7th International
EarthCARE Science Workshop- Report Bonn, Germany
11-13 June 2018

Table of Contents

Welcome and Introduction ....................................................................................................... 3
Session 1: Process Studies......................................................................................................... 4
Session 2: Observational Techniques ....................................................................................... 5
Session 3: Modelling ................................................................................................................. 8
Session 4: Radiation .................................................................................................................. 9
Posters ..................................................................................................................................... 11
Special Contributions .............................................................................................................. 11
Panel Discussion and Recommendations ............................................................................... 12

Acknowledgment
The workshop was jointly organized by ESA and DLR, in cooperation with JAXA, Max-PlanckInstitute for Meteorology and NiCT, with support of the Federal Ministry for Economic
Affairs and Energy of Germany.

Welcome and Introduction
Mr. H.-P. Lüttenberg welcomed the participants as representative of the management of
DLR. Mr. M. Borgeaud addressed the workshop on behalf of the ESA Earth Observation
Directorate management. Mr. T. Nakajima addressed the workshop on behalf of the JAXA
Earth Observation Research Center management.
The EarthCARE satellite was introduced and presented by the ESA EarthCARE ProjectManager, Mr. A. Lefebvre, who provided the project overview and programmatic status. The
Cloud Profiling Radar (CPR) onboard EarthCARE was introduced and its status presented by
the JAXA CPR Project Manager, Mr. E. Tomita. The EarthCARE satellite is the largest andmost complex satellite in the ESA Earth Explorer Programme and implemented incooperation with JAXA, that contributed on of the four scientific instruments, the CPR. The
other instrument are the Atmospheric Lidar (ATLID), the Multi-Spectral Imager (MSI) and theBroad-Band Radiometer (BBR). The satellite project was presently in Phase D.
Mr. A.J. Illingworth, University of Reading, and Mr. H. Okamoto, Kyushu University,presented an overview of the science background and expected contribution of the
EarthCARE mission. The geophysical data products that will be derived from the mission
were presented by Mr. D. Donovan, KNMI, and Ms. R. Oki, JAXA. The EarthCARE satellite willaddress how clouds and aerosols influence the incoming solar and reflected/emitted
terrestrial radiation. For this purpose, vertical profiles of ice and liquid water in clouds arebeing retrieved from the backscattered radar and lidar signals and vertical aerosol profiles
are determined from the lidar. Additional information is derived from the collocated imager
channels. These synergistically derived products, collocated with the nadir-pointing
geometry of the active instruments, are expanded into the across-track dimension using theswath information of the imager. Radiative transfer calculations are used to determine theradiative properties – heating rates, radiances and radiative fluxes – and assessed against
the observations of the Broad-Band-Radiometer. A complex advanced data retrieval system
exploiting the synergy of the four satellite instruments is being developed in Europe, Canada
and Japan, so that the scientific satellite data exploitation can commence soon after thesatellite has been launched.
The introductory session was followed by four dedicated sessions plus a Panel Discussion tosolicit the community feedback and recommendations.

Session 1: Process Studies
Chairs: R. Hogan, T. Nakajima

This session consisted of six talks that explored how the new observational capabilities ofEarthCARE will offer new insights into cloud, precipitation and aerosol processes. They all
highlighted the value of careful analysis of existing ground-based, airborne and satellite data
to better understand relevant meteorological and particle-scattering processes, which will
feed into a better interpretation of the new EarthCARE measurements when available. The
talks were followed by a discussion that covered a wider array of processes for which
EarthCARE will provide valuable data, such as convection, and ways in which EarthCARE
could be used to evaluate these processes in models.
•Warm clouds and rain formation: Keynote speaker T. Y. Nakajima described how the
combination of radar reflectivity from CloudSat and optical depth from MODIS
elucidated details of the formation of drizzle and rain from shallow clouds, and how“CFODD” diagrams could be used to evaluate models over land and ocean. Further
information was available from the effective-radius estimates by different nearinfrared wavelengths that are sensitive to different depths into the cloud.
EarthCARE’s Doppler capability, combined with geostationary imagery to provide
context, will add crucial extra information on updrafts and rain rates to better
understand cloud life cycles. J. Bühl described how cloud-top temperature provided
insights into the mechanisms of rain formation in different parts of the globe, andhow such analysis would be improved by the use of EarthCARE’s Doppler radar.

•

Mixed-phase clouds and snow: There is an urgent need to be able to makequantitative estimates of snowfall from space, but current algorithms, even thoseusing radar, are subject to large errors. Retrievals are made more complicated by thefact that snow typically falls from mixed-phase clouds, and the growth of snowflakes
may be by aggregation, deposition or riming. S. Mason and D. Moisseev showed how
the process of riming changes the radar reflectivity and Doppler velocity of snow,
and how riming was linked to the amount of supercooled water in the cloud. We
should therefore expect EarthCARE’s Doppler radar to significantly improve ourunderstanding of mixed-phase cloud and precipitation processes, as well as enabling
more accurate retrievals of snowfall rate.

•

Particle scattering properties: A key strength of EarthCARE will be the synergy of
instruments with different wavelengths on the same platform, but correctinterpretation of these measurements will require consistent and realistic particle
scattering models, particularly for ice and snow particles. L. Bugliaro reported
reasonable agreement between airborne radar-lidar retrievals of ice effective radiusand optical depth with solar-radiance retrievals, but larger differences compared toin-situ estimates. D. Moisseev highlighted the difference between radarbackscattering using different assumptions about snowflake morphology, alsoemphasizing the need to improve our understanding of scattering processes if
retrievals are to be reliable.

•Aerosols: A. Devasthale described the use of CALIPSO to understand the different
transport pathways of aerosol pollution into the Arctic. The HSRL capability of ATLID
will provide crucial new information on aerosol type and extinction coefficient, andtherefore be of interest for work, such as this, that is concerned with the interplay of
aerosols with weather and climate processes. Aerosol typing gives us a much better
handle on solar heating of the atmosphere, which is known to impact the evolutionof monsoon and other weather systems, but could also be used to evaluate chemicaltransport models. As mentioned by T. Y. Nakajima and J. Bühl, EarthCARE’s aerosol
measurements could also help us to better understand aerosol-cloud-precipitationinteractions.

The following oral presentation were given:
T. Nakajima, Key Note: Observing the cloud evolution process by using passive and active
spaceborne sensors such as EarthCARE, A-Train, and Himawari-8
L. Bugliaro, Interpretation of passive geostationary microphysical properties of ice clouds
using synergistic lidar-radar observations
S. Mason, The diagnosis of mixed phase cloud and estimates of aggregation and riming rates
from Doppler radar
D. Moisseev, Parametrization of falling snow microphysical and scattering properties for Wband radar retrievals
J. Bühl, Combined lidar and radar observations of the relationship between cloud-top
temperature, in-cloud dynamics and rain rate
A. Devasthale, How do temperature inversions control aerosol vertical distribution in the
Arctic during polar winter?

Session 2: Observational Techniques
Chairs: T. Nishizawa, U. Wandinger

The session on observational techniques dealt with a variety of synergistic instrumental
approaches and retrieval algorithms focusing on the exploitation of EarthCARE-likeobservations of clouds, aerosol and radiation. Two keynote speeches demonstrated the highpotential of active remote sensing from space for Earth system and climate research. Basedon CALIPSO/CloudSat results, D. Winker emphasized the importance of long-term synergistic
observations to identify, understand, and characterize cloud-climate feedbacks and tocharacterize key modes of climate variability. Only the combination of active sensors allows
us to observe vertical cloud structures, to characterize cloud-aerosol-precipitation processes
and to reveal the linkages between clouds and circulation. EarthCARE is critical in extending
and improving the long-term data records that have been started with CALIPSO andCloudSat. In her keynote presentation, H. Chepfer discussed in particular the importance oflong-term lidar observations of cloud top heights to constrain uncertainties on cloud
feedbacks, since the sign and amplitude of cloud feedbacks is a major source of uncertainty
for future climate prediction.
From the various contributions to this session and dedicated discussions thereafter, anumber of challenges and needs for further development and validation activities havebeen identified.
• Instrument continuation: EarthCARE provides the opportunity to continue long-term
measurements as started with CALIPSO/CloudSat, which are strongly needed to observe
trends in a changing climate (Winker et al., Chepfer et al.). A long-term parameter
continuity is required, and therefore we should already now plan beyond EarthCARE.
Observational gaps of more than 2 years without intercalibration between missions
must be avoided. Passive instruments may help to cover gaps. Polarimetry has a highpotential to improve the synergy of active and passive instruments in future.
• Shallow clouds: Changing atmospheric circulation patterns might become visible not
only in increasing top heights of deep convection, but also in changing shallow tropicalcumulus and stratocumulus clouds. Shallow cloud feedbacks depend on the balance of acompetition between weakening turbulent mixing and strengthening convective mixing.
Lidar monitoring of trends in the vertical structure of shallow clouds can constrain model
estimates of cloud changes starting after about 20 years of observation (Winker et al.,Chepfer et al.).
• Ice clouds: The radiative impact of ice clouds as well as the retrieval of ice cloudproperties strongly depend on the ice-crystal microphysics. Therefore, realistic
microphysical models and synergistic retrieval techniques, also considering more than
the four EarthCARE instruments, are required. Active sensors can help in developing
better imager algorithms, while geostationary imager data provide better global andtemporal context for the polar-orbiting instruments (Strandgren et al.). Radiative closurestudies using imager measurements of solar radiation can help constrain combined lidarradar retrievals of ice cloud properties (Ewald et al., Bozzo et al.). Retrieval schemes that
include lidar measurements also need to consider multiple-scattering effects properly(Okamoto et al.). New synergies by using radar and sub-millimeter Ice Cloud Imager (ICI)
are being exploited (Duncan et al.).
• Best-estimate retrievals and validation efforts: Synergistic approaches often rely on bestestimate retrievals (Bozzo et al., Ewald et al.). Such challenging methods require an indepth validation. Ground-based and airborne campaigns can help in acquiring datasetsfor algorithm evaluation and prepare for EarthCARE calibration and validation activities(Cazenave et al., Ewald et al., Groß et al.). The agencies should use opportunities
resulting from big field campaigns.
• Exploitation of the CPR Doppler capability: The Doppler capability of the EarthCARE CPR
will provide new insight into deep convection. However, space-borne Doppler radarobservations are challenging and require adequate consideration of the impact ofaliasing and non-uniform beam filling in the retrieval algorithms. An accuracy of better
than 1–2 m/s can be reached above the freezing level, if the pulse repetition frequency
is > 7000–7200 Hz (Kollias et al.).
• Aerosol retrievals: Aerosol radiative properties are type-dependent. Thus, proper
aerosol classification is required in order to calculate aerosol radiative effects. Lidar
measurements of particle depolarization ratio, lidar ratio and spectral•

extinction/backscatter coefficients, as well as synergistic lidar/imager retrievals ofspectral AOD, can be used for aerosol typing (Kudo et al.). Since the optical aerosol
properties strongly depend on wavelength, a harmonization between CALIPSO
observations at 532/1064 nm and EarthCARE observations at 355 nm is required forlong-term atmospheric studies.
Small-scale problems: Uncertainties in both cloud feedbacks and indirect aerosol forcing
involve processes acting on broken clouds at small spatial scales. Retrievals at best
possible horizontal and vertical resolution are needed to minimize sampling
uncertainties (Winker et al., Tornow et al.).

The following oral presentation were given:
D. Winker, Key Note: Lidar Observations as Climate Data Records
J. Strandgren, From collocated spaceborne lidar-imager observations to the geostationary
remote sensing of thin cirrus clouds and the anvil cirrus life cycle
Q. Cazenave, Comparison of airborne configurations in a radar-lidar retrieval technique as apreparation for EarthCARE
F. Eward, How Solar Reflectance can be used to improve a Variational Radar-Lidar Retrieval
for Ice Clouds
A. Bozzo, A synergistic "best estimate" retrieval of clouds, precipitation and aerosol for
EarthCARE, and its planned use in evaluating the ECMWF forecast model
H. Okamoto, Observations of cloud- and precipitation-microphysics and vertical motion
P. Kollias, The EarthCARE CPR Doppler measurements in Deep Convection: Challenges, PostProcessing and Science Applications
D. Duncan, Radar Sub-Millimeter Synergy
F. Tornow, EarthCARE’s Broadband Radiometer: Unforeseen Sampling Uncertainties
Associated with Cloudy Atmospheres
H. Chepfer, Key Note: The potential of a multi-decades space-borne lidar record to constrain
cloud feedbacks
S. Groß, EarthCARE-like measurements on the research aircraft HALO for preparation andvalidation studies
R. Kudo, Global 3D distributions of aerosol components retrieved by synergy of CALIOP and
MODIS

Session 3: Modelling
Chairs: J. Cole, K. Suzuki

Within this session presentations were given that touched on three aspects linking models
to space-based Earth observations in an effort of constraining cloud-relevant uncertainties
in global models. Cloud properties from CALIPSO are the basis of one such analysis which
partitioned contributions to longwave cloud feedback and evaluate this feedback in a single
global climate model (GCM). Contrary to previous studies, and the GCM, longwave cloud
feedback is found to be mainly due to changes in opaque cloud fraction changes rather thanchanges in cloud top height [Guelis et al., 2018].
Two presentations illustrated the utility of active and passive cloud observations forevaluation of simulated cloud microphysics. One presentation illustrated a methodology inwhich a combination of radar and imager observations was used to diagnose warm cloud
processes which were used to constrain their representations in a particular climate model.
Such process-oriented constraints, however, turned out to produce unrealistically large
aerosol indirect forcing, exposing compensating errors in the model that is amplified
through aerosol-cloud interplay [Jing and Suzuki, 2018]. The second presentation used
active and passive observations to evaluate mixed-phase clouds in their phase partitioning
simulated over the Southern Ocean in NICAM as a method to guide model development.
The single- and double-moment microphysics schemes in NICAM are evaluated against
satellite measurements to seek a way for improving the single-moment approach based on
more realistic double-moment results.
The final two presentations of the session summarized research results from ECMWF toassimilate space-based radar and lidar data into their forecast model in preparation for thelaunch of EarthCARE [Janisková and Fielding, 2018]. In order to incorporate the data into
the assimilation system several technical issues needed to be overcome. This included
developing a sufficiently fast and accurate operators, accounting for subgrid-scale cloudvariabililty and associating observation errors to the data. A side benefit of incorporating
the radar and lidar data into the assimilation system is that it is included in the automatic
data monitoring system, which can provide information about changes to the quality of thedata. With the data being assimilated into the ECMWF global weather prediction, model
tests were performed to assess the impact of the new observations. A positive impact was
found on short-term forecasts in the period August 2007 with a notable improvement intropical rainfall rates. These initial results of better forecasts suggest that future studies
may further improve and optimize the assimilation of EarthCARE cloud radar and lidar dataat ECMWF.
Reference:
Guelis, T. V., H. Chapfer, R. Guzman, M. Bonazzola, D. M. Winker, and V. Noel, 2018: Space
lidar observations constrain longwave cloud feedback. Sci. Rep., 8:16570,
doi:10.1038/s41598-34943-1.
Janisková, M. and M. Fielding, 2018: Operational Assimilation of Space-borne Radar andLidar Cloud Profile Observations for Numerical Weather Prediction (Report no. WP-6000:

Conclusions and recommendations). Retrieved 23 December 2018 fromhttps://www.ecmwf.int/en/elibrary/18500-operational-assimilation-space-borne-radar-andlidar-cloud-profile-observations.
Jing, X., and K. Suzuki, 2018: The impact of process-based warm rain constraints on theaerosol indirect effect. Geophys. Res. Lett., 45, 10729-10737, doi:10.1029/2018GL079956.
The following oral presentation were given:
H. Chepfer, Space Lidar observations constrain longwave cloud feedback
W. Roh, Evaluation of microphysics in mixed-phase clouds over the Southern Ocean in
NICAM using Joint simulator
K. Suzuki, Exploring a dichotomy between process-based constraint and energy-balance
requirement on aerosol-cloud interaction in climate modeling
M. Fielding, The ECMWF observation operator for direct 4D-Var assimilation of cloud radarreflectivity and lidar backscatter: developments and its use for monitoring
M. Janiskova, Experimental 4D-Var assimilation of space-borne cloud radar and lidar
observations in advance of EarthCARE

Session 4: Radiation
Chairs: K. Suzuki, N. Clerbaux

The “Radiation” session was introduced with a key note presentation about radiative
heating rate in the atmosphere by Dr. S. Kato from the CERES team (NASA Langley ResearchCenter). The session then pursued with 5 presentations encompassing a large panel ofstudies combining passive and active instruments. All those contributions confirmed theinterest of the EarthCARE’s payload to address several key scientific challenges linked to theeffect of radiation, either shortwave or longwave, in the climate system.
Atmospheric heating rate is a key element in the climate system. However, it is not directly
measured by satellite. Satellite broadband observations provide Top Of Atmosphere (TOA)
measurements acting as boundary conditions when retrieving the atmospheric heating rate
and/or the surface radiative budget. The retrieval involves necessarily a radiative transfer
modeling step over the (reconstructed) scene as observed from passive and active
instruments.
For a long time, atmospheric heating rates have been estimated from passive instruments
only. During the key note presentation, Dr. Kato, showed some limitations of the heating
rate climatology when obtained with only passive instruments (in the study MODIS cloudproperties). An advantage of using active instrument observations, from CloudSat and
CALIPSO, is the suppression of the heating and cooling peak “artifacts” that are modeled at
the altitudes of the cloud base and top that serve to define the cloud type. Another big

advantage of active instrument’s observations is the possibility to investigate radiative
effect of multi-layers cloudiness which is usually not possible with passive instrument
technologies. In a contribution, Dr. Devasthale (SMHI, Sweden) used 4 years of CALIPSO andCloudSat data to quantify the radiative effects of two-layer cloud systems. In general, highlevel thin clouds, like cirrus, are known to present a radiative heating effect due to thestrong longwave absorption and the limited shortwave effect. The study presented by Dr.
Devasthale showed that, in case of underlying optically thick cloud, the heating rate of thistype of cloud can be completely suppressed. The separation in altitude between the cloudlayers seems to play a major role: when this distance is less than 4 kilometers, the radiative
effect of cirrus turns from warming to cooling.
Radiation is also known to have some effect on the available eddy potential energy. Dr. Kato
showed that the longwave cooling at the top of the stratocumulus clouds contributes to thegeneration of eddy available potential energy. Similarly, the West-East contrast in
temperature between land and ocean is a factor contributing to the generation of potential
energy through the longwave heating rate. Many contributions recognize the importance ofaerosol in atmospheric heating rate, and the high variability of this key element of theclimate system.
The active instruments pairs like the CALIPSO+CloudSat (and the future EarthCARE
CPR+ATLID) provide however a limited spatial coverage and synergetic use of passive
instrument data is still highly profitable. Dr Feofilov (UPMC/LMD, France) showed how theactive instrument data can be combined with hyperspectral radiometers like IASI and AIRS.
The synergetic approach has been used to estimate IWC(z), the profile of the Ice Water
Content and the effect on the radiation budget at the TOA and the surface, as well as theatmospheric heating rate. Furthermore, it is stressed that the synergy with passive
instruments (in this case IASI in a morning orbit and AIRS in the afternoon) could be usefulto resolve the diurnal cycle of many important atmospheric processes.
For EarthCARE, the radiation profiles will be validated by comparison with the BBR TOA
radiances and fluxes products. Additional validations are also foreseen at the surface, bycomparison with pyranometer stations. An interesting contribution about the
spatiotemporal variability of the surface solar irradiance is presented by Dr. Deneke (Tropos,
Germany). A network of 99 pyranometers has been deployed to cover an area similar to the
future EarthCARE’s standard footprint (10km x 10km). Several months of data have beenacquired and provide several implications for closure assessment and also for EarthCARE
radiative profile validation.
Finally, the estimation of the reflected solar and emitted thermal fluxes from the 3-views
EarthCARE BBR radiometer is summarized by Dr. Domenech. Validation of the part of the
EarthCARE ground segment (namely the BMA-FLX processor) is presented and discussed.
The following oral presentation were given:
S. Kato, Key Note: Radiative heating rate computed with clouds derived from satellite based
active and passive sensors and their effects on generation of eddy available potential
energy.

A. Devasthale, The radiative impact of double layered cloud systems in the tropical upper
troposphere and lower stratosphere.
A. Feofilov, Radiative effects of clouds from the synergy of active and passive satellite
instruments: missing elements of puzzle.
F. Szczap, The McRALI Monte Carlo simulator to evaluate (HSR) lidar and (Doppler) radarobservables in 3D cloudy atmospheres: Application to EarthCARE mission.
H. Deneke, Spatiotemporal variability of solar irradiance at the surface: Implications forradiative closure at the surface.
C. Domenech, Solar and thermal radiative flux estimation for the EarthCARE BBR
instrument: Analysis of results.

Posters
The oral introductory session on the satellite and data products was supported by 30 poster
presentations. The posters provided details on the instruments and their level 1 data
products, the Ground Segment, the ESA end-to-end EarthCARE Simulator and the Japanese
Joint-Simulator, and in particular on the numerous geophysical data products and theirretrieval techniques.
The science sessions 1 to 4 were supported by 18 poster presentations, addressing
additional science preparatory activities, science activities in the EarthCARE context andexpected EarthCARE contributions.

Special Contributions
F. Seidel, NASA, presented the outcome of the NASA 2017 Decadal Survey with regards to
the recommendations on aerosol, cloud, convection and precipitation observables.
T. Tremas, CNES, discussed the support CNES is providing to the French research community
for science activities related to EarthCARE.
D. Lajas, ESA, introduced the EarthCARE Simulator, a tool developed by ESA for end-to-end
simulation of the EarthCARE performance, from the definition of an atmospheric scene,through radiative transfer modelling and Satellite instrument data processing to theretrieval of geophysical data products. The geophysical retrieval processors, developed by
the European and Canadian science groups are used by the simulator and are fullycompatible with both the simulator and the actual ESA Payload Data Ground Segment. The
EarthCARE Simulator is available to algorithm developers and will become available forscientific mission users.

Panel Discussion and Recommendations
Chairs: A.J. Illingworth, H. Okamoto

The importance to visualize temporal evolution of clouds was discussed. The participants
agreed that simultaneous observations of the Himawari-8 and EarthCARE are expected toreveal the evolution of cumulus clouds as demonstrated by Dr. Takashi Nakajima. Remaining
open question whether we can expect this analysis to convective clouds was also identified.
Applicability of closure study of cloud microphysics using radar/lidar and imager was
revisited and there exists a difficult case when ice cloud on top with water cloud below, as
demonstrated by Dr. Luca Bugliaro.
Importance of Doppler capability from EarthCARE on snow microphysics was discussed and
it is conclude that it will provide significant insights into snow and heavy snow with riming
and also will retrieve snow fall much better than previous space-borne sensors, as
demonstrated by Dr. Shannon Mason and Dr. Dmitri Moisseev.
Possibility to study interaction of aerosols and cloud/precipitation by EarthCARE for futureclimate prediction was discussed. As Dr. Johannes Buehl suggested, EarthCARE Doppler
information can disentangle the global picture of role of aerosols and in cloud vertical air
motion for rain formation. Dr. Manu Anna Thomas (presented by Dr. Abhay Devasthale)
successfully showed that temperature inversion controls aerosol vertical structure in Arctic
winter. Since aerosol layers are predominant below 1 km in Arctic, we concluded thatvertical resolution of 100 m of EarthCARE will play a critical role.
Constraints on climate models that will be achieved by EarthCARE was discussed. Dr. DavidWinker emphasized a strong need to have a continuous long-term data records of global
cloud vertical structure for contribution to a grand challenge: how fast will the Earth warm,
what will be the regional impacts and what is the coupling of clouds to atmosphericcirculation such as cloud-response to ENSO. Since cloud top heights from active and passive
sensors are different and also the NUBF effect should be corrected for the interpretation ofactive sensors signals, we need further studies. Combination of Geo-stationary satellite andEarthCARE was further discussed for evolution of anvils as presented by Dr. Johanne
Strandgen. In 2021, 1km resolution by MTG will be available in time for EarthCARE launch sothat there is a great chance to achieve same horizontal resolution of 1km between
EarthCARE and Geostationary satellite.
It was also discussed about the possible additional information when the two air-borne
HSRLs at 355nm and 532nm are available. To conclude the information content for the caseneeds to more flights with HSRLs and in situ and ground-based HSRL studies, as suggested
by Dr. Quitterie Cazenave.
Difficulties in retrieval of LWC in mixed phased clouds were discussed as presented by Dr.
Floran Ewald and was identified to be difficult and uncertainties leaded to 1.5W/m2 and to
be an observational gap. The topics needs more intensive studies.

Evaluation of ECMWF by EarthCARE data was discussed as demonstrated by Dr. Alessio
Bozzo. Accurate retrievals need to have a good knowledge to PIA of the bright band as also
for GPM. We concluded observations are needed.
Multiple scattering in space-borne lidar was discussed. As demonstrated by Dr. Hajime
Okamoto, the multiple-field of view multiple scattering lidar can penetrate optically thicker
clouds and to infer droplet size, to have such functions for future spaceborne lidar seems to
be a good idea.
Correction of satellite vertical motion, NUBF, Aliasing, Multiple scattering in CPR was
discussed. PRF of 7500Hz could correct all of the issues as Dr. Pavlos Kollias showed.
Synergy of sub-millimetre radiometer ICI onboard MetOp Second Generation that isscheduled to be launched in 2022, and EarthCARE was discussed. Ice water path fromsubmm radiometer will be an additional constrain for EarthCARE retrievals as suggested by
Dr. Dave Duncan.
We also discussed about the beam filling problem for the BBR in relation chopper speed.
Verification was required whether MSI can identify NUBF in BBR and correct.
Recommendations
1. HSRL-Doppler radar synergy. More simultaneous observations with high spectral
resolution lidar (HSRL) and Doppler radar from aircraft and ground based platforms areneeded to establish the accuracy and reliability of the retrieved products, in particular
the retrievals of optical depth from the HSRL.
2. Optical depth from the integrated ATLID backscatter from the ocean. Should this be a
new EarthCARE level 2 product to provide an additional constraint to the HSRL opticaldepth? It should be fairly easy to retrieve.
3. Optimum Doppler pulse repetition frequency. Examine the trade-off between operating
the Doppler radar at 7.2 -7.5 kHz for more accurate Doppler velocities or at lower
frequencies with less accuracy but increased maximum altitude
4. Doppler and microphysical retrievals. What Doppler accuracy and with what spatial
resolution is needed to improve the retrievals of snowfall, riming, drizzle rainfall and ice
cloud properties?
5. Radar attenuation by the (melting layer) bright band. 94GHz observations at the
ground could quantify this parameter. Currently, model values are used.
6. Aerosol extinction. A study is recommended for the components of the aerosol
extinction retrieval and how they depend on aerosol model assumptions.
7. Data assimilation (DA) studies. DA studies at ECMWF have shown positive impact ofCloudSat/Calipso data on forecasts (e.g. of tropical rainfall). Need to continue such work
to enable DA of EarthCARE data with latest model versions.
8. How is radiative heating linked to dynamics? Can only answer with a model because
latent heat is important. The SW aerosol heating profile depends on (uncertain) SSA.
Can we estimate SSA from lidar aerosol classification schemes? How do aerosol
extinction retrievals depend on aerosol model assumptions? The extra 7dB radar
sensitivity should lead to more accurate heating profiles of tropical high cirrus – but by
how much? How much ground clutter from the radar? Observations of cloud base atlower altitudes would improve accuracy of down-welling LW radiation estimates. Radarobservations closer to the ground would improve rainfall and snowfall estimates (seept. 4).
9. Radiative impact of thin (<300m) layers of super-cooled water at the top of stratiform
ice clouds. The global impact is significant, but observations are difficult; they attenuate
the lidar and do not fill the depth of the radar pulse.
10. Synergy with Himawari 8. Can we study the evolution of convective clouds?
11. LEVEL 3 products. Need to define these. Are they intended to inform NWP
parameterisation schemes and/or to adjust retrieval algorithms?
12. Continuation of CloudSat/Calipso data sets. To achieve continuity we need to consider
how to account for the different sampling of EarthCARE. Do we have the ability with
Atlid to detect climatological shifts of cloud top height to within a few metres per
decade?