Soil moisture anomaly

ASCAT is a radar which provides high-accuracy measurements of the ocean surface backscatter, which are used to retrieve ocean surface wind vectors. Scientists at EUMETSAT in Darmstadt, the EUMETSAT Ocean and Sea Ice Satellite Application Facility consortium, including the Royal Netherlands Meteorological Institute (KNMI), and in the ASCAT Science Advisory Group, are working closely to calibrate the instrument to tune the processing and to validate the products by monitoring natural targets, such as rain forests, sea ice and oceans. This allowed the dissemination of pre-calibrated ASCAT backscatter products three months after launch and ocean surface wind products four months after.

ASCAT wind data have been assimilated in the operational model of the European Centre for Medium-Range Weather Forecasts (ECMWF) since June 2007. Operational implementation is planned soon at the Met Office (UK), Météo-France and KNMI. In addition, ASCAT data have been important in monitoring the 2007 hurricane season and will be fully used in monitoring extra-tropical winter storms.

ASCAT backscatter and ocean surface wind products were formally declared pre-operational in early October 2007. Fully-calibrated ASCAT backscatter data is expected in early 2008, when several months of calibration data from specially designed ground transponders become available. This will allow scientists to study ocean surface winds in fronts, storms and hurricanes in unprecedented detail. Follow the links below for example images.

ASCAT wind vector (red)
Produced by the OSI SAF (KNMI) on April 1st, 2007.
The blue vectors originate from the HIRLAM Numerical Weather Prediction Model.

ASCAT wind barbs
Assimilated at ECMWF (fat: used; light: thinned) along with ECMWF surface-wind streamlines (grey: first-guess; solid:analysis) for two typhoons NARI (top-left) and WIPHA (bottom-right) on 00 UTC 15 September 2007.

Soil moisture index

EUMETSAT is cooperating closely with the Institute of Photogrammetry and Remote Sensing at the Vienna University of Technology to provide hydrologists with an ASCAT soil moisture index. Dissemination of the first ASCAT Level 2 soil moisture products is expected to begin in early 2008.

The image on this page shows the surface soil moisture anomaly situation over parts of South America and Africa for the period between 15 and 21 March 2007, derived from ASCAT data in combination with an ERS-1/2 long-term scattering parameter database. The blue areas are wetter than the 1992-2000 average for that period of the year, while the red areas are dryer. Areas where no soil moisture can be retrieved (tropical forest, etc.) or where soil moisture is meaningless (because of snow cover climatology for the period) are masked in grey. Severe wet conditions are visible in northeastern Argentina and Uruguay, caused by one of the wettest rainy periods in the last 100 years, forcing thousands to evacuate and devastating significant amounts of farmland. On the other extreme, several months without rain and record-high temperatures caused extensive droughts in southern Africa.

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