A Diagnostic Study of the Impact of SEASAT Scatterometer Winds on Numerical Weather Prediction

N. B. Ingleby Meteorological Office, Bracknell, Berkshire, United Kingdom

Search for other papers by N. B. Ingleby in
Current site
Google Scholar
PubMed
Close
and
R. A. Bromley Meteorological Office, Bracknell, Berkshire, United Kingdom

Search for other papers by R. A. Bromley in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

With the launch of ERS-1, observations of the wind close to the sea surface are expected to become available in near real time. To assess the effect of this new form of meteorological data an operational numerical weather prediction, the impact of similar data, from the SEASAT-A scatterometer in 1978, has been studied in the numerical forecasting system of the U.K. Meteorological Office. Some modifications to the system were necessary before the SEASAT data were assimilated into the model.

The geographical distribution of the differences between the analyses in a control run (without SEASAT data) and a parallel run (including SEASAT data) showed the largest values in the Southern Hemisphere and in association with some disturbances in the tropics. Studies have been made of the influence of some of the internal features of the assimilation scheme, especially the vertical cutoff in the data selection and the vertical correlation function. Changes to the model's divergence and vorticity have also been investigated. Overall, the inclusion of the SEASAT data appears to have slightly improved the model analyses.

The differences between the two versions of the forecasts to 24 hours have been reviewed. Assessment is difficult because of the lack of corroborating data, but a beneficial effect has been found in the meridional wind, and a change in the ageostrophic flow has been detected.

Abstract

With the launch of ERS-1, observations of the wind close to the sea surface are expected to become available in near real time. To assess the effect of this new form of meteorological data an operational numerical weather prediction, the impact of similar data, from the SEASAT-A scatterometer in 1978, has been studied in the numerical forecasting system of the U.K. Meteorological Office. Some modifications to the system were necessary before the SEASAT data were assimilated into the model.

The geographical distribution of the differences between the analyses in a control run (without SEASAT data) and a parallel run (including SEASAT data) showed the largest values in the Southern Hemisphere and in association with some disturbances in the tropics. Studies have been made of the influence of some of the internal features of the assimilation scheme, especially the vertical cutoff in the data selection and the vertical correlation function. Changes to the model's divergence and vorticity have also been investigated. Overall, the inclusion of the SEASAT data appears to have slightly improved the model analyses.

The differences between the two versions of the forecasts to 24 hours have been reviewed. Assessment is difficult because of the lack of corroborating data, but a beneficial effect has been found in the meridional wind, and a change in the ageostrophic flow has been detected.

Save