td></td><td></td><td></td><td>2%20(use%20precise%20folde r)/WP9/TNA_LaMP_Aerosol %20Ice%20nucleation%20Ca mpaign-2.pdf?ver=2017-11- 15-143627-383</td></tr><tr><td>SCC summer school</td><td>4-6 Dec. 2018</td><td>CIAO, Potenza, Italy</td><td>http://www.actris.eu/Events/Ev entsdescriptions/ACTRIS- 2Events/WP2SCCWinterScho ol.aspx</td></tr></tbody></table>

### 3.1.3 Mailing lists and electronic means

The launch of TNA opportunities and permanent and special calls for access to observational facilities were advertised via various mailing lists within the project but also outside ACTRIS-2, e.g., mailing lists of international networks and coordinated observations, projects, and cooperating scientific communities: ENVRIplus (Implementation and operation of cross-cutting services and solutions for clusters of ESFRI and other relevant research infrastructure initiatives, EU H2020), EUFAR (European Facility for Airborne Research, EU FP5,6,7), ESA (European Space Agency), ChArMEx (Chemistry-Aerosol-Mediterranean Experiment), INUIT (Ice Nuclei Research Unit). Furthermore used are the mailing lists of the more than 20 beneficiaries and linked third parties hosting TNA infrastructures, the mailing lists of national ACTRIS communities within Europe, and communication through direct links with international collaborators.
### 3.1.4 Outreach activities

The ACTRIS-2 infrastructures offering TNA have been largely promoted during invited talks, conferences (presentations and posters), workshops, project meetings, communications and direct announcements. Project brochures have been distributed at such events. Direct oral advertisement has proven efficient to encourage scientific activities at, e.g., TNA stations. See also Figures 2a-c).

<figure><img src="image_3.png" /><figcaption>Figure 2a: ACTRIS-2 poster advertising the access opportunities via TNA (EAC-2016)</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>Figure 2b: Advertisement for TNA infrastructure at Jungfraujoch, Switzerland (WP9).</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Figure 2c: Advertisement for TNA to observational facilities (2nd ACTRIS-2 Science meeting, Granada).</figcaption></figure>
### 3.1.4 Outreach activities

The ACTRIS-2 infrastructures offering TNA have been largely promoted during invited talks, conferences (presentations and posters), workshops, project meetings, communications and direct announcements. Project brochures have been distributed at such events. Direct oral advertisement has proven efficient to encourage scientific activities at, e.g., TNA stations. See also Figures 2a-c).

<figure><img src="image_3.png" /><figcaption>Figure 2a: ACTRIS-2 poster advertising the access opportunities via TNA (EAC-2016)</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>Figure 2b: Advertisement for TNA infrastructure at Jungfraujoch, Switzerland (WP9).</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Figure 2c: Advertisement for TNA to observational facilities (2nd ACTRIS-2 Science meeting, Granada).</figcaption></figure>
### 3.1.5 Newsletters, brochures, and other outreach material

TNA infrastructure and services is also advertised through further promotional channels such as posters, brochures, and leaflets (Figures 3a-c), distributed at conferences or meetings or by e-mail.

<figure><img src="image_6.png" /><figcaption>Figure 3a: ACTRIS-2 project brochure promoting the access opportunities via TNA (WP1).</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Figure 3b: Leaflet offering Transnational Access to the infrastructure Košetice – Křešín u Pacova (WP9 / KPO), July 2015.</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>Figure 3c: Leaflet about description of opportunities at the Atmospheric research facility at Agia Marina Xiliatou (WP9 / CAO), June 2016.</figcaption></figure>

Social medias were also used to promote TNA opportunities as for instance ACTRIS twitter channel (@ACTRISRI) with about 5000 reach:

<figure><img src="image_9.png" /><figcaption>Figure 3d: ACTRIS Twitter account promoting the access opportunities via TNA.</figcaption></figure>
### 3.1.5 Newsletters, brochures, and other outreach material

TNA infrastructure and services is also advertised through further promotional channels such as posters, brochures, and leaflets (Figures 3a-c), distributed at conferences or meetings or by e-mail.

<figure><img src="image_6.png" /><figcaption>Figure 3a: ACTRIS-2 project brochure promoting the access opportunities via TNA (WP1).</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Figure 3b: Leaflet offering Transnational Access to the infrastructure Košetice – Křešín u Pacova (WP9 / KPO), July 2015.</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>Figure 3c: Leaflet about description of opportunities at the Atmospheric research facility at Agia Marina Xiliatou (WP9 / CAO), June 2016.</figcaption></figure>

Social medias were also used to promote TNA opportunities as for instance ACTRIS twitter channel (@ACTRISRI) with about 5000 reach:

<figure><img src="image_9.png" /><figcaption>Figure 3d: ACTRIS Twitter account promoting the access opportunities via TNA.</figcaption></figure>
## 3.2 Description of the selection procedure

The centralised access and application procedure is described in details in D9.1 "Intermediate Report on access to advanced ACTRIS stations" which is available at the ACTRIS website.

# 4 Summary of Transnational Access activity to advanced ACTRIS stations

The call for physical access was launched in the beginning of the project. Since the start of the project, 153 proposals to the 18 observational facilities have been received of which 136 were selected for access support. 6 proposals were withdrawn by the users, 6 were not eligible and 5 more were not evaluated sufficiently high to reach the threshold to be accepted. The quantity of access provided (referring to estimated access and ongoing projects) in units of RWD (1 research-person-working-day) since the beginning of the project equals to 3'202 days corresponding to 145% out of the estimated access of 2'195 days foreseen in the contract. This is a positive figure showing that access has continued even after the travel ands subsistance budget have been spent.

## International collaboration

The importance and impact of access opportunities offered by ACTRIS-2 world-wide is clearly demonstrated. Since the start of the project 605 access days have been consumed by users outside Europe (19%), slightly below the threshold for the overall limit of 20% (WP9 TNA only). This corresponds to 26 projects (see figure 5 below).

Those international users came from 18 different countries: Algeria, Antigua and Barbuda, Argentina, Brazil, Canada, Chile, China, Colombia, Costa Rica, Indonesia, Mexico, Nigeria, Russia, South Korea, United States, Taiwan, Tunisia, Turkey.

<figure><img src="image_10.png" /><figcaption>Figure 5: Breakdown of physical TNA user projects originating from countries within and outside EU, during the ACTRIS-2 project.</figcaption></figure>
## 3.2 Description of the selection procedure

The centralised access and application procedure is described in details in D9.1 "Intermediate Report on access to advanced ACTRIS stations" which is available at the ACTRIS website.

# 4 Summary of Transnational Access activity to advanced ACTRIS stations

The call for physical access was launched in the beginning of the project. Since the start of the project, 153 proposals to the 18 observational facilities have been received of which 136 were selected for access support. 6 proposals were withdrawn by the users, 6 were not eligible and 5 more were not evaluated sufficiently high to reach the threshold to be accepted. The quantity of access provided (referring to estimated access and ongoing projects) in units of RWD (1 research-person-working-day) since the beginning of the project equals to 3'202 days corresponding to 145% out of the estimated access of 2'195 days foreseen in the contract. This is a positive figure showing that access has continued even after the travel ands subsistance budget have been spent.

## International collaboration

The importance and impact of access opportunities offered by ACTRIS-2 world-wide is clearly demonstrated. Since the start of the project 605 access days have been consumed by users outside Europe (19%), slightly below the threshold for the overall limit of 20% (WP9 TNA only). This corresponds to 26 projects (see figure 5 below).

Those international users came from 18 different countries: Algeria, Antigua and Barbuda, Argentina, Brazil, Canada, Chile, China, Colombia, Costa Rica, Indonesia, Mexico, Nigeria, Russia, South Korea, United States, Taiwan, Tunisia, Turkey.

<figure><img src="image_10.png" /><figcaption>Figure 5: Breakdown of physical TNA user projects originating from countries within and outside EU, during the ACTRIS-2 project.</figcaption></figure>
## Private sector collaboration

Through TNA, ACTRIS-2 has strengthened its links and fostered participation with the private sector. 13 out of the total 136 TNA requests accepted involved the private sector -representing 89 access days and 10% of the projects carried out. In the 1st reporting period, SME requests were Envircontrol SA, Belgium. Under the second reporting period were Palas GmbH-Germany, Sunset Laboratory BV-The Netherlands, GRASP and Aerodyne Research Inc. In the third reporting period were Aerosol doo, Droplet Measurement technologies, EKO Instruments EUROPE BV, IONICON Analytik and Raymetrics SA. The milestone report MS4.5 details the SMEs access to ACTRIS-2 facilities.

The use of the ACTRIS observational platforms by the thirteen private sector users is shortly summarized in the following:

### Aerodyne Research Inc. (USA) @ Monte Cimone/Po Valley facility (CMN, Italy)

Aerodyne Research Inc. is an instrument manufacturer that provides instrumentation and consulting for environmental air quality monitoring and measurements. The Aerodyne Center for Sensor Systems and Technology (CSST) designs and develops innovative sensors utilizing proprietary technology for its own use and for delivery to private, academic and government customers. It has built and marketed state-of-the-art monitors that employ cavity attenuated phase shift (CAPS) techniques. One of such CAPS monitors is the CAPS SSA, a single scattering albedo monitor for direct, combined measurements of both extinction and scattering in the same volume. Particle absorption can be obtained by subtraction of the two measured quantities (extinction minus scattering), with an uncertainty of 5-6%. Upcoming in July 2017, Aerodyne participates in an international field campaign at the Monte Cimone and Po Valley sites to assess the accuracy of aerosol absorption and black carbon measurements. The CAPS SSA is collocated with other instrumentation for aerosol measurements of optical, physical, and chemical properties: a nephelometer, an Aerosol Chemical Speciation Monitor, an optical particle counter. The presence of multiple techniques for measuring aerosol absorption (by difference with the CAPS SSA and on a filter) will allow measurement intercomparison and observe the changes in optical properties with changes in the chemical composition of the sub-micron aerosol as determined by the ACSM. In particular, the specific goal of the campaign is a comprehensive closure between absorption coefficient and BC concentration and an assessment of the reasons for the variability of the mass absorption efficiency using commercial instrumentation.

### Aerodyne Research Inc. (USA) @ KNMI - Cabauw Experimental Site for Atmospheric Research (CESAR, The Netherlands)

AVVICATO (Application of a VOCUS VOC Integrated Calibration system at a Tower Observatory) involved the manufacturer Aerodyne Research Inc. using their automated PTR-MS calibration and background system in cooperation with other PTR instruments. The constructed PTR time-of-flight mass spectrometer (PTR-ToFMS) has a unique ionization source compared to other instruments in attendance, and has never been quantitatively evaluated against other PTR instruments.

### Aerosol d.o.o. (Slovenia) @ Cyprus Atmospheric Observatory (CAO, Cyprus)

Aerosol d.o.o is a SME that develops and manufactures Aethalometer® instruments that are used in air monitoring network stations for sampling and measurement of the mass
## Private sector collaboration

Through TNA, ACTRIS-2 has strengthened its links and fostered participation with the private sector. 13 out of the total 136 TNA requests accepted involved the private sector -representing 89 access days and 10% of the projects carried out. In the 1st reporting period, SME requests were Envircontrol SA, Belgium. Under the second reporting period were Palas GmbH-Germany, Sunset Laboratory BV-The Netherlands, GRASP and Aerodyne Research Inc. In the third reporting period were Aerosol doo, Droplet Measurement technologies, EKO Instruments EUROPE BV, IONICON Analytik and Raymetrics SA. The milestone report MS4.5 details the SMEs access to ACTRIS-2 facilities.

The use of the ACTRIS observational platforms by the thirteen private sector users is shortly summarized in the following:

### Aerodyne Research Inc. (USA) @ Monte Cimone/Po Valley facility (CMN, Italy)

Aerodyne Research Inc. is an instrument manufacturer that provides instrumentation and consulting for environmental air quality monitoring and measurements. The Aerodyne Center for Sensor Systems and Technology (CSST) designs and develops innovative sensors utilizing proprietary technology for its own use and for delivery to private, academic and government customers. It has built and marketed state-of-the-art monitors that employ cavity attenuated phase shift (CAPS) techniques. One of such CAPS monitors is the CAPS SSA, a single scattering albedo monitor for direct, combined measurements of both extinction and scattering in the same volume. Particle absorption can be obtained by subtraction of the two measured quantities (extinction minus scattering), with an uncertainty of 5-6%. Upcoming in July 2017, Aerodyne participates in an international field campaign at the Monte Cimone and Po Valley sites to assess the accuracy of aerosol absorption and black carbon measurements. The CAPS SSA is collocated with other instrumentation for aerosol measurements of optical, physical, and chemical properties: a nephelometer, an Aerosol Chemical Speciation Monitor, an optical particle counter. The presence of multiple techniques for measuring aerosol absorption (by difference with the CAPS SSA and on a filter) will allow measurement intercomparison and observe the changes in optical properties with changes in the chemical composition of the sub-micron aerosol as determined by the ACSM. In particular, the specific goal of the campaign is a comprehensive closure between absorption coefficient and BC concentration and an assessment of the reasons for the variability of the mass absorption efficiency using commercial instrumentation.

### Aerodyne Research Inc. (USA) @ KNMI - Cabauw Experimental Site for Atmospheric Research (CESAR, The Netherlands)

AVVICATO (Application of a VOCUS VOC Integrated Calibration system at a Tower Observatory) involved the manufacturer Aerodyne Research Inc. using their automated PTR-MS calibration and background system in cooperation with other PTR instruments. The constructed PTR time-of-flight mass spectrometer (PTR-ToFMS) has a unique ionization source compared to other instruments in attendance, and has never been quantitatively evaluated against other PTR instruments.

### Aerosol d.o.o. (Slovenia) @ Cyprus Atmospheric Observatory (CAO, Cyprus)

Aerosol d.o.o is a SME that develops and manufactures Aethalometer® instruments that are used in air monitoring network stations for sampling and measurement of the mass
concentration of black carbon particles. The SME supplied a platform, installed at CAO in
December 2018 in the frame of the CADB project led by Grisa Mocnik, from the J. Stefan
Institute, using Aethalometers AE33 with different inlets to:

* measure fine aerosol absorption (AE33 with a PM1 inlet),

* measure concentrated coarse fraction absorption (AE33 with a virtual impactor inlet and calculating the coarse fraction absorption as a difference between the concentrated sample (which contains some fine fraction) and the fine fraction. In addition to the measurements of absorbing aerosols, additional measurements of all carbonaceous aerosols at high time resolution have been implemented at Nicosia.

### Aerosol d.o.o. (Slovenia) @ CSIC Montseny (MSY, Spain)

This private company supplied a platform, installed at MSY in February 2019 in the frame of the CADB-2 project led by Grisa Mocnik, from the J. Stefan Institute, using Aethalometers AE33 with different inlets to measure fine aerosol absorption (AE33 with a PM1 inlet), and to measure concentrated coarse fraction absorption (AE33 with a virtual impactor inlet). Aerosol d.o.o has supplied two additional platforms installed at BCN urban background sites and MSC mountain site. This approach together with concurrent aircraft measurements will permit to determine the pure Saharan dust optical properties before it is mixed into the receptor site mixing layer, discriminating whether internally mixed dust and BC are from the source or receptor regions, respectively.

### Droplet measurement technologies, (USA) @ Puy de Dome high altitude station (PUY, France)

Droplet measurement technologies is an instrument manufacturer based in Colorado, USA, specialized in the production of cutting-edge instruments for measuring water droplets, ice crystals, CCN, black carbon, bioaerosols and other aerosols. The company provides accessories for these instruments such as calibration devices and power distribution systems, as well as high-quality software.

The company accessed the Puy de Dome high altitude station in France with a Spectrometer for Ice Nuclei (SPIN), which is one of the ice nuclei spectrometers commercially available. Given the wide variety of ice nucleation instruments in use, differences in ice nucleation observations arise, in part, from the different techniques used. The TNA project proposal aimed at describing the differences between one SPIN unit versus another, as well as to compare SPIN with other types of CFDCs. Understanding the source of these differences helps with data quality of SPIN in particular and CFDCs in general. Furthermore, an improved SPIN enables scientists interested in conducting measurement with access to an instrument that is well characterized by experts in this field. Specific objectives of the project have been i) the characterization of the differences in particle concentrations measured by SPIN units and other CFDCs under different meteorological conditions; ii) the characterization and investigation about features of the parallel plate type CFDC to better learn how to calibrate instruments of this type and in what detail the calibration is necessary; iii) the improvement of methods and procedures to minimize frost background in SPIN, isolating the effects that lead to frost formation and implementing changes in the procedure that might arise in frost; iv) improved measurement of ice crystal concentrations by utilizing advanced analysis techniques of particle-by-particle polarization ratio.

### EKO Instruments EUROPE BV (The Netherlands) @ Izaña Subtropical Access Facility (ISAF, Spain)
concentration of black carbon particles. The SME supplied a platform, installed at CAO in
December 2018 in the frame of the CADB project led by Grisa Mocnik, from the J. Stefan
Institute, using Aethalometers AE33 with different inlets to:

* measure fine aerosol absorption (AE33 with a PM1 inlet),

* measure concentrated coarse fraction absorption (AE33 with a virtual impactor inlet and calculating the coarse fraction absorption as a difference between the concentrated sample (which contains some fine fraction) and the fine fraction. In addition to the measurements of absorbing aerosols, additional measurements of all carbonaceous aerosols at high time resolution have been implemented at Nicosia.

### Aerosol d.o.o. (Slovenia) @ CSIC Montseny (MSY, Spain)

This private company supplied a platform, installed at MSY in February 2019 in the frame of the CADB-2 project led by Grisa Mocnik, from the J. Stefan Institute, using Aethalometers AE33 with different inlets to measure fine aerosol absorption (AE33 with a PM1 inlet), and to measure concentrated coarse fraction absorption (AE33 with a virtual impactor inlet). Aerosol d.o.o has supplied two additional platforms installed at BCN urban background sites and MSC mountain site. This approach together with concurrent aircraft measurements will permit to determine the pure Saharan dust optical properties before it is mixed into the receptor site mixing layer, discriminating whether internally mixed dust and BC are from the source or receptor regions, respectively.

### Droplet measurement technologies, (USA) @ Puy de Dome high altitude station (PUY, France)

Droplet measurement technologies is an instrument manufacturer based in Colorado, USA, specialized in the production of cutting-edge instruments for measuring water droplets, ice crystals, CCN, black carbon, bioaerosols and other aerosols. The company provides accessories for these instruments such as calibration devices and power distribution systems, as well as high-quality software.

The company accessed the Puy de Dome high altitude station in France with a Spectrometer for Ice Nuclei (SPIN), which is one of the ice nuclei spectrometers commercially available. Given the wide variety of ice nucleation instruments in use, differences in ice nucleation observations arise, in part, from the different techniques used. The TNA project proposal aimed at describing the differences between one SPIN unit versus another, as well as to compare SPIN with other types of CFDCs. Understanding the source of these differences helps with data quality of SPIN in particular and CFDCs in general. Furthermore, an improved SPIN enables scientists interested in conducting measurement with access to an instrument that is well characterized by experts in this field. Specific objectives of the project have been i) the characterization of the differences in particle concentrations measured by SPIN units and other CFDCs under different meteorological conditions; ii) the characterization and investigation about features of the parallel plate type CFDC to better learn how to calibrate instruments of this type and in what detail the calibration is necessary; iii) the improvement of methods and procedures to minimize frost background in SPIN, isolating the effects that lead to frost formation and implementing changes in the procedure that might arise in frost; iv) improved measurement of ice crystal concentrations by utilizing advanced analysis techniques of particle-by-particle polarization ratio.

### EKO Instruments EUROPE BV (The Netherlands) @ Izaña Subtropical Access Facility (ISAF, Spain)
EKO Instruments EUROPE BV is a Dutch company established in 1927 with three core business areas, which are remote sensing, evaluation and measurement of photovoltaic performance, and radiation and spectral measurements.

The research project main purpose is the evaluation of the EKO MS-711 spectroradiometer measurements at the Izaña Subtropical Access Facility (ISAF, Spain). The project foresees an intercomparison between instruments provided by EKO as well as other radiometers already installed at IARC-AEMET testbed in order to perform i) comparison of the direct normal irradiance measurements performed by the collimated and rotating shadow band EKO spectroradiometers; ii) evaluation and comparison of current methods for the retrieval of aerosol optical depth (AOD), precipitable water vapor (PWV), and the spectral irradiance extension, based on spectral DNI measurements from both collimated and RSB MS-711, iii) comparison between indoor and outdoor spectroradiometer calibrations; and to iv) quantify the measurement improvements in the measurement accuracy of the stray light corrected DNI measurements of the EKO spectroradiometer in the UV range against the NASA Pandora spectrometer; v) quantify the measurement improvements in the measurement accuracy of the stray light correction measurements of the EKO spectroradiometer. During the visit has been foreseen the assembly of instrumentation on site for the measurement campaign. Two spectroradiometers will be provided by EKO Instruments to be installed in Izaña testbed. One collimated EKO MS-711 will be installed with collimation in an EKO STR-22G sun tracker and one EKO MS-711 will be installed in the EKO RSB-01S rotating shadow band.

### Enviconcontrol SA (Belgium) @ CNR IMAA Atmospheric Observatory (CIAO, Italy)

Enviconcontrol is specialized in measuring equipment for gases, air and dust (sampling, analysis, calibration and generating of gases), as well as in acquisition and management systems for monitoring and warning networks. The SME has exclusive dealership for about 15 manufacturers in Benelux, France, and Africa. Enviconcontrol has participated in the measurement campaign INTERACT-II (INTERcomparison of Aerosol and Cloud Tracking) where a number of commercial instruments were involved: two multi-wavelength Raman lidars, a Raymetrics UV scanning Raman lidar, a VAISALA CT25K ceilometer, a VAISALA CL51 ceilometer, a JENOPTIK CHM15k ceilometer, a Campbell CS135s ceilometer, and a Sigma Space mini-Micro Pulse Lidar. Enviconcontrol has been in charge of operating the mini-MPL system to study the system performance for the measurements of aerosols and clouds, instrument stability, and accuracy of calibration. Enviconcontrol furthermore received training for advanced Raman lidar operation and use of calibration procedure for the lidar depolarization technique.

### GRASP S.A.S (France) @ FINOKALIA Atmospheric Observatory (FKL, Greece)

The objective of the GLAM (Comparison of GARRLIC Absorption Profiles with Airborne In-situ Measurements during the DETECT Campaign in Crete) campaign was the evaluation of the GARRLiC retrievals with high-quality airborne and in-situ measurements of aerosol absorption performed during the campaign at Finokalia. The TNA was carried out by the start-up company GRASP S.A.S.

### IONICON Analytik (Austria) @ TROPOS Research Station Melpitz (MEL, Germany)

The main scientific objective of this TNA is to field test and validate the new CHARON PTR-TOF 6000 X2 instrument. The instrument detects gas-phase organics at single-digit ppt levels and particle-phase organics at triple-digit pg/m³ levels. The instrument exhibits a series of user friendly features such as automated zeroing, automated switching between gas phase and
EKO Instruments EUROPE BV is a Dutch company established in 1927 with three core business areas, which are remote sensing, evaluation and measurement of photovoltaic performance, and radiation and spectral measurements.

The research project main purpose is the evaluation of the EKO MS-711 spectroradiometer measurements at the Izaña Subtropical Access Facility (ISAF, Spain). The project foresees an intercomparison between instruments provided by EKO as well as other radiometers already installed at IARC-AEMET testbed in order to perform i) comparison of the direct normal irradiance measurements performed by the collimated and rotating shadow band EKO spectroradiometers; ii) evaluation and comparison of current methods for the retrieval of aerosol optical depth (AOD), precipitable water vapor (PWV), and the spectral irradiance extension, based on spectral DNI measurements from both collimated and RSB MS-711, iii) comparison between indoor and outdoor spectroradiometer calibrations; and to iv) quantify the measurement improvements in the measurement accuracy of the stray light corrected DNI measurements of the EKO spectroradiometer in the UV range against the NASA Pandora spectrometer; v) quantify the measurement improvements in the measurement accuracy of the stray light correction measurements of the EKO spectroradiometer. During the visit has been foreseen the assembly of instrumentation on site for the measurement campaign. Two spectroradiometers will be provided by EKO Instruments to be installed in Izaña testbed. One collimated EKO MS-711 will be installed with collimation in an EKO STR-22G sun tracker and one EKO MS-711 will be installed in the EKO RSB-01S rotating shadow band.

### Enviconcontrol SA (Belgium) @ CNR IMAA Atmospheric Observatory (CIAO, Italy)

Enviconcontrol is specialized in measuring equipment for gases, air and dust (sampling, analysis, calibration and generating of gases), as well as in acquisition and management systems for monitoring and warning networks. The SME has exclusive dealership for about 15 manufacturers in Benelux, France, and Africa. Enviconcontrol has participated in the measurement campaign INTERACT-II (INTERcomparison of Aerosol and Cloud Tracking) where a number of commercial instruments were involved: two multi-wavelength Raman lidars, a Raymetrics UV scanning Raman lidar, a VAISALA CT25K ceilometer, a VAISALA CL51 ceilometer, a JENOPTIK CHM15k ceilometer, a Campbell CS135s ceilometer, and a Sigma Space mini-Micro Pulse Lidar. Enviconcontrol has been in charge of operating the mini-MPL system to study the system performance for the measurements of aerosols and clouds, instrument stability, and accuracy of calibration. Enviconcontrol furthermore received training for advanced Raman lidar operation and use of calibration procedure for the lidar depolarization technique.

### GRASP S.A.S (France) @ FINOKALIA Atmospheric Observatory (FKL, Greece)

The objective of the GLAM (Comparison of GARRLIC Absorption Profiles with Airborne In-situ Measurements during the DETECT Campaign in Crete) campaign was the evaluation of the GARRLiC retrievals with high-quality airborne and in-situ measurements of aerosol absorption performed during the campaign at Finokalia. The TNA was carried out by the start-up company GRASP S.A.S.

### IONICON Analytik (Austria) @ TROPOS Research Station Melpitz (MEL, Germany)

The main scientific objective of this TNA is to field test and validate the new CHARON PTR-TOF 6000 X2 instrument. The instrument detects gas-phase organics at single-digit ppt levels and particle-phase organics at triple-digit pg/m³ levels. The instrument exhibits a series of user friendly features such as automated zeroing, automated switching between gas phase and
particle inlet and real-time display of concentrations. IONICON will provide a PTR-TOF 6000 X2 instrument that is equipped with the latest version of the CHARON particle inlet. The CHARON ("Chemical Analysis of Aerosol On-line") inlet consists of i) a gas-phase denuder for removing gaseous organics, ii) an aerodynamic lens for enriching the particle concentration in the instrument subsampling flow and iii) a vaporization unit for evaporating particle-bound organics [Eichler et al.; doi: 10.5194/amt-8-1353-2015; Müller et al., doi: 0.1021/acs.analchem.7b02582] The commercial instrument offers a variety of new features (automated zeroing, automated switching between gas phase and particle inlet, real-time display of concentrations, sub-ng detection limit, new vaporizer design) that have not been field-tested and validated. Dr. Markus Müller, the developer of both the PTR-TOF-MS instrument and the CHARON inlet, will set-up, calibrate and operate the CHARON-PTR-ToF-MS analyzer during week 1. During week 2 remote operation will be tested. During week 3, the PhD student Felix Piel will be on site for training purposes together with his supervisor Prof. Armin Wisthaler who has also multi-year experience in PTR-ToF-MS and particle analysis using the CHARON inlet. This will be the first medium-term field test and validation exercise of the new CHARON-PTR-ToF-MS analyzer. Data analysis and write-up (method/intercomparison paper) will be carried out in joined work by IONICON, the University of Oslo and TROPOS. The TNA will end the 1st of March 2019 and a complete scientific report will be published.

### Palas GmbH (Germany) @ Puy de Dome high altitude station (PUY, France)

Palas is a company specialized in particle measurement technology and the development and production of filter test systems and optical aerosol spectrometers. In October 2016, Palas participated in an intercomparison field campaign of cloud microphysical probes with two of its Fidas® 200 S instruments. Fidas® 200 S is a fine dust monitoring and ambient air measurement system for ambient air monitoring of fine dust for regulatory purposes. Goal of this campaign is to evaluate a new automatic instrumentation for clouds droplet real time analysis. The new Fidas® 200 analyser supplies a particle size distribution (mass and/or number) between 0,4 and 40 µm. The aim is to study the interaction between droplets size and condensation nucleus with two analysers, installed side by side. One is configured to measure droplets size, the other to dry droplets and to evaluate condensation nucleus size. If successful, the low-cost and low maintenance instrument could be an efficient solution for long-term measurement of cloud droplets at ACTRIS stations.

### Palas GmbH & Airlip Service GmbH (Germany) @ Pallas-Sodankylä Global Atmospheric Watch Station (PAL, Finland)

The 7th Pallas Cloud Experiment combined in-situ and remote-sensing observations to provide the best basis for process-level research on cloud-atmosphere interaction.

Palas GmbH together with Airlip Service GmbH & Co KG provided a Fidas Fly 200 instrument and flight robot (HORUS 2.0 octocopter), respectively during this campaign.

Fidas Fly200 provided the continuous and simultaneous measurement of the PM-fractions PM1, PM2.5, PM4, PM10, as well as in addition the particle number concentration as well as the particle size distribution in 32 size classes per decade within the particle size range of 0.18 – 18 µm or 0.5 – 40 µm - and all this in an additional spatial dimension. Besides the experiments were the first time to actually use the new Fidas Fly 200 in combination with HORUS in such weather conditions, regarding humidity and temperature. This proves that the system works and shows what needs to be improved.
particle inlet and real-time display of concentrations. IONICON will provide a PTR-TOF 6000 X2 instrument that is equipped with the latest version of the CHARON particle inlet. The CHARON ("Chemical Analysis of Aerosol On-line") inlet consists of i) a gas-phase denuder for removing gaseous organics, ii) an aerodynamic lens for enriching the particle concentration in the instrument subsampling flow and iii) a vaporization unit for evaporating particle-bound organics [Eichler et al.; doi: 10.5194/amt-8-1353-2015; Müller et al., doi: 0.1021/acs.analchem.7b02582] The commercial instrument offers a variety of new features (automated zeroing, automated switching between gas phase and particle inlet, real-time display of concentrations, sub-ng detection limit, new vaporizer design) that have not been field-tested and validated. Dr. Markus Müller, the developer of both the PTR-TOF-MS instrument and the CHARON inlet, will set-up, calibrate and operate the CHARON-PTR-ToF-MS analyzer during week 1. During week 2 remote operation will be tested. During week 3, the PhD student Felix Piel will be on site for training purposes together with his supervisor Prof. Armin Wisthaler who has also multi-year experience in PTR-ToF-MS and particle analysis using the CHARON inlet. This will be the first medium-term field test and validation exercise of the new CHARON-PTR-ToF-MS analyzer. Data analysis and write-up (method/intercomparison paper) will be carried out in joined work by IONICON, the University of Oslo and TROPOS. The TNA will end the 1st of March 2019 and a complete scientific report will be published.

### Palas GmbH (Germany) @ Puy de Dome high altitude station (PUY, France)

Palas is a company specialized in particle measurement technology and the development and production of filter test systems and optical aerosol spectrometers. In October 2016, Palas participated in an intercomparison field campaign of cloud microphysical probes with two of its Fidas® 200 S instruments. Fidas® 200 S is a fine dust monitoring and ambient air measurement system for ambient air monitoring of fine dust for regulatory purposes. Goal of this campaign is to evaluate a new automatic instrumentation for clouds droplet real time analysis. The new Fidas® 200 analyser supplies a particle size distribution (mass and/or number) between 0,4 and 40 µm. The aim is to study the interaction between droplets size and condensation nucleus with two analysers, installed side by side. One is configured to measure droplets size, the other to dry droplets and to evaluate condensation nucleus size. If successful, the low-cost and low maintenance instrument could be an efficient solution for long-term measurement of cloud droplets at ACTRIS stations.

### Palas GmbH & Airlip Service GmbH (Germany) @ Pallas-Sodankylä Global Atmospheric Watch Station (PAL, Finland)

The 7th Pallas Cloud Experiment combined in-situ and remote-sensing observations to provide the best basis for process-level research on cloud-atmosphere interaction.

Palas GmbH together with Airlip Service GmbH & Co KG provided a Fidas Fly 200 instrument and flight robot (HORUS 2.0 octocopter), respectively during this campaign.

Fidas Fly200 provided the continuous and simultaneous measurement of the PM-fractions PM1, PM2.5, PM4, PM10, as well as in addition the particle number concentration as well as the particle size distribution in 32 size classes per decade within the particle size range of 0.18 – 18 µm or 0.5 – 40 µm - and all this in an additional spatial dimension. Besides the experiments were the first time to actually use the new Fidas Fly 200 in combination with HORUS in such weather conditions, regarding humidity and temperature. This proves that the system works and shows what needs to be improved.
Raymetrics (Greece) @ SIRTA Atmospheric Research Observatory (SIR, France)

The objective of this TNA has been the development of new software and hardware tools for improving lidar alignment mechanism and strategies and optimizing lidars field of view. In many lidar systems optimizing day light background suppression mechanism is based on reducing the lidar's field of view. However, minimizing field of view requires an improved “mechanism” for lidar alignment. By using a combination of a special designed CCD camera and multi-anode PMT, lidar signal optimization and accurate positioning of the field stop of the lidar was accomplished. Monitoring the image of the telescope focal plane and detecting the position of the lidar return signals in respect of Field Stop Diameter allows user to check the “correct” position of the Field Stop and the quality of the lidar alignment. The use of a multi-anode PMT and specially developed software allows real time alignment monitoring and correction by a motorized laser beam steering mechanism. The unique combination of a CCD and a multi-anode PMT opens new ways for checking lidar alignment, lidar setup integrity and lidar signal background suppression. A better positioning of the Near Range field stop achieved even from the very first day of these TNA. Near ranges signals were improved significantly and telecover test performed successfully. CCD camera solutions were deployed and checked. It was proved that such solutions can be used successfully for visible but also for ultra violet signals day and night for IPRAL lidar.

Sunset Laboratory Inc. (The Netherlands) @ CSIC Montseny (MSY, Spain)

Sunset Laboratory Inc. is a company specialized for manufacturing devices for organic carbon and elemental carbon (OC-EC) aerosol analysis and in the field of aviation, mining, marine, astronomy, construction, and weather research. Their equipment is suitable for the laboratory or in the field, and ready for use with different methods, among others the EUSAAR2 protocol developed within the ACTRIS-1 predecessor EU project. Sunset Laboratory has developed the Sunset SemiContinuous Field OCEC analyzer. To evaluate its performance with the EUSAAR2 protocol, Sunset Laboratory has used the ACTRIS-2 site MSY during a TNA project "SLOPE". The EUSAAR2 is a required protocol for the networks of all EU member states to measure EC and OC in particulate matter at background sites according to the Council Directive 2008/50/EC on ambient air quality and cleaner air for Europe. The European Committee of Standardization (CEN), has recently adopted EUSAAR2 as the reference temperature protocol to be used when performing the offline, thermal-optical/transmittance (TOT) Organic and Elemental Carbon analysis (OCEC) (CEN/TC 264/WG 35 prEN16909:2016). Sunset investigates the comparison of the online OCEC analysis method with the offline, reference method at a challenging rural environment, dominated by biogenic emissions, for their comparability and to evaluate the hightime resolution concentrations.

Profile of the users

Figure 6 shows the different sector representation including the private sector, the public sector (universities and research institutes) within the projects carried out. The majority of users having used the observational platform have come from the public research sector.
Raymetrics (Greece) @ SIRTA Atmospheric Research Observatory (SIR, France)

The objective of this TNA has been the development of new software and hardware tools for improving lidar alignment mechanism and strategies and optimizing lidars field of view. In many lidar systems optimizing day light background suppression mechanism is based on reducing the lidar's field of view. However, minimizing field of view requires an improved “mechanism” for lidar alignment. By using a combination of a special designed CCD camera and multi-anode PMT, lidar signal optimization and accurate positioning of the field stop of the lidar was accomplished. Monitoring the image of the telescope focal plane and detecting the position of the lidar return signals in respect of Field Stop Diameter allows user to check the “correct” position of the Field Stop and the quality of the lidar alignment. The use of a multi-anode PMT and specially developed software allows real time alignment monitoring and correction by a motorized laser beam steering mechanism. The unique combination of a CCD and a multi-anode PMT opens new ways for checking lidar alignment, lidar setup integrity and lidar signal background suppression. A better positioning of the Near Range field stop achieved even from the very first day of these TNA. Near ranges signals were improved significantly and telecover test performed successfully. CCD camera solutions were deployed and checked. It was proved that such solutions can be used successfully for visible but also for ultra violet signals day and night for IPRAL lidar.

Sunset Laboratory Inc. (The Netherlands) @ CSIC Montseny (MSY, Spain)

Sunset Laboratory Inc. is a company specialized for manufacturing devices for organic carbon and elemental carbon (OC-EC) aerosol analysis and in the field of aviation, mining, marine, astronomy, construction, and weather research. Their equipment is suitable for the laboratory or in the field, and ready for use with different methods, among others the EUSAAR2 protocol developed within the ACTRIS-1 predecessor EU project. Sunset Laboratory has developed the Sunset SemiContinuous Field OCEC analyzer. To evaluate its performance with the EUSAAR2 protocol, Sunset Laboratory has used the ACTRIS-2 site MSY during a TNA project "SLOPE". The EUSAAR2 is a required protocol for the networks of all EU member states to measure EC and OC in particulate matter at background sites according to the Council Directive 2008/50/EC on ambient air quality and cleaner air for Europe. The European Committee of Standardization (CEN), has recently adopted EUSAAR2 as the reference temperature protocol to be used when performing the offline, thermal-optical/transmittance (TOT) Organic and Elemental Carbon analysis (OCEC) (CEN/TC 264/WG 35 prEN16909:2016). Sunset investigates the comparison of the online OCEC analysis method with the offline, reference method at a challenging rural environment, dominated by biogenic emissions, for their comparability and to evaluate the hightime resolution concentrations.

Profile of the users

Figure 6 shows the different sector representation including the private sector, the public sector (universities and research institutes) within the projects carried out. The majority of users having used the observational platform have come from the public research sector.
<figure><img src="image_11.png" /><figcaption>Figure 6: Representation of public sector (Research, Universities) and private sector (SME) in the number of TNA projects carried out during the ACTRIS-2 project.</figcaption></figure>

The research domain targeted by the completed TNA projects are well distributed among the three ACTRIS topics aerosol profiling (35%), cloud profiling (21%) and trace gases and near surface aerosol (44%), as summarized in figure 7 below.

<figure><img src="image_12.png" /><figcaption>Figure 7: Representation of project users in aerosol profiling domain, cloud profiling and near surface aerosol properties and trace gases.</figcaption></figure>

A significant number of users have benefitted from the opportunities offered through ACTRIS-2 TNA: 371 researchers (representing 140% of 264 initially estimated users, as in Annex 1 of the grant agreement) have been able to benefit from TNA to the advanced observational facilities, of which 88% are new users, demonstrating that ACTRIS-2 has been successful in promoting the use of its facilities to users that have never visited the ACTRIS stations for research before (See Figure 8), including scientists young researchers and scientists from new regions/countries. 34% of the researchers are female scientists (see Figure 9). 28% (undergraduate and postgraduate) of the researchers were young scientists as shown in Figure 10, 28% of the projects aimed at training purposes (to get trained in observation measurements,
<figure><img src="image_11.png" /><figcaption>Figure 6: Representation of public sector (Research, Universities) and private sector (SME) in the number of TNA projects carried out during the ACTRIS-2 project.</figcaption></figure>

The research domain targeted by the completed TNA projects are well distributed among the three ACTRIS topics aerosol profiling (35%), cloud profiling (21%) and trace gases and near surface aerosol (44%), as summarized in figure 7 below.

<figure><img src="image_12.png" /><figcaption>Figure 7: Representation of project users in aerosol profiling domain, cloud profiling and near surface aerosol properties and trace gases.</figcaption></figure>

A significant number of users have benefitted from the opportunities offered through ACTRIS-2 TNA: 371 researchers (representing 140% of 264 initially estimated users, as in Annex 1 of the grant agreement) have been able to benefit from TNA to the advanced observational facilities, of which 88% are new users, demonstrating that ACTRIS-2 has been successful in promoting the use of its facilities to users that have never visited the ACTRIS stations for research before (See Figure 8), including scientists young researchers and scientists from new regions/countries. 34% of the researchers are female scientists (see Figure 9). 28% (undergraduate and postgraduate) of the researchers were young scientists as shown in Figure 10, 28% of the projects aimed at training purposes (to get trained in observation measurements,
scientific integration, for developing specific expertise, or to benefit from a facility which is not
available in the home country of the researchers), 48% contributed to mobility of experts (e.g.,
for participation in scientific campaigns, for instrumental synergies, to carry out
interdisciplinary research project or collaborative campaigns), and 24% represented a
combination of both, training and mobility. A representation of the training is as in Figure 11.

<figure><img src="image_13.png" /><figcaption>Figure 8: Representation of new TNA users</figcaption></figure>

<figure><img src="image_14.png" /><figcaption>Figure 9: Representation of female TNA users.</figcaption></figure>

<figure><img src="image_15.png" /><figcaption>Figure 10: Representation of user profile ranging from expert, post graduate, post doctorate, technician, undergraduate.</figcaption></figure>
scientific integration, for developing specific expertise, or to benefit from a facility which is not
available in the home country of the researchers), 48% contributed to mobility of experts (e.g.,
for participation in scientific campaigns, for instrumental synergies, to carry out
interdisciplinary research project or collaborative campaigns), and 24% represented a
combination of both, training and mobility. A representation of the training is as in Figure 11.

<figure><img src="image_13.png" /><figcaption>Figure 8: Representation of new TNA users</figcaption></figure>

<figure><img src="image_14.png" /><figcaption>Figure 9: Representation of female TNA users.</figcaption></figure>

<figure><img src="image_15.png" /><figcaption>Figure 10: Representation of user profile ranging from expert, post graduate, post doctorate, technician, undergraduate.</figcaption></figure>
<figure><img src="image_16.png" /><figcaption>Figure 11: A representation of the projects submitted for different purposes.</figcaption></figure>

## 5 Description of Transnational Access

The transnational access activities are described by observational facility and direct scientific output resulting from TNA is summarized in scientific activity reports available on the ACTRIS website at https://www.actris.eu/Documentation/ACTRIS-2IAinH2020(2015-2019)/WPdocuments/TNAOverview/Physical.aspx. A short overview of TNA activities at each individual station is described below.

Figure 12 below illustrates the use of the 18 individual stations. One station has provided no access (HYM) and although some stations have provided fewer access (e.g., CESAR, MEL), some others have overspend the minimum quantity of access due to the high user demand (e.g., CMN, JFJ, FKL, GRA, MAIDO).
<figure><img src="image_16.png" /><figcaption>Figure 11: A representation of the projects submitted for different purposes.</figcaption></figure>

## 5 Description of Transnational Access

The transnational access activities are described by observational facility and direct scientific output resulting from TNA is summarized in scientific activity reports available on the ACTRIS website at https://www.actris.eu/Documentation/ACTRIS-2IAinH2020(2015-2019)/WPdocuments/TNAOverview/Physical.aspx. A short overview of TNA activities at each individual station is described below.

Figure 12 below illustrates the use of the 18 individual stations. One station has provided no access (HYM) and although some stations have provided fewer access (e.g., CESAR, MEL), some others have overspend the minimum quantity of access due to the high user demand (e.g., CMN, JFJ, FKL, GRA, MAIDO).
<figure><img src="image_17.png" /><figcaption>Figure 12: Number of access days per individual station (planned access vs total access provided)</figcaption></figure>

## 5.1 CNR IMAA Atmospheric Observatory, CIAO (CNR)

CIAO has hosted ten TNA projects, for a total duration of 140 days. accounting for near 100% of the access offered.

CIAO-1: Within the project, named MICROLIRA, 11 access days, (MICROphysical characterization of cirrus clouds by LIidar and RAdar instruments), the vertical profile of dust and cirrus cloud extinction coefficient retrieved using the Raman Lidar technique has been compared with the current MPLNET V3 extinction retrieval obtained from micro-pulse lidars, which is based on the assumption of the value of the extinction-to-backscatter ratio (Lidar Ratio). The vertical profile of the extinction coefficient is a fundamental climate variable to estimate the radiative forcing and the microphysical properties of atmospheric particles. Moreover, cirrus cloud extinction coefficient is required in the Heymsfield parameterization to calculate cirrus clouds mean crystal size and Ice Water Content (IWC): both the extinction coefficient and the IWC are input parameters for the Fu-Liou-Gu (FLG) radiative transfer code to calculate TOA forcing. The work carried out in the frame of MICROLIRA has allowed to quantify the sensitivity of the Fu-Liou-Gu (FLG) Radiative Transfer Model to estimate the aerosol-cloud net radiative forcing using different lidar instruments/algorithms/techniques applied to the retrieval of the extinction coefficient and in particular the effect of the smoothing of lidar profiles. The effect of smoothing on the atmospheric features of the original vertical lidar profile is resulted substantive and must be taken into account when a radiative analysis is performed with pre-processed lidar data.

The results of the project have been presented at EGU 2016, DUST 2016, and at ICCP 2016 collecting good feedbacks; a journal article will be also submitted by the end of the year.

CIAO-2: For the INTERACT-II project, 4 days, commercial ceilometers and a miniMPL lidar have been inter-compared in the frame of the INTERACT-II campaign and this was performed at CIAO (CNR-IMAA Atmospheric Observatory) in Tito Scalo, Potenza, Italy (760 m a.s.l.,
<figure><img src="image_17.png" /><figcaption>Figure 12: Number of access days per individual station (planned access vs total access provided)</figcaption></figure>

## 5.1 CNR IMAA Atmospheric Observatory, CIAO (CNR)

CIAO has hosted ten TNA projects, for a total duration of 140 days. accounting for near 100% of the access offered.

CIAO-1: Within the project, named MICROLIRA, 11 access days, (MICROphysical characterization of cirrus clouds by LIidar and RAdar instruments), the vertical profile of dust and cirrus cloud extinction coefficient retrieved using the Raman Lidar technique has been compared with the current MPLNET V3 extinction retrieval obtained from micro-pulse lidars, which is based on the assumption of the value of the extinction-to-backscatter ratio (Lidar Ratio). The vertical profile of the extinction coefficient is a fundamental climate variable to estimate the radiative forcing and the microphysical properties of atmospheric particles. Moreover, cirrus cloud extinction coefficient is required in the Heymsfield parameterization to calculate cirrus clouds mean crystal size and Ice Water Content (IWC): both the extinction coefficient and the IWC are input parameters for the Fu-Liou-Gu (FLG) radiative transfer code to calculate TOA forcing. The work carried out in the frame of MICROLIRA has allowed to quantify the sensitivity of the Fu-Liou-Gu (FLG) Radiative Transfer Model to estimate the aerosol-cloud net radiative forcing using different lidar instruments/algorithms/techniques applied to the retrieval of the extinction coefficient and in particular the effect of the smoothing of lidar profiles. The effect of smoothing on the atmospheric features of the original vertical lidar profile is resulted substantive and must be taken into account when a radiative analysis is performed with pre-processed lidar data.

The results of the project have been presented at EGU 2016, DUST 2016, and at ICCP 2016 collecting good feedbacks; a journal article will be also submitted by the end of the year.

CIAO-2: For the INTERACT-II project, 4 days, commercial ceilometers and a miniMPL lidar have been inter-compared in the frame of the INTERACT-II campaign and this was performed at CIAO (CNR-IMAA Atmospheric Observatory) in Tito Scalo, Potenza, Italy (760 m a.s.l.,
40.60°N, 15.72°E) from July 2016. The stability, sensitivity and uncertainties of these commercial automatic lidars and ceilometers for tropospheric profiling of aerosols and clouds have been evaluated, using advanced research lidars as reference. The instruments involved in the campaign have been: Luftt CHM15k, Vaisala CT25K, VAISALA CL51, Campbell CS135, Sigma Space mini-Micro Pulse Lidar (MPL). The last three instruments have been deployed by the related manufacturers which have also provided their support in the data evaluation.

CIAO-3 was withdrawn by CIMEL due to inability to go to the station.

CIAO-4: Satellite validation using ground based lidar measurements. The project developed and provided a collocation match up database and associated graphical user interface tools for aerosol reference quality observations. The tool is developed in synergy with the GAIA-CLIM project with the aim to allow the users to easily investigate the temporal congruence with EO measurements.

CIAO-5: TRAining on Lidar INstrument for ATmospheric studies on Aerosol and Clouds to BMKG (Indonesia). The training have added knowledge and skills on how to manage and analyze the data from Lidar observation. Study how to manage and analyze the lidar data in ascii format will be done in the future.

CIAO-6: The tools developed at CIAO facilities for visualization and fast analysis of the aerosol lidar data has been presented and described into details to the Proposer. With the guidance, training and support of the CIAO experts, the algorithmic tool that provides automated remote access to the Single Calculus Chain has been introduced to the Proposer. More specifically, the tool was modified and the automated upload of the lidar measurement files of the station as well as the ancillary files that include the overlap function, the atmospheric sounding and the lidar ratio profiles has been achieved for the station of Thessaloniki.

CIAO-7: In this project, a lidar-based approach to identify different aerosol types and to separate the profiles of highly and weakly depolarizing particles has been tested. Moreover, this approach enabled us to derive the mass concentrations of coarse-mode and fine-mode particles, based on sun photometer observations. This method can be easily applied in several desert dust and BBA cases by assuming that we have no more than two dominant types and that each aerosol type consists exclusively by fine-mode or coarse-mode particles. Further analysis of Saharan dust intrusions over the southern Europe will allow to extend the application of our lidar-photometer method to dust observations taken over Athens, Greece by the NTUA lidar station (EARLINET).

CIAO-8: The project was configured as a mobility of experts to allow CIAO staff to learn also how to use the code implemented by Veselovskii et al. (2015) to invert lidar measurements to the particle microphysical properties using regularization algorithm, considering both spherical and spheroidal kernel functions. Different sets of multiwavelength lidar observations have been used and in particular dust episodes over CIAO station. A comparative analysis to parameters obtained at SHADOW campaign has been also carried out. Results are under evaluation for future publications.

CIAO-9: The measurement campaign was performed in Potenza. CMA LIDAR have been compared with MUSA Potenza lidar. The comparison shows a good agreement between the signals coming from the two LIDAR systems. It also suggests to furtherly investigate the results of the measurements, in order to understand if the signal pre-processing and the experimental set-up must be improved, to verify the calibration of the depolarization channel and to test the
40.60°N, 15.72°E) from July 2016. The stability, sensitivity and uncertainties of these commercial automatic lidars and ceilometers for tropospheric profiling of aerosols and clouds have been evaluated, using advanced research lidars as reference. The instruments involved in the campaign have been: Luftt CHM15k, Vaisala CT25K, VAISALA CL51, Campbell CS135, Sigma Space mini-Micro Pulse Lidar (MPL). The last three instruments have been deployed by the related manufacturers which have also provided their support in the data evaluation.

CIAO-3 was withdrawn by CIMEL due to inability to go to the station.

CIAO-4: Satellite validation using ground based lidar measurements. The project developed and provided a collocation match up database and associated graphical user interface tools for aerosol reference quality observations. The tool is developed in synergy with the GAIA-CLIM project with the aim to allow the users to easily investigate the temporal congruence with EO measurements.

CIAO-5: TRAining on Lidar INstrument for ATmospheric studies on Aerosol and Clouds to BMKG (Indonesia). The training have added knowledge and skills on how to manage and analyze the data from Lidar observation. Study how to manage and analyze the lidar data in ascii format will be done in the future.

CIAO-6: The tools developed at CIAO facilities for visualization and fast analysis of the aerosol lidar data has been presented and described into details to the Proposer. With the guidance, training and support of the CIAO experts, the algorithmic tool that provides automated remote access to the Single Calculus Chain has been introduced to the Proposer. More specifically, the tool was modified and the automated upload of the lidar measurement files of the station as well as the ancillary files that include the overlap function, the atmospheric sounding and the lidar ratio profiles has been achieved for the station of Thessaloniki.

CIAO-7: In this project, a lidar-based approach to identify different aerosol types and to separate the profiles of highly and weakly depolarizing particles has been tested. Moreover, this approach enabled us to derive the mass concentrations of coarse-mode and fine-mode particles, based on sun photometer observations. This method can be easily applied in several desert dust and BBA cases by assuming that we have no more than two dominant types and that each aerosol type consists exclusively by fine-mode or coarse-mode particles. Further analysis of Saharan dust intrusions over the southern Europe will allow to extend the application of our lidar-photometer method to dust observations taken over Athens, Greece by the NTUA lidar station (EARLINET).

CIAO-8: The project was configured as a mobility of experts to allow CIAO staff to learn also how to use the code implemented by Veselovskii et al. (2015) to invert lidar measurements to the particle microphysical properties using regularization algorithm, considering both spherical and spheroidal kernel functions. Different sets of multiwavelength lidar observations have been used and in particular dust episodes over CIAO station. A comparative analysis to parameters obtained at SHADOW campaign has been also carried out. Results are under evaluation for future publications.

CIAO-9: The measurement campaign was performed in Potenza. CMA LIDAR have been compared with MUSA Potenza lidar. The comparison shows a good agreement between the signals coming from the two LIDAR systems. It also suggests to furtherly investigate the results of the measurements, in order to understand if the signal pre-processing and the experimental set-up must be improved, to verify the calibration of the depolarization channel and to test the
retrieval of the optical parameters. The CMA has established an integrated meteorological
observing system incorporating space-based, airborne and ground-based observations, which
has steadily improved the accuracy of weather forecasts and climate predictions. The technical
staff of CMA during the measurement campaign in Italy benefitted of the training at the CIAO
infrastructure on both theoretical and experimental domain.

CIAO-10: The main objective of this TNA project was the training of the participants to the usage of the Single Calculus Chain (SCC). The SCC training consisted in 3 full days at the end of which the participants were able to setup (beginners) and optimize (advanced users) the SCC platform in order to homogenize the lidar processing and the quality assurance procedures. One of the main issues in research and satellite validation is the integration of the observations from the different networks. Some of these structures have developed operation procedures that allow a strict control on the data quality. Nevertheless, there is a lot of work to be done to homogenize these programs and procedures for a global perspective. The harmonization of standard operation procedures between different lidar stations and networks is the first step towards an operational infrastructure, enabling its contribution to GALION and its support to satellite atmospheric missions and joint research activities from a global perspective. The SCC platform is one of the tools that can provide means for this harmonization from the data format and processing perspective. The use of such a platform can enable new opportunities for the research institutions that employ it.

CIAO-11: The data collected with the MUSA Raman lidar system deployed at CIAO has been used jointly with the technique developed by Lolli et al., 2013 to retrieve the precipitation median volumetric size through multi-wavelength lidar measurements. The scanning of the available has allowed to detect only one recent case study with 24 hours of data. Nevertheless, a concept for the identification of suitable measurement scenarios has been developed and a three-level algorithm or the measurement screening has been designed. The method will be expanded in future to be tested on to other different lidar system within EARLINET.

The collective effort of the different experts working within the CIAO staff, involving scientist, technicians and software developers has allowed the successful implementation of the TNA projects and allowed to provide scientific results presented at conferences and peer-reviewed literature. TNA projects has also allowed to establish a good synergy with other H2020 projects (e.g. GAIA-CLIM) and with the work carried out by lidar/ceilometer manufacturers.

**5.2 Monte Cimone taking advantage of Po Valley facility, CMN (CNR)**

In total, CMN has hosted 7 projects, accounting for 114 access days.

CMN-1: During the first reporting period, the NICE project provided 8 access days to Basel University participants and was focused to study the variability of INPs of biological origin on a broader spatial scale. In fact it constitutes a first structure of such connection of Observatories, including Monte Cimone, Jungfraujoch, Puy de Dome, Izana and Haldde. NICE project was successful in collecting the first data on INPs of biological origin at Monte Cimone. Preliminary results confirm that at Cimone the passage of front systems accounts for larger airborne INPs. This project also allowed collecting simultaneous samples for determining IN with two different techniques, one carried out in Basel and the other at ISAC-CNR. A scientific publication is planned including these results.

CMN2-7:
retrieval of the optical parameters. The CMA has established an integrated meteorological
observing system incorporating space-based, airborne and ground-based observations, which
has steadily improved the accuracy of weather forecasts and climate predictions. The technical
staff of CMA during the measurement campaign in Italy benefitted of the training at the CIAO
infrastructure on both theoretical and experimental domain.

CIAO-10: The main objective of this TNA project was the training of the participants to the usage of the Single Calculus Chain (SCC). The SCC training consisted in 3 full days at the end of which the participants were able to setup (beginners) and optimize (advanced users) the SCC platform in order to homogenize the lidar processing and the quality assurance procedures. One of the main issues in research and satellite validation is the integration of the observations from the different networks. Some of these structures have developed operation procedures that allow a strict control on the data quality. Nevertheless, there is a lot of work to be done to homogenize these programs and procedures for a global perspective. The harmonization of standard operation procedures between different lidar stations and networks is the first step towards an operational infrastructure, enabling its contribution to GALION and its support to satellite atmospheric missions and joint research activities from a global perspective. The SCC platform is one of the tools that can provide means for this harmonization from the data format and processing perspective. The use of such a platform can enable new opportunities for the research institutions that employ it.

CIAO-11: The data collected with the MUSA Raman lidar system deployed at CIAO has been
used jointly with the technique developed by Lolli et al., 2013 to retrieve the precipitation
median volumetric size through multi-wavelength lidar measurements. The scanning of the
available has allowed to detect only one recent case study with 24 hours of data. Nevertheless,
a concept for the identification of suitable measurement scenarios has been developed and a
three-level algorithm or the measurement screening has been designed. The method will be
expanded in future to be tested on to other different lidar system within EARLINET.

The collective effort of the different experts working within the CIAO staff, involving scientist, technicians and software developers has allowed the successful implementation of the TNA projects and allowed to provide scientific results presented at conferences and peer-reviewed literature. TNA projects has also allowed to establish a good synergy with other H2020 projects (e.g. GAIA-CLIM) and with the work carried out by lidar/ceilometer manufacturers.

## 5.2 Monte Cimone taking advantage of Po Valley facility, CMN (CNR)

In total, CMN has hosted 7 projects, accounting for 114 access days.

CMN-1: During the first reporting period, the NICE project provided 8 access days to Basel University participants and was focused to study the variability of INPs of biological origin on a broader spatial scale. In fact it constitutes a first structure of such connection of Observatories, including Monte Cimone, Jungfraujoch, Puy de Dome, Izana and Haldde. NICE project was successful in collecting the first data on INPs of biological origin at Monte Cimone. Preliminary results confirm that at Cimone the passage of front systems accounts for larger airborne INPs. This project also allowed collecting simultaneous samples for determining IN with two different techniques, one carried out in Basel and the other at ISAC-CNR. A scientific publication is planned including these results.

CMN2-7:
During the second reporting period, six TNA projects have been carried out at CMN for a total of 106 RWD provided. The AFPO project (AOD's with filter photometers observation at high mountain station, CMN-2) aim to use PFR filter photometers and MICROTOPS II (MT2) ozone monitoring for the determination of aerosol optical depth in a synergistic way. Despite that bad weather conditions which did not allow for the computation of the multiple parameters, the project has been important preparatory work for the use of the developed system (automatic MICROTOPS measurements). The majority of TNA projects focused on the JRA1 field campaign taking place at Monte Cimone and Po Valley during July 2017 which we opened for participation to external via TNA. It was an international effort to investigate aerosol optical properties with up-to-date techniques. The experiment mainly focused on observation and prediction of aerosol light absorption and the quantification of black carbon, in particular on the factors affecting the ability of BC to absorb solar radiation, i.e. its Mass Absorption Cross section (MAC).

In particular at Monte Cimone through the PaSCIM project (CMN-4) run a custom made photoacoustic instrument was assembled, calibrated and installed at Monte Cimone for testing the ability of the prototype to measure aerosol absorption at the low concentrations typically sampled at the site. Moreover samples were collected for off-line chemical and morphological analysis. The COLOSSEUM MtCMN (CMN-5) project was focused on the chemical properties of non-refractory submicron aerosols (NR-PM1: organics, nitrate, sulfate, ammonium and chloride), which together with black/elemental carbon measurements cover main components of sub-micron particulate matter (PM). The chemical composition of particles with high-time-resolution will help to characterise the sources and origins of particles and may clarify the condition affecting the variability in MAC. The projects CAPS-SSA (CMN-6) and AA-Ex-Sca-CMN (CMN-3) were concentrated on measurement in the Po Valley, at a urban and a rural site: Bologna and San Pietro Capofiume. At both sites a CAPS PMssa was transferred and installed for real-time and non-filter based extinction/scattering measurements. The CAPS PMssa simultaneously measures light extinction and scattering coefficients and thus the absorption (extinction minus scattering) on the same sample volume. The great advantage of this technique, in contrast of using two separate instruments to measure scattering and absorption, is that there is no need for wavelength correction. CMN-6 was carried out by an SME (Aerodyne Research Inc. for the characterization of the single-scattering albedo with their CAPS PMssa monitor.

The ZeMATRAP (CMN-7) project was carried out during the field campaign, with a goal on the gas phase measurements: the ACTRTIS-2 field campaign represented a good opportunity to fully deploy techniques and different remote sensing and in-situ instruments. An alt azimuth platform called MIGE - Multiple Input Geometry Equipment) was coupled through an optic fibre to the GASCODNG2 (Gas Analyzer Spectrometer Correlating Optical Differences-New Gen. Mod. 2) in order to increase the measurements capabilities of the instrument. The total content of NO2, O3, SO2 BrO, CHOCHO, H2CO and their vertical distributions were measured with a resolution of about 5 km.

In total, 114 access days were provided by CMN.

## 5.3 SIRTA Atmospheric Research Observatory, SIR (CNRS)

SIRTA Atmospheric Research Observatory welcomed 19 projects and has provided 213 access days which was the quantity of access foreseen in the project.
During the second reporting period, six TNA projects have been carried out at CMN for a total of 106 RWD provided. The AFPO project (AOD's with filter photometers observation at high mountain station, CMN-2) aim to use PFR filter photometers and MICROTOPS II (MT2) ozone monitoring for the determination of aerosol optical depth in a synergistic way. Despite that bad weather conditions which did not allow for the computation of the multiple parameters, the project has been important preparatory work for the use of the developed system (automatic MICROTOPS measurements). The majority of TNA projects focused on the JRA1 field campaign taking place at Monte Cimone and Po Valley during July 2017 which we opened for participation to external via TNA. It was an international effort to investigate aerosol optical properties with up-to-date techniques. The experiment mainly focused on observation and prediction of aerosol light absorption and the quantification of black carbon, in particular on the factors affecting the ability of BC to absorb solar radiation, i.e. its Mass Absorption Cross section (MAC).

In particular at Monte Cimone through the PaSCIM project (CMN-4) run a custom made photoacoustic instrument was assembled, calibrated and installed at Monte Cimone for testing the ability of the prototype to measure aerosol absorption at the low concentrations typically sampled at the site. Moreover samples were collected for off-line chemical and morphological analysis. The COLOSSEUM MtCMN (CMN-5) project was focused on the chemical properties of non-refractory submicron aerosols (NR-PM1: organics, nitrate, sulfate, ammonium and chloride), which together with black/elemental carbon measurements cover main components of sub-micron particulate matter (PM). The chemical composition of particles with high-time-resolution will help to characterise the sources and origins of particles and may clarify the condition affecting the variability in MAC. The projects CAPS-SSA (CMN-6) and AA-Ex-Sca-CMN (CMN-3) were concentrated on measurement in the Po Valley, at a urban and a rural site: Bologna and San Pietro Capofiume. At both sites a CAPS PMssa was transferred and installed for real-time and non-filter based extinction/scattering measurements. The CAPS PMssa simultaneously measures light extinction and scattering coefficients and thus the absorption (extinction minus scattering) on the same sample volume. The great advantage of this technique, in contrast of using two separate instruments to measure scattering and absorption, is that there is no need for wavelength correction. CMN-6 was carried out by an SME (Aerodyne Research Inc. for the characterization of the single-scattering albedo with their CAPS PMssa monitor.

The ZeMATRAP (CMN-7) project was carried out during the field campaign, with a goal on the gas phase measurements: the ACTRTIS-2 field campaign represented a good opportunity to fully deploy techniques and different remote sensing and in-situ instruments. An alt azimuth platform called MIGE - Multiple Input Geometry Equipment) was coupled through an optic fibre to the GASCODNG2 (Gas Analyzer Spectrometer Correlating Optical Differences-New Gen. Mod. 2) in order to increase the measurements capabilities of the instrument. The total content of NO2, O3, SO2 BrO, CHOCHO, H2CO and their vertical distributions were measured with a resolution of about 5 km.

In total, 114 access days were provided by CMN.

## 5.3 SIRTA Atmospheric Research Observatory, SIR (CNRS)

SIRTA Atmospheric Research Observatory welcomed 19 projects and has provided 213 access days which was the quantity of access foreseen in the project.
SIRTA-1 project, TREBOL, was by high frequency acquisition (1 Hz) of data from Doppler and/or Elastic lidar to investigate boundary layer turbulence by using the particle backscatter coefficient profiles, as the aerosols act as tracers.

SIRTA-2 project enabled a user from Chile to be trained in cloud radar operation and calibration. The work achieved contributed to the Master of Science thesis of the user.

SIRTA-3 project enabled a user from Ireland to test a retrieval algorithm developed for cloud microphysical properties based on cloud radar and microwave radiometer measurements. Retrievals were compared to in-situ measurements of droplet size distributions. The results have been submitted for publication (Dupont et al. 2018, submitted).

In the SIRTA-4 project, a user from the United Kingdom received training regarding retrieval steps used in the STRAT+ algorithm that retrieves atmospheric boundary layer heights from automatic lidar and ceilometer measurements. Results have been presented during a TOPROF COST action workshop in Dublin (Sept 2017).

SIRTA-5 project enabled two users, from Spain and to apply a method developed at SIRTA to study the hygroscopic growth of aerosols using attenuated backscatter signal measured by a ceilometer. Results were presented at ACTRIS-2 WP2 workshop in Delft (Nov 2017).

SIRTA-6 project enabled a user from the Netherland to evaluate LES runs of a continental fog event against detailed in-situ and remote sensing observations from SIRTA. Results will be submitted for publication (Wærsted et al. 2018 to be submitted).

SIRTA-7 project enabled two users from Romania to be trained about configuring a CHM15k ceilometer and the use of ceilometer measurements to study continental fog events. Following this training a new ceilometer was deployed at their home institution.

SIRTA-8 project enabled a returning user from Chile to participate in novel tests to improve our capacity to calibrate cloud radars. This project enabled the user to start a collaboration with a graduate student from TU-Delft (NL). Results combining TNA8 and TNA9 project will be presented at the ECAD conference in July 2018.

SIRTA TNA9 project enabled two users from the Netherland to test a cloud radar calibration method involving a calibration target flown by a drone, a novel method that could be very useful to calibrate vertically pointing cloud radars.

SIRTA-10 project enabled a user from the Belgium Meteorological services to develop his expertise further in the field of fog process understanding and fog nowcasting using automatic lidars and ceilometers.

SIRTA-11 enabled a user from the University of Granada (Spain) to be trained on using a Cloud Radar just purchased by the University. The Cloud radar performance was also evaluated.

SIRTA-12 enabled a student from Delft University (Netherland) to further train himself on the use of UAVs and targets to calibrate Cloud radars. The TNA allowed also a UAV pilot from Delft University to further his flight expertise to position cloud radar targets at precise locations.

SIRTA-13 enabled a Lidar expert from the company Raymetrics (Greece) to test a CDD camera to perform Lidar optical component alignments. His tests were performed on the SIRTA aerosol and cloud Raman Lidar (IPRAL).
SIRTA-1 project, TREBOL, was by high frequency acquisition (1 Hz) of data from Doppler and/or Elastic lidar to investigate boundary layer turbulence by using the particle backscatter coefficient profiles, as the aerosols act as tracers.

SIRTA-2 project enabled a user from Chile to be trained in cloud radar operation and calibration. The work achieved contributed to the Master of Science thesis of the user.

SIRTA-3 project enabled a user from Ireland to test a retrieval algorithm developed for cloud microphysical properties based on cloud radar and microwave radiometer measurements. Retrievals were compared to in-situ measurements of droplet size distributions. The results have been submitted for publication (Dupont et al. 2018, submitted).

In the SIRTA-4 project, a user from the United Kingdom received training regarding retrieval steps used in the STRAT+ algorithm that retrieves atmospheric boundary layer heights from automatic lidar and ceilometer measurements. Results have been presented during a TOPROF COST action workshop in Dublin (Sept 2017).

SIRTA-5 project enabled two users, from Spain and to apply a method developed at SIRTA to study the hygroscopic growth of aerosols using attenuated backscatter signal measured by a ceilometer. Results were presented at ACTRIS-2 WP2 workshop in Delft (Nov 2017).

SIRTA-6 project enabled a user from the Netherland to evaluate LES runs of a continental fog event against detailed in-situ and remote sensing observations from SIRTA. Results will be submitted for publication (Waersted et al. 2018 to be submitted).

SIRTA-7 project enabled two users from Romania to be trained about configuring a CHM15k ceilometer and the use of ceilometer measurements to study continental fog events. Following this training a new ceilometer was deployed at their home institution.

SIRTA-8 project enabled a returning user from Chile to participate in novel tests to improve our capacity to calibrate cloud radars. This project enabled the user to start a collaboration with a graduate student from TU-Delft (NL). Results combining TNA8 and TNA9 project will be presented at the ECAD conference in July 2018.

SIRTA TNA9 project enabled two users from the Netherland to test a cloud radar calibration method involving a calibration target flown by a drone, a novel method that could be very useful to calibrate vertically pointing cloud radars.

SIRTA-10 project enabled a user from the Belgium Meteorological services to develop his expertise further in the field of fog process understanding and fog nowcasting using automatic lidars and ceilometers.

SIRTA-11 enabled a user from the University of Granada (Spain) to be trained on using a Cloud Radar just purchased by the University. The Cloud radar performance was also evaluated.

SIRTA-12 enabled a student from Delft University (Netherland) to further train himself on the use of UAVs and targets to calibrate Cloud radars. The TNA allowed also a UAV pilot from Delft University to further his flight expertise to position cloud radar targets at precise locations.

SIRTA-13 enabled a Lidar expert from the company Raymetrics (Greece) to test a CDD camera to perform Lidar optical component alignments. His tests were performed on the SIRTA aerosol and cloud Raman Lidar (IPRAL).
SIRTA-14 and SIRTA-15 allowed an expert from IDAEA (Spain) and an expert from the University of Manchester (UK) to work on a method to better quantify organic nitrates using ACSM instruments in order to better understand the origin of organic nitrates.

SIRTA-16 allowed a doctoral student from the University of Texas (USA) to learn how to use automatic lidar and ceilometer measurements to retrieve the height of the boundary layer. This work will contribute to his PhD thesis where he studies the influence of ABL height and meteorology and Ozone concentrations in the city of El Paso, Texas.

SIRTA-17, SIRTA-18, SIRTA-19 are three projects that enabled several users to improve their knowledge on cloud radar calibration. These projects enabled a senior scientist from UKRI and a doctoral student from the University of Leeds (UK), a doctoral student from INOE (Romania) and a post-doctoral fellow from the University of Cologne (Germany), a doctoral student and a technician from Delft University (Netherlands) to work together on testing different techniques for cloud radar calibration, including reference targets, calibration transfer, UAVs and disdrometers.

These activities open new opportunities for TNA users to carry out research at SIRTA or to benefit from training opportunities.

## 5.4 Puy de Dôme Observatory, PUY (CNRS, UBP)

13 TNA projects were carried out at the Puy de Dome station for intercomparison campaigns at the PUY station in October 2016 and October 2018. The total access days provided is 228,5. The Puy de Dome site is a strategic place that provides the opportunity to sample within the planetary boundary layer and the free troposphere. The site is principally advected by westerly air masses (50%), but also from the southerly and easterly sectors and hence samples varied air mass. Locally the site is closed to public transport and hence is not influenced by local transport. Occasionally, in the case of easterly air masses, emissions from the nearby city of Clermont Ferrand can be advected to the site. The site is otherwise surrounded by fields and forested areas contributing to biogenic emissions being sampled at the site.

The Cloud microphysical probe inter-comparison campaign, took place at the PUY station from October 2nd to October 31st 2016, with 9 participating teams, among which 6 TNA projects. 16 probes were installed on the roof platform and 9 in the wind tunnel. 16 cloud events occurred and were characterized, corresponding to 193 hours of clouds between the 6th and the 26th of October (21 days of measurements).

INCePT (FMI, FI, PUY2) The Forward Scattering Spectrometer Probe (FSSP-100) and the Cloud, Aerosol and Precipitation Spectrometer probe (DMT-CAPS) probe were evaluated against each other and against the instrumentation of the partners contributing to cloud campaign in a natural cloud environment.

LWC-Comp (TROPOS, DE, PUY3): The Cloud Droplet Probe 2 with particle by particle feature (CDP-2), the Liquid Water Content Sensor 300 (LWC-300) and two Particle Volume Monitors 100A (PVM-100A) were evaluated. The campaign allowed to measure natural clouds in a wind tunnel with different cloud microphysical probes at the same time. So far, the campaign gave a better understanding of the new probes, CDP-2 and LWC-300, and showed how to handle these. It showed the operating limits of the LWC-300.

InterHOLIMO (IACS, CH, PUY4): The holographic imager HOLIMO and a Fog Monitor (DMT) were installed at the PUY station. In addition, a sonic anemometer measured the wind
SIRTA-14 and SIRTA-15 allowed an expert from IDAEA (Spain) and an expert from the University of Manchester (UK) to work on a method to better quantify organic nitrates using ACSM instruments in order to better understand the origin of organic nitrates.

SIRTA-16 allowed a doctoral student from the University of Texas (USA) to learn how to use automatic lidar and ceilometer measurements to retrieve the height of the boundary layer. This work will contribute to his PhD thesis where he studies the influence of ABL height and meteorology and Ozone concentrations in the city of El Paso, Texas.

SIRTA-17, SIRTA-18, SIRTA-19 are three projects that enabled several users to improve their knowledge on cloud radar calibration. These projects enabled a senior scientist from UKRI and a doctoral student from the University of Leeds (UK), a doctoral student from INOE (Romania) and a post-doctoral fellow from the University of Cologne (Germany), a doctoral student and a technician from Delft University (Netherlands) to work together on testing different techniques for cloud radar calibration, including reference targets, calibration transfer, UAVs and disdrometers.

These activities open new opportunities for TNA users to carry out research at SIRTA or to benefit from training opportunities.

## 5.4 Puy de Dôme Observatory, PUY (CNRS, UBP)

13 TNA projects were carried out at the Puy de Dome station for intercomparison campaigns at the PUY station in October 2016 and October 2018. The total access days provided is 228,5. The Puy de Dome site is a strategic place that provides the opportunity to sample within the planetary boundary layer and the free troposphere. The site is principally advected by westerly air masses (50%), but also from the southerly and easterly sectors and hence samples varied air mass. Locally the site is closed to public transport and hence is not influenced by local transport. Occasionally, in the case of easterly air masses, emissions from the nearby city of Clermont Ferrand can be advected to the site. The site is otherwise surrounded by fields and forested areas contributing to biogenic emissions being sampled at the site.

The Cloud microphysical probe inter-comparison campaign, took place at the PUY station from October 2nd to October 31st 2016, with 9 participating teams, among which 6 TNA projects. 16 probes were installed on the roof platform and 9 in the wind tunnel. 16 cloud events occurred and were characterized, corresponding to 193 hours of clouds between the 6th and the 26th of October (21 days of measurements).

INCePT (FMI, FI, PUY2) The Forward Scattering Spectrometer Probe (FSSP-100) and the Cloud, Aerosol and Precipitation Spectrometer probe (DMT-CAPS) probe were evaluated against each other and against the instrumentation of the partners contributing to cloud campaign in a natural cloud environment.

LWC-Comp (TROPOS, DE, PUY3): The Cloud Droplet Probe 2 with particle by particle feature (CDP-2), the Liquid Water Content Sensor 300 (LWC-300) and two Particle Volume Monitors 100A (PVM-100A) were evaluated. The campaign allowed to measure natural clouds in a wind tunnel with different cloud microphysical probes at the same time. So far, the campaign gave a better understanding of the new probes, CDP-2 and LWC-300, and showed how to handle these. It showed the operating limits of the LWC-300.

InterHOLIMO (IACS, CH, PUY4): The holographic imager HOLIMO and a Fog Monitor (DMT) were installed at the PUY station. In addition, a sonic anemometer measured the wind
direction to turn the Fog Monitor into the ambient wind field. The comparison of the concentration measurements and the liquid water content estimates from the new HOLIMO instrument will be used to quantify the uncertainties in the measurements as a function of the cloud properties and environmental conditions (wind speed/direction/temperature).

InterFOG (CNR-ISAC, IT, PUY5): CNR-ISAC provided a PVM system that is the fundamental measurement system for long-term liquid water content (LWC) observations at ground-based stations. An inter-comparison with similar (or alternative) measurement systems for LWC is therefore a prerequisite to assure high-quality observations for the long term record of fog at the SPC station.

ACTRIS2-FIDAS (PALSA, DE, PUY6): The Goal of the TNA access was to evaluate a new automatic instrumentation for cloud droplets real time analysis. This new instrument, called Fidas® 200 S, is based on TÜV certified analyzers used in long term air quality monitoring. This analyzer supplies a particle size distribution (mass and/or number) between 0.4 and 40 µm in 64 sizes channels. With two parallel running Fidas® 200 S the droplet distribution and density of clouds was measured. One Fidas® 200 S was running without an activated aerosol drying system and therefore measured the cloud droplets.

UTIPEX (U. Herthfordshire, PUY7): The Centre for Atmospheric and Instrumentation Research has recently developed a low-cost, miniature particle counter for use with disposable radiosondes, dropsondes, UAVs or in dense ground-based sensor networks. This Universal Cloud and Aerosol Sounding System (UCASS) is an open path optical particle counter, intended for deployment on ballon borne sounding systems, or as a dropsonde. The goal of the TNA was to evaluate the possibility of adapting this probe for a low price ground-base application, especially its robustness for long term measurements at ACTRIS stations.

The Puy de Dome ICe Nucleating Intercomparison Campaign (PICNIC), organised in October 2018, was an opportunity for a number of international researchers to share knowledge on aerosol ice nucleating particles. It was also a unique experiment with an unprecedented number of both direct and indirect measurement instruments for aerosol ice properties. A total of 12 research groups from seven different countries, participated in this exercise. Of these 12 research groups, 7 groups applied for and received transnational access (TNA) funds.

Luis Ladino and Caroline Ramirez from the National University of Mexico (PUY11 - MOUDI-DFT_PDD) spent almost three weeks at the Puy de Dome during the TNA-PICNIC experiment. During this time they installed their 10 stage filter collector to examine aerosol ice nucleating properties as a function of size. Using electron microscopy analysis of these filters, they are also able to link aerosol ice nucleating properties to aerosol particle morphology and chemistry. The data acquired during this exercise will be compared to similar measurements taken at other high altitude sites in Mexico Mt. Altomozi.

Duncan Axisa, a researcher from Droplet measurement technologies (DMT, Colorado, USA) worked alongside Martin Wolf from Massachusetts Institute of Technology (MIT), Boston to study the aerosol ice nucleating properties using the online Spectrometer for Ice nuclei (SPIN) instrument (PUY 10 & 13). This commercially available instrument is capable of attaining a wide temperature range, making it possible to study several ice formation pathways from immersion to deposition freezing. Martin Wolf will focus his analysis on how the deposition freezing of aerosol particles is dependent on their physical and chemical properties.
direction to turn the Fog Monitor into the ambient wind field. The comparison of the concentration measurements and the liquid water content estimates from the new HOLIMO instrument will be used to quantify the uncertainties in the measurements as a function of the cloud properties and environmental conditions (wind speed/direction/temperature).

InterFOG (CNR-ISAC, IT, PUY5): CNR-ISAC provided a PVM system that is the fundamental measurement system for long-term liquid water content (LWC) observations at ground-based stations. An inter-comparison with similar (or alternative) measurement systems for LWC is therefore a prerequisite to assure high-quality observations for the long term record of fog at the SPC station.

ACTRIS2-FIDAS (PALSA, DE, PUY6): The Goal of the TNA access was to evaluate a new automatic instrumentation for cloud droplets real time analysis. This new instrument, called Fidas® 200 S, is based on TÜV certified analyzers used in long term air quality monitoring. This analyzer supplies a particle size distribution (mass and/or number) between 0.4 and 40 µm in 64 sizes channels. With two parallel running Fidas® 200 S the droplet distribution and density of clouds was measured. One Fidas® 200 S was running without an activated aerosol drying system and therefore measured the cloud droplets.

UTIPEX (U. Herthfordshire, PUY7): The Centre for Atmospheric and Instrumentation Research has recently developed a low-cost, miniature particle counter for use with disposable radiosondes, dropsondes, UAVs or in dense ground-based sensor networks. This Universal Cloud and Aerosol Sounding System (UCASS) is an open path optical particle counter, intended for deployment on ballon borne sounding systems, or as a dropsonde. The goal of the TNA was to evaluate the possibility of adapting this probe for a low price ground-base application, especially its robustness for long term measurements at ACTRIS stations.

The Puy de Dome ICe Nucleating Intercomparison Campaign (PICNIC), organised in October 2018, was an opportunity for a number of international researchers to share knowledge on aerosol ice nucleating particles. It was also a unique experiment with an unprecedented number of both direct and indirect measurement instruments for aerosol ice properties. A total of 12 research groups from seven different countries, participated in this exercise. Of these 12 research groups, 7 groups applied for and received transnational access (TNA) funds.

Luis Ladino and Caroline Ramirez from the National University of Mexico (PUY11 - MOUDI-DFT_PDD) spent almost three weeks at the Puy de Dome during the TNA-PICNIC experiment. During this time they installed their 10 stage filter collector to examine aerosol ice nucleating properties as a function of size. Using electron microscopy analysis of these filters, they are also able to link aerosol ice nucleating properties to aerosol particle morphology and chemistry. The data acquired during this exercise will be compared to similar measurements taken at other high altitude sites in Mexico Mt. Altomozi.

Duncan Axisa, a researcher from Droplet measurement technologies (DMT, Colorado, USA) worked alongside Martin Wolf from Massachusetts Institute of Technology (MIT), Boston to study the aerosol ice nucleating properties using the online Spectrometer for Ice nuclei (SPIN) instrument (PUY 10 & 13). This commercially available instrument is capable of attaining a wide temperature range, making it possible to study several ice formation pathways from immersion to deposition freezing. Martin Wolf will focus his analysis on how the deposition freezing of aerosol particles is dependent on their physical and chemical properties.
Paul DeMott, (Colorado State University (CSU, USA), a well-known international figure in ice nucleation research benefited from ACTRIS TNA funds to carry out measurements at the Puy de Dome with both the online continuous flow diffusion chamber and the indirect measurements using the Ice spectrometer -data analyzed by Dr. Tom Hill (CSU, USA). During the PICNIC experiment, a research scientist Ezra Levin, and a masters student Kevin Barry, both from Paul DeMott's research group participated in the exercise. Their analysis includes a comparison of their two techniques and they have also provided their data for the general overview publications that are being prepared (PUY9).

Larissa Larcher, a postdoctoral research fellow from Ottmar Mohler's research group in Karlsruhe Institute of Technology in Germany, participated to the PICNIC exercise with the newly developed Portable ice nucleation expansion chamber (PINE). As a result of the unique features of this instrument, it was operated continuously over the month of October (PUY14). L. Larcher also collaborated closely with Mike Adams from University of Leeds (PUY15), who was also operating another PINE instrument. In collaboration with all participants, Larissa Larcher will make a detailed comparison on the online instruments operating during the PICNIC exercise. Another colleague from the Ottmar Mohler group, Barbara Bertozzi also participated in the intercomparison where she was collecting offline filter measurements

Stephanes Mertes and Conrad Jentzsch, in collaboration with Heike Wex, all from TROPOS laboratory in Liepzig Germany installed two types of indirect sampling apparatus during the PICNIC experiment, one of which is commonly used in aircraft studies (PUY12). The objective of using two different sampling sets was to do a series of tests to determine the reproducibility of their techniques over an extended sampling period.

The principle objectives of this exercise were to compare different methods and a great effort was made to ensure that all instruments were operating over similar sampling conditions. However thanks to the wide range of aerosol chemical and physical measurements installed at the Puy de Dome site we will also dedicate one part of this study to identifying the links between aerosol properties and their ability to become an ice nuclei. In parallel to this experiment, and in collaboration with a large number of European colleagues a number of filters samples were collected at 12 different ACTRIS sites, the objective of this side study were to compare IN conditions throughout Europe and also to put in place a series of standard operating procedures that can be used in various sampling sites for the study of aerosol ice nucleating properties.

## 5.5 Maïdo Observatory - Observatoire de Physique de l'Atmosphère à La Réunion, MAIDO-OPAR (CNRS, UR)

Within ACTRIS-2, WP9 framework, OSU-R has accommodated the scientific missions of seven international groups (Belgium, Finland, Germany, Greece, Switzerland, and USA) at the atmospheric Maïdo Observatory (accounting for 298 access days). The research topics encompass a large panel of sharing activities in studies for composition of air masses, aerosol characterization, and procedures to calibrate instrumentation, between the TNA-ACTRIS researchers and researchers and engineers at OSU-R/LACy (Laboratoire for Atmosphere and Cyclones, UMR 8105) and OSU-R/UMS 3365.

TNA activities led by DWD (Lindenberg, Germany), ETHZ (Zurich, Switzerland) and NOAA (Boulder, USA) at the Maïdo observatory have allowed to make significant progresses in bringing quality (QA/QC) in the radiosonding processes to establish water vapour vertical
Paul DeMott, (Colorado State University (CSU, USA), a well-known international figure in ice nucleation research benefited from ACTRIS TNA funds to carry out measurements at the Puy de Dome with both the online continuous flow diffusion chamber and the indirect measurements using the Ice spectrometer -data analyzed by Dr. Tom Hill (CSU, USA). During the PICNIC experiment, a research scientist Ezra Levin, and a masters student Kevin Barry, both from Paul DeMott's research group participated in the exercise. Their analysis includes a comparison of their two techniques and they have also provided their data for the general overview publications that are being prepared (PUY9).

Larissa Larcher, a postdoctoral research fellow from Ottmar Mohler's research group in Karlsruhe Institute of Technology in Germany, participated to the PICNIC exercise with the newly developed Portable ice nucleation expansion chamber (PINE). As a result of the unique features of this instrument, it was operated continuously over the month of October (PUY14). L. Larcher also collaborated closely with Mike Adams from University of Leeds (PUY15), who was also operating another PINE instrument. In collaboration with all participants, Larissa Larcher will make a detailed comparison on the online instruments operating during the PICNIC exercise. Another colleague from the Ottmar Mohler group, Barbara Bertozzi also participated in the intercomparison where she was collecting offline filter measurements

Stephanes Mertes and Conrad Jentzsch, in collaboration with Heike Wex, all from TROPOS laboratory in Liepzig Germany installed two types of indirect sampling apparatus during the PICNIC experiment, one of which is commonly used in aircraft studies (PUY12). The objective of using two different sampling sets was to do a series of tests to determine the reproducibility of their techniques over an extended sampling period.

The principle objectives of this exercise were to compare different methods and a great effort was made to ensure that all instruments were operating over similar sampling conditions. However thanks to the wide range of aerosol chemical and physical measurements installed at the Puy de Dome site we will also dedicate one part of this study to identifying the links between aerosol properties and their ability to become an ice nuclei. In parallel to this experiment, and in collaboration with a large number of European colleagues a number of filters samples were collected at 12 different ACTRIS sites, the objective of this side study were to compare IN conditions throughout Europe and also to put in place a series of standard operating procedures that can be used in various sampling sites for the study of aerosol ice nucleating properties.

## 5.5 Maïdo Observatory - Observatoire de Physique de l'Atmosphère à La Réunion, MAIDO-OPAR (CNRS, UR)

Within ACTRIS-2, WP9 framework, OSU-R has accommodated the scientific missions of seven international groups (Belgium, Finland, Germany, Greece, Switzerland, and USA) at the atmospheric Maïdo Observatory (accounting for 298 access days). The research topics encompass a large panel of sharing activities in studies for composition of air masses, aerosol characterization, and procedures to calibrate instrumentation, between the TNA-ACTRIS researchers and researchers and engineers at OSU-R/LACy (Laboratoire for Atmosphere and Cyclones, UMR 8105) and OSU-R/UMS 3365.

TNA activities led by DWD (Lindenberg, Germany), ETHZ (Zurich, Switzerland) and NOAA (Boulder, USA) at the Maïdo observatory have allowed to make significant progresses in bringing quality (QA/QC) in the radiosonding processes to establish water vapour vertical
profiles in the atmosphere according to the GRUAN (GCOS Reference Upper Air Network) principles. Collaborative research on the topic is ongoing and is focusing on the impact of water vapour transport processes in the Tropical Tropopause Layer. TNA activities led by IASB (Brussels, Belgium) and UHEL (University of Helsinski, Finland) at the Maïdo observatory initially planned to prepare the groundwork on the topic of atmosphere-biosphere exchanges processes have confirmed the interests to further study the complete cycle of aerosols emitted by the biosphere in their impact on the cloud microphysics in La Réunion. TNA activities have acted as a technology incubator to successfully mount the French national research project ANR BIO-Maïdo (https://anr.fr/Projet-ANR-18-CE01-0013) and an international project BELSPO OCTAVE (http://www.belspo.be/belspo/fedra/proj.asp?l=en&COD=BR/175/A2/OCTAVE). Collaborative research on the topic is ongoing.

TNA MORGANE-MAIDO (MAIDO1, May 2015): The goal of this project was to provide high-resolution balloon measurements of temperature and water vapour to complement existing instruments at the Maïdo observatory in the framework of the MORGANE (Maïdo ObservatoRy Gas and Aerosols NDACC Experiment) campaign. Suzanne Meier (DWD, Lindenberg, Germany) was invited to participate to the campaign. She was in charge of water vapour radio soundings with the CFH (Cryogenic Frost-point Hygrometer) sonde. She trained our local staff to operate the sondes, Stéphanie Evan (OSU-R/LACy) and Jean-Marc Metzger (OSU-R/UMS). CFH data are being used for validation of the water vapour lidar data. A draft paper is in preparation (Vérèmes et al.). The measurements are also used to characterize the vertical structure of the UTLS over the Indian Ocean.

TNA FTIR-Cal-LaReunion (MAIDO2, October 2015): This project aimed at calibrating the two IFS 125HR spectrometers in operation at Maïdo observatory and at La Reunion University with the help of a well-calibrated lightweight, portable, low-resolution spectrometer - EM27/SUN. The two IFS spectrometers are labelled in the NDACC and TCCON networks. Work is still in progress to validate the calibration methodology which has the advantage to reduce the procedures for such a remote observatory in the southern hemisphere.

TNA AEROMARINE (MAIDO3, March 2016): The goal of this project is i) to test innovative measurement techniques with a drone and miniaturized particle counter instrument (POPS), ii) to acquire datasets on marine aerosol distribution and atmospheric thermodynamic state to further our understanding on marine aerosols and marine boundary layer, iii) to estimate the exchange of aerosols between the MBL and free troposphere. This project is also envisioned as an international collaborative effort between NOAA (USA) and OSU-Reunion and LACy laboratory. By bringing in expertise from NOAA, it will help design new strategies at Maïdo Observatory on innovative measurement techniques for future monitoring of atmospheric composition. This TNA action has promoted an exchange of expertise on aerosol measurements between NOAA scientists and OSU-Réunion scientists. OSU-Réunion, LACy and NOAA/CSD will collaborate on pursuing POPS measurements at Reunion Island.

TNA MAIDO4 was not accepted by reviewers.

TNA MAIDO5, SHUTLS, May 2017: The title of the proposal is "Composition of the Southern Hemisphere Tropical UTLS". Visiting scientists were R. Dirksen (Meteorological Observatory Lindenberg, Deutscher Wetterdienst, Germany) and F. Wienhold (Institute for Atmospheric and Climate Sciences, ETH Zürich). The current project leverages on a collaborative effort to elevate the Maïdo Observatory to an essential observatory for monitoring the Southern Hemisphere Upper Troposphere Lower Stratosphere composition (water vapor, ozone, aerosols). By bringing in expertise from the Lindenberg GRUAN Lead Centre and ETH, the overall objective of the project is to support the long-
profiles in the atmosphere according to the GRUAN (GCOS Reference Upper Air Network) principles. Collaborative research on the topic is ongoing and is focusing on the impact of water vapour transport processes in the Tropical Tropopause Layer. TNA activities led by IASB (Brussels, Belgium) and UHEL (University of Helsinski, Finland) at the Maïdo observatory initially planned to prepare the groundwork on the topic of atmosphere-biosphere exchanges processes have confirmed the interests to further study the complete cycle of aerosols emitted by the biosphere in their impact on the cloud microphysics in La Réunion. TNA activities have acted as a technology incubator to successfully mount the French national research project ANR BIO-Maïdo (https://anr.fr/Projet-ANR-18-CE01-0013) and an international project BELSPO OCTAVE (http://www.belspo.be/belspo/fedra/proj.asp?l=en&COD=BR/175/A2/OCTAVE). Collaborative research on the topic is ongoing.

TNA MORGANE-MAIDO (MAIDO1, May 2015): The goal of this project was to provide high-resolution balloon measurements of temperature and water vapour to complement existing instruments at the Maïdo observatory in the framework of the MORGANE (Maïdo ObservatoRy Gas and Aerosols NDACC Experiment) campaign. Suzanne Meier (DWD, Lindenberg, Germany) was invited to participate to the campaign. She was in charge of water vapour radio soundings with the CFH (Cryogenic Frost-point Hygrometer) sonde. She trained our local staff to operate the sondes, Stéphanie Evan (OSU-R/LACy) and Jean-Marc Metzger (OSU-R/UMS). CFH data are being used for validation of the water vapour lidar data. A draft paper is in preparation (Vérèmes et al.). The measurements are also used to characterize the vertical structure of the UTLS over the Indian Ocean.

TNA FTIR-Cal-LaReunion (MAIDO2, October 2015): This project aimed at calibrating the two IFS 125HR spectrometers in operation at Maïdo observatory and at La Reunion University with the help of a well-calibrated lightweight, portable, low-resolution spectrometer - EM27/SUN. The two IFS spectrometers are labelled in the NDACC and TCCON networks. Work is still in progress to validate the calibration methodology which has the advantage to reduce the procedures for such a remote observatory in the southern hemisphere.

TNA AEROMARINE (MAIDO3, March 2016): The goal of this project is i) to test innovative measurement techniques with a drone and miniaturized particle counter instrument (POPS), ii) to acquire datasets on marine aerosol distribution and atmospheric thermodynamic state to further our understanding on marine aerosols and marine boundary layer, iii) to estimate the exchange of aerosols between the MBL and free troposphere. This project is also envisioned as an international collaborative effort between NOAA (USA) and OSU-Reunion and LACy laboratory. By bringing in expertise from NOAA, it will help design new strategies at Maïdo Observatory on innovative measurement techniques for future monitoring of atmospheric composition. This TNA action has promoted an exchange of expertise on aerosol measurements between NOAA scientists and OSU-Réunion scientists. OSU-Réunion, LACy and NOAA/CSD will collaborate on pursuing POPS measurements at Reunion Island.

TNA MAIDO4 was not accepted by reviewers.

TNA MAIDO5, SHUTLS, May 2017: The title of the proposal is "Composition of the Southern Hemisphere Tropical UTLS". Visiting scientists were R. Dirksen (Meteorological Observatory Lindenberg, Deutscher Wetterdienst, Germany) and F. Wienhold (Institute for Atmospheric and Climate Sciences, ETH Zürich). The current project leverages on a collaborative effort to elevate the Maïdo Observatory to an essential observatory for monitoring the Southern Hemisphere Upper Troposphere Lower Stratosphere composition (water vapor, ozone, aerosols). By bringing in expertise from the Lindenberg GRUAN Lead Centre and ETH, the overall objective of the project is to support the long-
term development of a balloon sonde program in Reunion Island for the monitoring of atmospheric
composition over the tropical Southern Hemisphere.

TNA MAIDO6, IAMBIO, May 2017: The title of the proposal is "Identification of air masses arriving over Maïdo observatory with emphasis on biomass burning particles using aerosol and ozone lidar techniques and implications for climate change". Visiting scientist was S.C. Richardson (National Technical University of Athens, Greece). The goal for this graduate student was to be trained for the acquisition and treatment of lidar data at the Maïdo observatory and to build collaborations between scientists at NTU (Greece) and scientists at LACy (Laboratoire de l'Atmosphère et des Cyclones, Université de La Réunion).

TNA MAIDO7, OCTAVE/ISM, October 2017: The title of the proposal is "Oxygenated organic Compounds in the Tropical Atmosphere: Variability and atmosphere-biosphere Exchanges / In Situ Measurements". Visiting scientists were C. Amelyinck, N. Schoon, S. De Pauw (Royal Belgian Institute for Space Aeronomy, Brussels, Belgium). The OCTAVE project, aims to provide an improved assessment of the budget and role of oxygenated volatile organic compounds in tropical regions, and especially over oceans, relying on an integrated approach combining in situ measurements, satellite retrievals and global modelling. The general project is co-financed by the Belgian Federal Science Policy Office in the framework of the BRAIN.be program (http://octave.aeronomie.be). The goal of the TNA was to install the in-situ instrumentation (Mass Spectrometer) at the Maïdo Observatory. The project aims at obtaining a continuous series of measurements by the spectrometer at high temporal resolution for a period of two years. Collaborations are built with scientists at LACy (Laboratoire de l'Atmosphère et des Cyclones, Université de La Réunion for the scientific exploitation of the data.

TNA MAIDO8, OCTAVE, Feb May 2018: A field campaign was conducted in Maido-OPAR station during February-May 2018 and part of this time coincided with the OCTAVE (Oxygenated Compounds in the Tropical Atmosphere: Variability and Exchanges) intensive operation period. The motivation for the measurements was to infer the nucleating chemical vapours in the remote marine boundary layer (during day time), and in the free troposphere (during night time) at the 2.1 km altitude of the Maido-OPAR. For this purpose, a collection of mass spectrometric detection and nanoparticle size distribution characterization methods were utilized. The diverse emission profile of the site and the direct connection to free tropospheric air masses allowed to study various processes not easily accessible in most other locations, and lead to the following scientific objectives: (a) resolve the composition of in-situ nucleating vapours at the Maido-OPAR station (b) determine the potential role of halogen oxides in nanoparticle formation under free tropospheric conditions.

**5.6 Station for Measuring Ecosystem – Atmosphere Relations II, SMR (UHEL)**

SMR TNA access illustrated the large applicability of the SMR station for multidisciplinary research and also the wide variety of science that is part of our ACTRIS activities. Six TNA projects (454 access days, more than 3 times the planned number of access days) have been carried out at the station:

TNA BVOC-NPF (SMR-1, 46 access days) included detailed trace gas measurements (A Hansel, Innsbruck, Austria) with their new PTR3 mass spectrometer. This provided novel insights into the interplay between the volatile organic compounds emitted by the biosphere and atmospheric processes, such as formation of nanoparticles.
term development of a balloon sonde program in Reunion Island for the monitoring of atmospheric
composition over the tropical Southern Hemisphere.

TNA MAIDO6, IAMBIO, May 2017: The title of the proposal is "Identification of air masses arriving over Maïdo observatory with emphasis on biomass burning particles using aerosol and ozone lidar techniques and implications for climate change". Visiting scientist was S.C. Richardson (National Technical University of Athens, Greece). The goal for this graduate student was to be trained for the acquisition and treatment of lidar data at the Maïdo observatory and to build collaborations between scientists at NTU (Greece) and scientists at LACy (Laboratoire de l'Atmosphère et des Cyclones, Université de La Réunion).

TNA MAIDO7, OCTAVE/ISM, October 2017: The title of the proposal is "Oxygenated organic Compounds in the Tropical Atmosphere: Variability and atmosphere-biosphere Exchanges / In Situ Measurements". Visiting scientists were C. Amelyinck, N. Schoon, S. De Pauw (Royal Belgian Institute for Space Aeronomy, Brussels, Belgium). The OCTAVE project, aims to provide an improved assessment of the budget and role of oxygenated volatile organic compounds in tropical regions, and especially over oceans, relying on an integrated approach combining in situ measurements, satellite retrievals and global modelling. The general project is co-financed by the Belgian Federal Science Policy Office in the framework of the BRAIN.be program (http://octave.aeronomie.be). The goal of the TNA was to install the in-situ instrumentation (Mass Spectrometer) at the Maïdo Observatory. The project aims at obtaining a continuous series of measurements by the spectrometer at high temporal resolution for a period of two years. Collaborations are built with scientists at LACy (Laboratoire de l'Atmosphère et des Cyclones, Université de La Réunion for the scientific exploitation of the data.

TNA MAIDO8, OCTAVE, Feb May 2018: A field campaign was conducted in Maido-OPAR station during February-May 2018 and part of this time coincided with the OCTAVE (Oxygenated Compounds in the Tropical Atmosphere: Variability and Exchanges) intensive operation period. The motivation for the measurements was to infer the nucleating chemical vapours in the remote marine boundary layer (during day time), and in the free troposphere (during night time) at the 2.1 km altitude of the Maido-OPAR. For this purpose, a collection of mass spectrometric detection and nanoparticle size distribution characterization methods were utilized. The diverse emission profile of the site and the direct connection to free tropospheric air masses allowed to study various processes not easily accessible in most other locations, and lead to the following scientific objectives: (a) resolve the composition of in-situ nucleating vapours at the Maido-OPAR station (b) determine the potential role of halogen oxides in nanoparticle formation under free tropospheric conditions.

**5.6 Station for Measuring Ecosystem – Atmosphere Relations II, SMR (UHEL)**

SMR TNA access illustrated the large applicability of the SMR station for multidisciplinary research and also the wide variety of science that is part of our ACTRIS activities. Six TNA projects (454 access days, more than 3 times the planned number of access days) have been carried out at the station:

TNA BVOC-NPF (SMR-1, 46 access days) included detailed trace gas measurements (A Hansel, Innsbruck, Austria) with their new PTR3 mass spectrometer. This provided novel insights into the interplay between the volatile organic compounds emitted by the biosphere and atmospheric processes, such as formation of nanoparticles.
TNA HCCNP (SMR2- 25 access days) by Z. Wang, MPI performed measurements on hygroscopicity of these nanoparticles providing new data on their chemical composition with indirect methods.

TNA BORCOS (SMR-3, 18 access days), K. Maseyk, UK connected the biosphere-atmosphere interactions by looking at carbonylsulfide fluxes (COS) in the boreal environment. The hypothesis is that the COS flux is an independent measure of photosynthesis and the measurements during this TNA enabled us to probe into the ecosystem scale photosynthesis, which we can connect to the emissions of volatile compounds and aerosol formation and growth.

TNA SMR-4 was withdrawn by the user.

During the Hyytiälä Ice Nucleation Experiment 2018 (HyICE-2018) first comprehensive and long-term measurements of both aerosol properties and INP concentrations at the Hyytiälä Forestry Field Station, Finland, have been performed. The major goals of the campaign, led by the University of Helsinki, were (1) to measure the variability of both the total amounts and the temperature spectrum of INP concentrations, (2) to relate the INP results to aerosol variables like the number concentration and size distributions; this includes aerosol from local sources, e.g. formed during nucleation events or during and after precipitation, and aerosol from long-range transport, (3) to relate both aerosol and INP concentrations to meteorological conditions, (4) to relate the INP concentrations to ice observed in clouds around the field site with remote sensing (radar) and in situ (Unmanned Aerial Vehicles) methods, and (5) to use the results as input to cloud modelling in order to improve the understanding of primary ice formation in clouds, and to test and compare newly developed instruments for INP measurements. Three TNA projects were performed during this campaign.

KIT (SMR-5, 191 access days) contributed to HyICE-2018 using INSEKT (Ice Nucleation SpEctrometer of the Karlsruhe Institute of Technology) and the newly developed instruments PINE (Portable Ice Nucleation Experiment) for INP measurement. INSEKT makes use of aerosols sampled over longer time periods of hours to days. The aerosols are then washed off the filters and analyzed for the average INP concentrations of the sampled air in the temperature range from -5°C to -25°C. Aerosol samples have been taken at different locations in Hyytiälä (in the forest and from above canopy) and analyzed on site, so that the results were immediately available for comparison to other INP results and for guiding the ongoing campaign activities. Also, filters sampled during Cessna flights close to Hyytiälä Forestry Field Station allowed for very first investigations of INP concentrations in the boundary layer and free troposphere above a boreal forest. PINE is a new expansion type INP chamber developed together with the University of Leeds (SMR-7, 85 access days). PINE is constructed for fully automated operation and continuous INP measurements at high time resolution (minutes) and temperature from -5°C to -40°C. KIT and University of Leeds operated two PINE instruments during the HyICE campaign. Our first aim was the test and intercomparison of those new devices at the same location with other INP instruments under ambient sampling conditions. The second aim was to provide long-term INP data at selected activation temperatures with a shorter time resolution than the filter-based methods. The work carried out by the ETH (SMR-6, 89 access days) directly measured ambient INPs at several temperatures in condensation freezing mode. This was achieved by the implementation and utilisation of the technological advances to existing instrumentation intended to lower the limit of detection, allowing for accurate measurements of INPs at the temperature of ~-30°C. Additional instrumentation deployed during HyICE-2018 provided information about the biological components in aerosol particles,
TNA HCCNP (SMR2- 25 access days) by Z. Wang, MPI performed measurements on hygroscopicity of these nanoparticles providing new data on their chemical composition with indirect methods.

TNA BORCOS (SMR-3, 18 access days), K. Maseyk, UK connected the biosphere-atmosphere interactions by looking at carbonylsulfide fluxes (COS) in the boreal environment. The hypothesis is that the COS flux is an independent measure of photosynthesis and the measurements during this TNA enabled us to probe into the ecosystem scale photosynthesis, which we can connect to the emissions of volatile compounds and aerosol formation and growth.

TNA SMR-4 was withdrawn by the user.

During the Hyytiälä Ice Nucleation Experiment 2018 (HyICE-2018) first comprehensive and long-term measurements of both aerosol properties and INP concentrations at the Hyytiälä Forestry Field Station, Finland, have been performed. The major goals of the campaign, led by the University of Helsinki, were (1) to measure the variability of both the total amounts and the temperature spectrum of INP concentrations, (2) to relate the INP results to aerosol variables like the number concentration and size distributions; this includes aerosol from local sources, e.g. formed during nucleation events or during and after precipitation, and aerosol from long-range transport, (3) to relate both aerosol and INP concentrations to meteorological conditions, (4) to relate the INP concentrations to ice observed in clouds around the field site with remote sensing (radar) and in situ (Unmanned Aerial Vehicles) methods, and (5) to use the results as input to cloud modelling in order to improve the understanding of primary ice formation in clouds, and to test and compare newly developed instruments for INP measurements. Three TNA projects were performed during this campaign.

KIT (SMR-5, 191 access days) contributed to HyICE-2018 using INSEKT (Ice Nucleation SpEctrometer of the Karlsruhe Institute of Technology) and the newly developed instruments PINE (Portable Ice Nucleation Experiment) for INP measurement. INSEKT makes use of aerosols sampled over longer time periods of hours to days. The aerosols are then washed off the filters and analyzed for the average INP concentrations of the sampled air in the temperature range from -5°C to -25°C. Aerosol samples have been taken at different locations in Hyytiälä (in the forest and from above canopy) and analyzed on site, so that the results were immediately available for comparison to other INP results and for guiding the ongoing campaign activities. Also, filters sampled during Cessna flights close to Hyytiälä Forestry Field Station allowed for very first investigations of INP concentrations in the boundary layer and free troposphere above a boreal forest. PINE is a new expansion type INP chamber developed together with the University of Leeds (SMR-7, 85 access days). PINE is constructed for fully automated operation and continuous INP measurements at high time resolution (minutes) and temperature from -5°C to -40°C. KIT and University of Leeds operated two PINE instruments during the HyICE campaign. Our first aim was the test and intercomparison of those new devices at the same location with other INP instruments under ambient sampling conditions. The second aim was to provide long-term INP data at selected activation temperatures with a shorter time resolution than the filter-based methods. The work carried out by the ETH (SMR-6, 89 access days) directly measured ambient INPs at several temperatures in condensation freezing mode. This was achieved by the implementation and utilisation of the technological advances to existing instrumentation intended to lower the limit of detection, allowing for accurate measurements of INPs at the temperature of ~-30°C. Additional instrumentation deployed during HyICE-2018 provided information about the biological components in aerosol particles,
chemical composition of both gas and particle constituents in the atmosphere, as well as relevant cloud properties. These were supplemented by an amass of gas, particle and meteorological instrumentation available at the site. The projected outcomes will improve the IN parameterisations from field and lab studies based on the new data in order to reliably use them to predict atmospheric INP concentrations.

## 5.7 Pallas-Sodankylä Global Atmospheric Watch Station, PAL (FMI)

The station welcomed 6 TNA and provided 79,5 access days throughout the ACTRIS-2 project.

1) During the first reporting period, FMI hosted the TNA project ACITIC of PI Jaroslav Schwarz and his PhD student Petr Vodička: Aerosol-Cloud Interactions and their Impact on Arctic Climate as part of the Pallas Cloud Campaign, PaCE 2015, Finland (13.5 access days were provided). For this study, two months of EC/OC data, from 1st October to 1st December 2015, were taken by two EC/OC semi-online devices. Measurements covered 96% of the campaign period. The aim of the TNA was to study an earlier unexpected discrepancy of a factor of five between equivalent BC (eBC) measured by optical methods multi-angle absorption photometer (MAAP) and aethalometer and refractive BC measured by Single Particle Soot Photometer (SP2) by comparing the EC and OC measurements with results from other instruments. A comparison of the equivalent black carbon (eBC) results from aethalometer and MAAP one can determine the relevance of obtained EC measurements. Applicable EC and OC data will be used for an analysis of impact of these aerosols on Arctic climate.

During the 7th Pallas Cloud Experiment combined in-situ and remote-sensing observations to provide the best basis for process-level research on cloud-atmosphere interaction. We utilized combination of several research approaches: existing long-term continuous ground-based observations with in-situ sensors (Sammaltunturi station), airborne in-situ measurements (several remotely piloted aircraft systems and meteorological balloons), ground-based remote-sensing (lidars, ceilometers and cloud radar) and satellite retrievals. The pristine environment of Pallas area is characterised by very low aerosol load and optically thin clouds thus making vertical profiling (both in-situ and remote-sensing) very challenging. Intensive part of the campaign took place from September 8th to October 6th, during this period several groups visited Pallas. Since each group uses different instrumentation for in-situ measurements of aerosol and cloud properties aimed to have all groups in the air at the same time to maximize data overlap. During the campaign the airspace (PALLAS-EFD431) was reserved around Sammaltunturi station with radius of 6 km and ceiling at 2 km a.s.l. One of the special focus areas of the campaign was super-cooled liquid (SCL) water clouds. SCL water has significant influence to cloud radiative properties, precipitation through ice formation, and they create icing (e.g. wind turbines and air traffic). Forecasting and monitoring of the SCL layers is currently challenging and limited by measurement methods. Experiences from 6th PaCE suggest that combination of different scales of observations serve as best basis for investigating SCL properties and influence, and develop data retrieval methods. The following projects were conducted during PaCE 2017.

2) PAC-UAV-PaCE2017, Energy, Environment and Water Research Center (EEWRC), The Cyprus Institute: With the use of the UAVs, we obtained vertical profiles of particle size distributions within and above the boundary layer, as well as provided data from one or more altitudes separately. The flight path were designed to cover interesting areas and altitudes.
chemical composition of both gas and particle constituents in the atmosphere, as well as relevant cloud properties. These were supplemented by an amass of gas, particle and meteorological instrumentation available at the site. The projected outcomes will improve the IN parameterisations from field and lab studies based on the new data in order to reliably use them to predict atmospheric INP concentrations.

## 5.7 Pallas-Sodankylä Global Atmospheric Watch Station, PAL (FMI)

The station welcomed 6 TNA and provided 79,5 access days throughout the ACTRIS-2 project.

1) During the first reporting period, FMI hosted the TNA project ACITIC of PI Jaroslav Schwarz and his PhD student Petr Vodička: Aerosol-Cloud Interactions and their Impact on Arctic Climate as part of the Pallas Cloud Campaign, PaCE 2015, Finland (13.5 access days were provided). For this study, two months of EC/OC data, from 1st October to 1st December 2015, were taken by two EC/OC semi-online devices. Measurements covered 96% of the campaign period. The aim of the TNA was to study an earlier unexpected discrepancy of a factor of five between equivalent BC (eBC) measured by optical methods multi-angle absorption photometer (MAAP) and aethalometer and refractive BC measured by Single Particle Soot Photometer (SP2) by comparing the EC and OC measurements with results from other instruments. A comparison of the equivalent black carbon (eBC) results from aethalometer and MAAP one can determine the relevance of obtained EC measurements. Applicable EC and OC data will be used for an analysis of impact of these aerosols on Arctic climate.

During the 7th Pallas Cloud Experiment combined in-situ and remote-sensing observations to provide the best basis for process-level research on cloud-atmosphere interaction. We utilized combination of several research approaches: existing long-term continuous ground-based observations with in-situ sensors (Sammaltunturi station), airborne in-situ measurements (several remotely piloted aircraft systems and meteorological balloons), ground-based remote-sensing (lidars, ceilometers and cloud radar) and satellite retrievals. The pristine environment of Pallas area is characterised by very low aerosol load and optically thin clouds thus making vertical profiling (both in-situ and remote-sensing) very challenging. Intensive part of the campaign took place from September 8th to October 6th, during this period several groups visited Pallas. Since each group uses different instrumentation for in-situ measurements of aerosol and cloud properties aimed to have all groups in the air at the same time to maximize data overlap. During the campaign the airspace (PALLAS-EFD431) was reserved around Sammaltunturi station with radius of 6 km and ceiling at 2 km a.s.l. One of the special focus areas of the campaign was super-cooled liquid (SCL) water clouds. SCL water has significant influence to cloud radiative properties, precipitation through ice formation, and they create icing (e.g. wind turbines and air traffic). Forecasting and monitoring of the SCL layers is currently challenging and limited by measurement methods. Experiences from 6th PaCE suggest that combination of different scales of observations serve as best basis for investigating SCL properties and influence, and develop data retrieval methods. The following projects were conducted during PaCE 2017.

2) PAC-UAV-PaCE2017, Energy, Environment and Water Research Center (EEWRC), The Cyprus Institute: With the use of the UAVs, we obtained vertical profiles of particle size distributions within and above the boundary layer, as well as provided data from one or more altitudes separately. The flight path were designed to cover interesting areas and altitudes.
3) TNA-MWR PaCE2017, University of Cologne: The HATPRO Microwave radiometry provided valuable information on the total water content of the clouds observed and thus ideally complement the other sensors at the site. This will allow to constrain the radar reflectivity profile for retrievals of the liquid water content profile.

4) VPPM-PaCE2017, Palas & Airlip: Palas GmbH together with Airlip Service GmbH & Co KG will provided a Fidas Fly 200 instrument and flight robot (HORUS 2.0 octocopter), respectively. Fidas Fly200 provided the continuous and simultaneous measurement of the PM-fractions PM1, PM2.5, PM4, PM10, as well as in addition the particle number concentration as well as the particle size distribution in 32 size classes per decade within the particle size range of 0.18 – 18 µm or 0.5 – 40 µm - and all this in an additional spatial dimension.

5) SINP-PaCE2107, Karlsruhe Institute of Technology: Aerosol filter samples for offline analysis of daily averaged INP temperature spectra were taken over the whole campaign period.

6) ACCD-PaCE2017, University of Reading: Vertical profiles of (a) backscatter from cloud droplets, (b) in cloud turbulence, (c) electrical charge within clouds, and (d) supercooled liquid water (SLW) content were measured during the campaign. This was achieved by the use of specially developed disposable research sensors which were flown alongside standard meteorological radiosonde balloons.

## 5.8 High Altitude Research Station Jungfraujoch, JFJ (PSI)

Overall, nine TNA projects were undertaken at the Jungfraujoch which accounts for 391,5 access days. Notably, eight TNA projects were performed on occasion of the CLACE2017 campaign (Cloud and Aerosol Characterization Experiment 2017) which took place in January and February 2017.

1) A TNA NUCLACE-2016 was performed at the Jungfraujoch (3 access days). F. Bianchi, University of Helsinki, installed a neutral cluster air ion spectrometer (NAIS, Airel Ltd.), provided by the University of Helsinki. This instrument is able to detect aerosols below 5 nm (0.8 nm - 45 nm mobility diameter for ions and 3 - 45 nm for neutral particles). The NAIS is an ion mobility spectrometer that measures the number size distribution of ions and total (charged and neutral) particles. As the instrument will stay at the Jungfraujoch for 2 years it is premature to present results at this stage, however, interesting differences between positively and negatively charged small ions have already been observed and will be further evaluated.

2) CLACE-INUIT 2017, 53.5 access days, by participants from the University of Manchester (UoM) made measurements of the Microphysical parameters of the Clouds enveloping the Sphinx laboratory on the Jungfraujoch (JFJ). A suite of state-of-the-art instruments (see instrument list below for description of instruments and acronyms) was deployed, mounted on a purpose built platform capable of automatically rotating and tilting the instruments directly into the ambient wind for un-perturbed cloud sampling. The following measurements of cloud microphysical properties were made throughout the period of the experiment using : - a 3V-CPI probe, to observe the cloud particle size distributions, particle habit (derived from particle images), and hence formation of ice particles in cloud and degree of cloud glaciation; - a CDP to observe the cloud droplet size distributions (within super-cooled and mixed phase clouds) (NB; the 3V-CPI and CDP both mounted on a tilting rotating wing to direct probes into wind)
3) TNA-MWR_PaCE2017, University of Cologne: The HATPRO Microwave radiometry provided valuable information on the total water content of the clouds observed and thus ideally complement the other sensors at the site. This will allow to constrain the radar reflectivity profile for retrievals of the liquid water content profile.

4) VPPM-PaCE2017, Palas & Airlip: Palas GmbH together with Airlip Service GmbH & Co KG will provided a Fidas Fly 200 instrument and flight robot (HORUS 2.0 octocopter), respectively. Fidas Fly200 provided the continuous and simultaneous measurement of the PM-fractions PM1, PM2.5, PM4, PM10, as well as in addition the particle number concentration as well as the particle size distribution in 32 size classes per decade within the particle size range of 0.18 – 18 µm or 0.5 – 40 µm - and all this in an additional spatial dimension.

5) SINP-PaCE2107, Karlsruhe Institute of Technology: Aerosol filter samples for offline analysis of daily averaged INP temperature spectra were taken over the whole campaign period.

6) ACCD-PaCE2017, University of Reading: Vertical profiles of (a) backscatter from cloud droplets, (b) in cloud turbulence, (c) electrical charge within clouds, and (d) supercooled liquid water (SLW) content were measured during the campaign. This was achieved by the use of specially developed disposable research sensors which were flown alongside standard meteorological radiosonde balloons.

## 5.8 High Altitude Research Station Jungfraujoch, JFJ (PSI)

Overall, nine TNA projects were undertaken at the Jungfraujoch which accounts for 391,5 access days. Notably, eight TNA projects were performed on occasion of the CLACE2017 campaign (Cloud and Aerosol Characterization Experiment 2017) which took place in January and February 2017.

1) A TNA NUCLACE-2016 was performed at the Jungfraujoch (3 access days). F. Bianchi, University of Helsinki, installed a neutral cluster air ion spectrometer (NAIS, Airel Ltd.), provided by the University of Helsinki. This instrument is able to detect aerosols below 5 nm (0.8 nm - 45 nm mobility diameter for ions and 3 - 45 nm for neutral particles). The NAIS is an ion mobility spectrometer that measures the number size distribution of ions and total (charged and neutral) particles. As the instrument will stay at the Jungfraujoch for 2 years it is premature to present results at this stage, however, interesting differences between positively and negatively charged small ions have already been observed and will be further evaluated.

2) CLACE-INUIT 2017, 53.5 access days, by participants from the University of Manchester (UoM) made measurements of the Microphysical parameters of the Clouds enveloping the Sphinx laboratory on the Jungfraujoch (JFJ). A suite of state-of-the-art instruments (see instrument list below for description of instruments and acronyms) was deployed, mounted on a purpose built platform capable of automatically rotating and tilting the instruments directly into the ambient wind for un-perturbed cloud sampling. The following measurements of cloud microphysical properties were made throughout the period of the experiment using : - a 3V-CPI probe, to observe the cloud particle size distributions, particle habit (derived from particle images), and hence formation of ice particles in cloud and degree of cloud glaciation; - a CDP to observe the cloud droplet size distributions (within super-cooled and mixed phase clouds) (NB; the 3V-CPI and CDP both mounted on a tilting rotating wing to direct probes into wind)
a fixed position heated ultrasonic anemometer - to measure the 3-D wind vector and automatically direct cloud probes into wind; a wing mounted heated ultrasonic anemometer - to attempt measurements of cloud particle (drop and ice crystal) fluxes; a fixed position PVM - to make bulk cloud water measurements (in super-cooled and mixed phase conditions); T and RH measurements - made in vicinity of cloud microphysics/dynamics measurements The measurements of the liquid and ice phase cloud particle size distributions are to be used to calculate the cloud liquid and ice phase water contents (the former was also be measured directly); Interpretation of the combined aerosol and cloud data set (available to all) will be undertaken to identify the important ice formation mechanisms acting within the clouds.

3) For the INUIT JFJ project 2017, 32 access days, total aerosol particles and IPRs were sampled in parallel with the use of a MINI cascade impactor. The IPRs were collected behind the Ice-selective inlet (Ice-CVI). A dilution system was built to have the possibility to sample total particles for a longer time to match the duration of Ice-CVI sampling. Several different instruments for characterisation of the composition and physical properties of total aerosol, interstitial aerosol and IN. Single particles will be characterised by electron microscope (size, morphology, mixing state and chemical composition) at TU Darmstadt.

4) For FRIDGE@CLACE2017, 36 access days, ice nucleus counter FRIDGE was set up in a laboratory of the Research Station. From January 25 to February 20, 2017 atmospheric aerosol samples were collected at the Sphinx Laboratory. Samples were collected by two independent methods from a joint total aerosol inlet as well as downstream of a counterflow virtual impactor. For analysis of immersion freezing INP aerosol particles were collected by filtration, using membrane filters. For analysis of deposition/condensation INP particles were collected by electrostatic precipitation onto Si-wafers. At least one sample of each type was collected per day. Both types of samples were analysed in FRIDGE. Immersion freezing INP were measured at 0°C - -30°C in aqueous extracts of the filters, using the drop freezing method of Vali (1971). Deposition freezing INP were analysed between -20°C and -30°C by growing ice on the Si substrates, followed by photography and counting of the ice crystals. It is assumed that one ice crystal represents one ice nucleus.

5) INUIT-2017-MPIC, 57 access days, included instruments provided by the MPIC group included: single particle mass spectrometer ALABAMA, the aerosol mass spectrometer C-TOF AMS and additional instrumentation as a particle counter (CPC), optical particle sizers (OPC), and a Multi Angle Absorption Photometer (MAAP). During the campaign five different inlet systems were operated. The ICE-CVI (TROPOS) and the ISI (PSI) inlet were installed to select freshly produced ice particles out of mixed-phase clouds. The ALABAMA was connected to the ICE-CVI or ISI every time clouds were present around the JFJ-station. The C-ToF-AMS was connected to the ICE-CVI during a few selected cloud events. Besides of the ice selective inlets a total inlet (provided by PSI) was used most of the time for measurements with ALABAMA

6) For CLACE 2017, 30 access days, INP abundance was measured using the Horizontal Ice Nucleation Chamber (HINC). The chamber was operated at 242K and relative humidity of 94% and 104% with respect to water, respectively. The generally low concentrations of INPs in the free-troposphere, were detected by applying the new portable particle concentrator upstream of HINC. A heated particle inlet was deployed from the rooftop of the station to the laboratory, where the concentrator and HINC was located. In addition to the measurements with HINC, several other INP and aerosol instruments, which were participating in the field project, could be attached downstream of the particle concentrator. Measurements were taken with the
a fixed position heated ultrasonic anemometer - to measure the 3-D wind vector and automatically direct cloud probes into wind; a wing mounted heated ultrasonic anemometer - to attempt measurements of cloud particle (drop and ice crystal) fluxes; a fixed position PVM - to make bulk cloud water measurements (in super-cooled and mixed phase conditions); T and RH measurements - made in vicinity of cloud microphysics/dynamics measurements The measurements of the liquid and ice phase cloud particle size distributions are to be used to calculate the cloud liquid and ice phase water contents (the former was also be measured directly); Interpretation of the combined aerosol and cloud data set (available to all) will be undertaken to identify the important ice formation mechanisms acting within the clouds.

3) For the INUIT JFJ project 2017, 32 access days, total aerosol particles and IPRs were sampled in parallel with the use of a MINI cascade impactor. The IPRs were collected behind the Ice-selective inlet (Ice-CVI). A dilution system was built to have the possibility to sample total particles for a longer time to match the duration of Ice-CVI sampling. Several different instruments for characterisation of the composition and physical properties of total aerosol, interstitial aerosol and IN. Single particles will be characterised by electron microscope (size, morphology, mixing state and chemical composition) at TU Darmstadt.

4) For FRIDGE@CLACE2017, 36 access days, ice nucleus counter FRIDGE was set up in a laboratory of the Research Station. From January 25 to February 20, 2017 atmospheric aerosol samples were collected at in the Sphinx Laboratory. Samples were collected by two independent methods from a joint total aerosol inlet as well as downstream of a counterflow virtual impactor. For analysis of immersion freezing INP aerosol particles were collected by filtration, using membrane filters. For analysis of deposition/condensation INP particles were collected by electrostatic precipitation onto Si-wafers. At least one sample of each type was collected per day. Both types of samples were analysed in FRIDGE. Immersion freezing INP were measured at 0°C - -30°C in aqueous extracts of the filters, using the drop freezing method of Vali (1971). Deposition freezing INP were analysed between -20°C and -30°C by growing ice on the Si substrates, followed by photography and counting of the ice crystals. It is assumed that one ice crystal represents one ice nucleus.

5) INUIT-2017-MPIC, 57 access days, included instruments provided by the MPIC group included: single particle mass spectrometer ALABAMA, the aerosol mass spectrometer C-TOF AMS and additional instrumentation as a particle counter (CPC), optical particle sizers (OPC), and a Multi Angle Absorption Photometer (MAAP). During the campaign five different inlet systems were operated. The ICE-CVI (TROPOS) and the ISI (PSI) inlet were installed to select freshly produced ice particles out of mixed-phase clouds. The ALABAMA was connected to the ICE-CVI or ISI every time clouds were present around the JFJ-station. The C-ToF-AMS was connected to the ICE-CVI during a few selected cloud events. Besides of the ice selective inlets a total inlet (provided by PSI) was used most of the time for measurements with ALABAMA

6) For CLACE 2017, 30 access days, INP abundance was measured using the Horizontal Ice Nucleation Chamber (HINC). The chamber was operated at 242K and relative humidity of 94% and 104% with respect to water, respectively. The generally low concentrations of INPs in the free-troposphere, were detected by applying the new portable particle concentrator upstream of HINC. A heated particle inlet was deployed from the rooftop of the station to the laboratory, where the concentrator and HINC was located. In addition to the measurements with HINC, several other INP and aerosol instruments, which were participating in the field project, could be attached downstream of the particle concentrator. Measurements were taken with the
laser ablation single particle aerosol mass spectrometer ALABAMA (Brands et al. 2011), a second aerosol mass spectrometer (AMS, both from the Max Planck Institute for Chemistry in Mainz), the ice nucleation chamber FINCH (Bundke et al. 2008), the deposition freezing experiment FRIDGE (both University of Frankfurt), a wideband integrated bioaerosol sensor (WIBS) and the Laser Ablation of Aerosol Particles Time of Flight Mass Spectrometer (Laaptof from KIT). Our measurements of INP concentrations are complemented by several cloud measurements, conducted by our collaborators during this field project.

7) For INUIT-CLACE-2017, 47 access days, to achieve the scientific objectives, a laser ablation single particle time of flight mass spectrometer (LAAPTOF, AeroMegt GmbH) was deployed on the Jungfraujoch station measuring single particle composition of aerosol particles or residual particles selected by the different aerosol inlets available: total (w/o particle concentrator), interstitial, Ice counter flow virtual impactor (ICE-CVI) or ice selective inlet (ISI). Furthermore, aerosol particles were collected by the KIT filter sampler setup connected to the total aerosol inlet via a vertical sampling line. With this setup, particles were collected on filters during day and night time with a frequency of two filters per day. In total 57 filters were collected covering the time period from January 24th to February 22th. After collection, the filters were stored at -20°C and at the end of the campaign they were transported back to KIT. There, the collected aerosol particles will be washed off and will be analysed for their ice nucleation behaviour with an immersion freezing method, which is similar to the Ice Spectrometer of the Colorado State University (Hiranuma et al., 2015). The aerosol mass spectrometer and the filter sampling system were installed, tested and calibrated at the Jungfraujoch in the week from January 16th to 20th, 2017 and were taken down on February 23rd, 2017. Depending on the meteorological conditions, measurements were performed sampling continuously or intermittently at the different inlets.

8) The FINCH_INUIT-JFJ 2017, 60 access days, with the fast ice nucleus chamber, FINCH. Was meant to determine the number concentration of INP under different temperature and humidity conditions, on line. Supersaturation in the chamber is reached by mixing the aerosol flow with another very cold flow (-50°C) and a moist flow. Particles enter the chamber and grow to crystals if they are ice-active. Below the chamber an optical particle counter (FINCH-OPC, self-built) detects the number and size of the grown particles (particle size is proportional to the intensity of the forward scattered light). Thus it can be derived how many of the available particles were ice active (so-called INP). Moreover the autofluorescence of the particles, which are excited with UV light, is detected - this gives information whether the INP contained biological material. During the INUIT-JFJ 2017 campaign we operated FINCH at three different inlets: - At a total inlet (operated by PSI) to sample interstitial and activated aerosol. This inlet was used for most time of the campaign. - At an Ice-CVI (counterflow virtual impactor, operated by TROPOS; Mertes et al., 2007) to sample ice particle residuals. This inlet was used only for a few hours because particle number concentrations were too low to allow reliable INP detection with FINCH. - At a total inlet with concentrator (operated by ETH Zürich) to sample a concentrated flow of interstitial and activated aerosol. This inlet was used during the last five days of the campaign. The chamber temperature in FINCH was kept to -25°C for most of the campaign whereas the saturation ratio with respect to ice (sice) was varied between 1.1 and 1.3 to cover the humidity range below and above water saturation. Approximately once per hour sampling was done through a zero-filter for ca. 10 min to obtain the level of background noise. FINCH was operated usually only during daytime since it is an instrument that needs intensive maintenance.
laser ablation single particle aerosol mass spectrometer ALABAMA (Brands et al. 2011), a second aerosol mass spectrometer (AMS, both from the Max Planck Institute for Chemistry in Mainz), the ice nucleation chamber FINCH (Bundke et al. 2008), the deposition freezing experiment FRIDGE (both University of Frankfurt), a wideband integrated bioaerosol sensor (WIBS) and the Laser Ablation of Aerosol Particles Time of Flight Mass Spectrometer (Laaptof from KIT). Our measurements of INP concentrations are complemented by several cloud measurements, conducted by our collaborators during this field project.

7) For INUIT-CLACE-2017, 47 access days, to achieve the scientific objectives, a laser ablation single particle time of flight mass spectrometer (LAAPTOF, AeroMegt GmbH) was deployed on the Jungfraujoch station measuring single particle composition of aerosol particles or residual particles selected by the different aerosol inlets available: total (w/o particle concentrator), interstitial, Ice counter flow virtual impactor (ICE-CVI) or ice selective inlet (ISI). Furthermore, aerosol particles were collected by the KIT filter sampler setup connected to the total aerosol inlet via a vertical sampling line. With this setup, particles were collected on filters during day and night time with a frequency of two filters per day. In total 57 filters were collected covering the time period from January 24th to February 22th. After collection, the filters were stored at -20°C and at the end of the campaign they were transported back to KIT. There, the collected aerosol particles will be washed off and will be analysed for their ice nucleation behaviour with an immersion freezing method, which is similar to the Ice Spectrometer of the Colorado State University (Hiranuma et al., 2015). The aerosol mass spectrometer and the filter sampling system were installed, tested and calibrated at the Jungfraujoch in the week from January 16th to 20th, 2017 and were taken down on February 23rd, 2017. Depending on the meteorological conditions, measurements were performed sampling continuously or intermittently at the different inlets.

8) The FINCH_INUIT-JFJ 2017, 60 access days, with the fast ice nucleus chamber, FINCH. Was meant to determine the number concentration of INP under different temperature and humidity conditions, on line. Supersaturation in the chamber is reached by mixing the aerosol flow with another very cold flow (-50°C) and a moist flow. Particles enter the chamber and grow to crystals if they are ice-active. Below the chamber an optical particle counter (FINCH-OPC, self-built) detects the number and size of the grown particles (particle size is proportional to the intensity of the forward scattered light). Thus it can be derived how many of the available particles were ice active (so-called INP). Moreover the autofluorescence of the particles, which are excited with UV light, is detected - this gives information whether the INP contained biological material. During the INUIT-JFJ 2017 campaign we operated FINCH at three different inlets: - At a total inlet (operated by PSI) to sample interstitial and activated aerosol. This inlet was used for most time of the campaign. - At an Ice-CVI (counterflow virtual impactor, operated by TROPOS; Mertes et al., 2007) to sample ice particle residuals. This inlet was used only for a few hours because particle number concentrations were too low to allow reliable INP detection with FINCH. - At a total inlet with concentrator (operated by ETH Zürich) to sample a concentrated flow of interstitial and activated aerosol. This inlet was used during the last five days of the campaign. The chamber temperature in FINCH was kept to -25°C for most of the campaign whereas the saturation ratio with respect to ice (sice) was varied between 1.1 and 1.3 to cover the humidity range below and above water saturation. Approximately once per hour sampling was done through a zero-filter for ca. 10 min to obtain the level of background noise. FINCH was operated usually only during daytime since it is an instrument that needs intensive maintenance.
9) For the project INUIT2-RP2-TROPOS, 73 access days, the high alpine research station Jungfraujoch allowed to sample ice particles in real atmospheric mixed-phased clouds and the aerosol characterization of their ice particle residuals (IPR), which are closely related to atmospheric relevant INP. Thus, the objectives were the physico-chemical characterization of IPR within natural mixed-phase clouds. The determination of the IPR properties required the coupling of the unique Ice-CVI, developed by TROPOS, with several aerosol state of the art instruments. The IPR number concentration and size distribution were measured by CPC, OPS and UHSAS. The IPR chemical composition and mixing state is obtained by single particle mass spectrometry and electron spectroscopy applied by the cooperation partners MPI Mainz and TU Darmstadt.

Overall, the number of TNA days at the JFJ was nearly a factor of 3 higher than planned, demonstrating the success of TNA at the Jungfraujoch.

## 5.9 Cabauw Experimental Site for Atmospheric Research, CESAR (KNMI, TNO, TUD, UU, ECN)

Six TNA projects have been carried out at CESAR, having provided 129 access days (RWD) to users.

**CESAR-1:** In September 2016, a large-scale field campaign was held at the Cabauw Experimental Site for Atmospheric Research: The Second Cabauw Intercomparison Campaign for Nitrogen Dioxide Measuring Instruments — CINDI-2. The number of participating groups was 34 and involved 42 instruments. To support the campaign goals, NO2 profiles were provided by NO2 sondes and lidar, as well as through in-situ observations using the Cabauw meteorological tower. Extensive aerosol information was gathered using Raman aerosol lidar as well as by in situ samplers. Several publications based on the campaign are in preparation. These will possibly be bundled in a special issue.

The TNA project CEILMAX (CESAR-2: Development of aerosol retrieval techniques from MAX-DOAS and lidar/ceilometer measurements) aimed at obtaining extensive data of the atmospheric composition and meteorological conditions for the diagnostic of the MAX-DOAS retrieval technique and to develop a new technique for the retrieval of aerosol optical properties by integrating MAX-DOAS and lidar/ceilometer observations.

In September 2017, Utrecht University organized the Proton-transfer-reaction mass-spectrometer (PTR-MS) Intercomparison campaign in CABauw during which 5 TNA projects were accommodated involving groups outside the ACTRIS consortium. Eleven PTR-MS instruments operated by European and US groups measured for two weeks the ambient air composition at the CESAR observatory near Cabauw. All instruments were subjected to new calibration procedures, developed at UU/IMAU, using a gas standard custom manufactured by the National Physics Laboratory (NPL), UK. PTR-MS technology recently underwent major innovations that boosted the sensitivity by 2-3 orders of magnitude. These new generation instruments detect organic species at extremely low mixing ratios of 100 parts per quadrillion (fmol/mol) with a really great performance: 10 seconds time resolution and a precision of ~10%! We were fortunate to attract this latest technology (only 2 instruments exist worldwide) as well as instruments that have served already for more than 10 years.

**CESAR-3:** PIP (Participation in PTR-MS intercomparison) contributed to the intercomparison with two brand-new types of PTR-MS instruments by University of Leicester.
9) For the project INUIT2-RP2-TROPOS, 73 access days, the high alpine research station Jungfraujoch allowed to sample ice particles in real atmospheric mixed-phased clouds and the aerosol characterization of their ice particle residuals (IPR), which are closely related to atmospheric relevant INP. Thus, the objectives were the physico-chemical characterization of IPR within natural mixed-phase clouds. The determination of the IPR properties required the coupling of the unique Ice-CVI, developed by TROPOS, with several aerosol state of the art instruments. The IPR number concentration and size distribution were measured by CPC, OPS and UHSAS. The IPR chemical composition and mixing state is obtained by single particle mass spectrometry and electron spectroscopy applied by the cooperation partners MPI Mainz and TU Darmstadt.

Overall, the number of TNA days at the JFJ was nearly a factor of 3 higher than planned, demonstrating the success of TNA at the Jungfraujoch.

## 5.9 Cabauw Experimental Site for Atmospheric Research, CESAR (KNMI, TNO, TUD, UU, ECN)

Six TNA projects have been carried out at CESAR, having provided 129 access days (RWD) to users.

**CESAR-1:** In September 2016, a large-scale field campaign was held at the Cabauw Experimental Site for Atmospheric Research: The Second Cabauw Intercomparison Campaign for Nitrogen Dioxide Measuring Instruments — CINDI-2. The number of participating groups was 34 and involved 42 instruments. To support the campaign goals, NO2 profiles were provided by NO2 sondes and lidar, as well as through in-situ observations using the Cabauw meteorological tower. Extensive aerosol information was gathered using Raman aerosol lidar as well as by in situ samplers. Several publications based on the campaign are in preparation. These will possibly be bundled in a special issue.

The TNA project CEILMAX (CESAR-2: Development of aerosol retrieval techniques from MAX-DOAS and lidar/ceilometer measurements) aimed at obtaining extensive data of the atmospheric composition and meteorological conditions for the diagnostic of the MAX-DOAS retrieval technique and to develop a new technique for the retrieval of aerosol optical properties by integrating MAX-DOAS and lidar/ceilometer observations.

In September 2017, Utrecht University organized the Proton-transfer-reaction mass-spectrometer (PTR-MS) Intercomparison campaign in CABauw during which 5 TNA projects were accommodated involving groups outside the ACTRIS consortium. Eleven PTR-MS instruments operated by European and US groups measured for two weeks the ambient air composition at the CESAR observatory near Cabauw. All instruments were subjected to new calibration procedures, developed at UU/IMAU, using a gas standard custom manufactured by the National Physics Laboratory (NPL), UK. PTR-MS technology recently underwent major innovations that boosted the sensitivity by 2-3 orders of magnitude. These new generation instruments detect organic species at extremely low mixing ratios of 100 parts per quadrillion (fmol/mol) with a really great performance: 10 seconds time resolution and a precision of ~10%! We were fortunate to attract this latest technology (only 2 instruments exist worldwide) as well as instruments that have served already for more than 10 years.

**CESAR-3:** PIP (Participation in PTR-MS intercomparison) contributed to the intercomparison with two brand-new types of PTR-MS instruments by University of Leicester.