SST and NWP
SST and sea-ice can have an important role in determining the
behaviour of the overlying atmosphere. Consequently, NWP model systems need to be updated
regularly to ensure an accurate forecast. Daily analyses of both the SST and sea-ice extent and
concentration are required by many operational NWP system. SST often provides the forcing for
shower formation, affects the formation and subsequent evolution of tropical cyclones,
convection and thunderstorms, cyclogenesis itself, sea fog and sea breezes. As the SST it hanges
relatively slowly with respect to the atmosphere, it provides a good basis for
seasonal forecasting techniques.
SST is also used to help upper air forecasters at the World Aviation Forecst Centre (WAFC) monitor areas
more likely to develop Culmulonimbus activity which can produce a significant threat to aircraft.
Sea-ice also has a significant impact on the exchange
of energy between the atmosphere and the underlying surface, with a dramatic effect on
the surface temperature. It is difficult to retrieve SST from space in the marginal ice zone
due to the rapid development and retreat of sea ice depending on the season. Sea ice
can also affect satellite radiance retrievals and an incorrect distribution of sea-ice
may influence the model tropospheric state.
High resolution SST data products preserve SST gradients better
and have been shown to significantly alter the surface wind stress field. The figure to the left provides
a useful overview of SST observations from the AVHRR and AMSR-E satellite systems compared to Reynolds OIv2 and
the NCEP RTG_SST. Notice how well the near all-wether capability microwave SST observations
preserve the gradinet of SST compared to the analysis systems that rely on cloudy infrared and limited in situ sources.
Recently, the ECMWF NWP model has has be demonstated to have a sensitivity to the spatial
resolution of the SST fields used as the bottom boundary condition. A PDF of the paper available from the BAMS pages at
The GHRSST-PP is working together with mant National Meterological services
to ensure that SST data GHRSST-PP data products and services are tailored to requirements, provided on an
operational bases and provide an improved service in termns of data quality and access. Never before have so
many Satellite SST data set been avaialble to the community in this way. This frees up time to concentrate
on applying the data rather than gaining access to it in the first place.
An important element of the GHRSST-PP R/GTS is operational uptake of products. Tnhis can only take place if
NWP systemns are able to demonstrate a useful improvement to their forecast skill. This is a challenging and costly
area, but one that is a pre-requisite for the GHRSST-PP to be assessed by if it is to gain operational support.