Session 1 – summary (1)
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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.
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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)
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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)
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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)
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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.
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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]
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[NWP centres are encouraged to perform impact studies on the effects
of varying radiosonde launch times.]
Session 1 – summary (5)
•
A question:
• USA GB-GNSS data are “going commercial” – issues for
international dissemination?
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Comments to the workshop participants:
• Please use standard DA and ensemble DA terminology where
possible (add ref.)
• ...