1. ICWG: CGMS-43, 18-22 May 2015, Boulder, Colorado, USA. Coordination Group for Meteorological Satellites - CGMS Status report on the International Clouds Working Group (ICWG) Presented to CGMS-43 WGII/8

2. ICWG: CGMS-43, 18-22 May 2015, Boulder, Colorado, USA. Coordination Group for Meteorological Satellites - CGMS CGMS-43 ICWG-WP-01 STRUCTURE for International Clouds Working Group

3. ICWG: CGMS-43, 18-22 May 2015, Boulder, Colorado, USA. Coordination Group for Meteorological Satellites - CGMS Composition of the Working Group The WG is led by two co-chairs; The WG reports to CGMS through a rapporteur; Each CGMS space agency is represented by a nominated ICWG representative; Scientific and operational developers/users of cloud parameter retrievals are invited to contribute to the ICWG. This can be, for example by attending Biennial Workshops or participating in Topical Groups. International collaborations The ICWG shall establish close relationships with working groups in climate and meteorological community that use cloud parameter information (e.g. GEWEX). Association to CGMS scientific working groups The ICWG shall establish links with CGMS working groups associated to the activities of the ICWG. (associations with the IWWG and IPWG have been established).

4. ICWG: CGMS-43, 18-22 May 2015, Boulder, Colorado, USA. Coordination Group for Meteorological Satellites - CGMS Biennial Workshops The ICWG shall organize biennial scientific workshops, under the lead of the co- chairs. Informal Topical Groups The ICWG could form Topical Groups that serve as instrument to address the recommendations and key research questions identified at the biennial workshops. At the biennial workshops the Topical Group leads are invited to: report on progress since the last workshop; determine, in breakout sessions, their focal points and research questions; present, at the workshop’s plenary, their focal points and research questions present, at the workshop’s plenary, their recommendations to CGMS; review the workshop summary report and scientific meeting paper.

5. ICWG: CGMS-43, 18-22 May 2015, Boulder, Colorado, USA. Coordination Group for Meteorological Satellites - CGMS Topical GroupLead Use of Combined Sensors for Cloud RetrievalsBryan Baum Cloud ModelingPhil Watts Cloud Height for Wind ApplicationsAndrew Heidinger Cloud Retrievals over Snow and Ice SurfaceAndi Walther Severe Weather ApplicationsMike Pavolonis Validation SourcesPat Minnis Assessment of level-2 Passive Imager Cloud Parameter RetrievalsYong-Sang Choi Assessment of Retrieval UncertaintiesCaroline Poulssen Aggregation Methods for Climate ApplicationsNadia Smith Assessment of Cloud Parameter Data Records for Climate StudiesMartin Stengel Table: Current list of informal Topical Groups of the ICWG

6. ICWG: CGMS-43, 18-22 May 2015, Boulder, Colorado, USA. Coordination Group for Meteorological Satellites - CGMS Information Exchange The ICWG members are encouraged to exchange data and code with the aim to foster development of cloud retrieval algorithms and the generation data records for meteorological and climatologic applications. Training The ICWG shall promote the provision trainings by key-scientists, in the field of cloud retrievals and atmospheric radiative transfer, aligned with the biennial workshops. Website The ICWG shall establish a website, on which users find information on the workshops, access to common data records and tools, and information on the Topical Groups. The address of the web-site is http://www.icare.univ-lille1.fr/crew/index.php/Welcome_ICWGhttp://www.icare.univ-lille1.fr/crew/index.php/Welcome_ICWG. Thanks to ICARE, Université de Lille 1 - Sciences & Technologies

7. ICWG: CGMS-43, 18-22 May 2015, Boulder, Colorado, USA. Coordination Group for Meteorological Satellites - CGMS CGMS-43 ICWG-WP-02 SUMMARY REPORT International Clouds Working Group

8. ICWG: CGMS-43, 18-22 May 2015, Boulder, Colorado, USA. Coordination Group for Meteorological Satellites - CGMS The ICWG was formally known as the group in Cloud Retrieval Evaluation Workshop (CREW). The last workshop (CREW-4) was held on 4-7 March 2014, in Grainau, Germany with 69 participants in four sessions and eight subtopics: –Enhancing cloud parameter retrievals, assessing their associated errors –Improving their use in nowcasting and forecasting activities –Improving the characterization of long-term cloud property datasets.

9. ICWG: CGMS-43, 18-22 May 2015, Boulder, Colorado, USA. Coordination Group for Meteorological Satellites - CGMS The main recommendations of the CREW-4 were to: Improve cloud models used in retrievals to more accurately reflect reality, in particular ice crystal models, vertical in-homogeneity and multiple layers; Explore the potential of combining different types of observations in level-2 cloud retrievals methods; Explore the definition of a set of essential filtering rules in level-3 aggregation methods for different cloud parameters; Work towards the characterisation of uncertainties in level-2 and level-3 products; Explore production of multi-algorithm ensembles to assess uncertainty/sensitivity; Explore the production of long-term datasets aimed at stability and accurate assessment of product strengths and weaknesses; Use of common ancillary data and validation procedures for level-2 and level-3 data; Establish topical groups to make progress on a variety of outstanding issues, for example multi-layered clouds, severe weather applications, and aggregation methods.

10. ICWG: CGMS-43, 18-22 May 2015, Boulder, Colorado, USA. Coordination Group for Meteorological Satellites - CGMS Biennial workshop of the ICWG The 1 st biennial workshop of the ICWG will be held in Lille, France from 17 to 20 May 2016. The workshop will cover a wide range of topics concerning cloud parameter retrievals, its applications and related issues. Special attention will be given to the reports and recommendations of the Topical Groups. Key issues of the 1 st biennial workshop of the ICWG are: Cloud Modeling Cloud Parameter Retrievals from Combined Sensors Aggregation Methods for Climate Applications Assessment of Cloud Parameter Retrievals and their Uncertainty Estimates Cloud Parameters in Weather and Climate Applications

11. ICWG: CGMS-43, 18-22 May 2015, Boulder, Colorado, USA. Coordination Group for Meteorological Satellites - CGMS 17-20 May 2016, Lille, France, Europe Organized by Université de Lille 1 - Sciences & Technologies, France Financially supported by EUMETSAT