Session 1 – summary (1) Several new satellite data types have started to be assimilated in the last 4 years, all with positive impacts, including Metop-B (in addition to Metop-A) CrIS and ATMS on Suomi-NPP MW sounder in low-inclination orbit (Megha-Tropiques/SAPHIR) ISS Rapidscat – impact on TC track forecasts MWHS-2 183 and 118 GHz channels AMSR-2 In general, little evidence of “redundancy” or “saturation”. Assimilation experiments on COMS AMVs and CSRs are under way - Impact currently small - work in progress to improve it. Some data denial results: A. The “secondary” satellites in an orbital plane have BIG impact – their data are NOT redundant B. Removing NOAA p.m. orbit gives substantial impact. C. Removing polar RO has substantial impact (but not as much as B).

Session 1 – summary (2) Scientific progress on assimilation: Increasing impact from MW observations affected by cloud and precipitation. Main mechanism is via dynamical adjustment. Makes use of improved RT modelling for cloud. MWHS-2 FY-3B data used over land and over snow surfaces with some positive impacts. Positive impact of surface-sensitivity MW channels over land and over sea-ice. Use of retrieved MW emissivity improves results. Generally good impact for MW and IR radiances using inter-channel correlated observation errors. Temporally correlated error of GB-GNSS negligible beyond 1.5h Messages for space agencies: Scatterometer “virtual constellation” could be improved to give better space/time coverage. NWP centres rely on high-quality Level-1 data. Efforts still needed to improve quality, including via GSICS. NWP centres also rely on some high-quality Level-2 processing e.g. AMVs and their coverage and qc information

Session 1 – summary (3) Radio occultation (GNSS-RO): Direct impact of GNSS-RO on global NWP skill confirmed. Indirect impact also confirmed through impact on radiance bias correction. These data have potential for improving bias correction of radiosondes. COSMIC-1 system is degrading RO: FORMOSAT-7/COSMIC-2: A – 6 equatorial, B – 6 polar “NOAA is fully committed to COSMIC-2” Importance of extra-tropical RO data confirmed Expected impact of greatly enhanced future RO system demonstrated, with no saturation at ~100000 profiles per day.

Session 1 – summary (4) Compared to LEO, a GEO hyperspectral sounder gives higher temporal resolution - OSSE study shows this leads to improved TC track forecasts. 183 GHz multi-spectral GEO radiometer concept is being studied, focussing on improving the analysis of humidity. Study shows that it is very difficult with this instrument concept to make significant improvements. Effects of aerosols in NWP: WGNE case studies – 7(?) institutes participating Data assimilation – large uncertainties – too few high-quality data sets available   [Wise words from Ralph] [NWP centres are encouraged to perform impact studies on the effects of varying radiosonde launch times.]

Session 1 – summary (5) A question:   A question: USA GB-GNSS data are “going commercial” – issues for international dissemination? Comments to the workshop participants: Please use standard DA and ensemble DA terminology where possible (add ref.) ...