Monitoring seasonal vegetation dynamics in the Sahel with ERS wind scatterometer data.

Eric MOUGIN		CESBIO (CNES-CNRS-UPS) 18 Ave. E. Belin 31401 TOULOUSE CEDEX FRANCE mougin@cesbio.cnes.fr
Pierre-Louis FRISON		CESBIO (CNES-CNRS-UPS) 18 Ave. E. Belin 31401 TOULOUSE CEDEX FRANCE frison@cesbio.cnes.fr
Pierre HIERNAUX		International Livestock Research Institute Centre Sahélien de l'ICRISAT, NIAMEY NIGER P.Hiernaux@cgnet.com

Abstract

Primarily designed for estimating wind speed and wind direction over sea surfaces, spaceborne scatterometers (WSC) have shown considerable potential for terrestrial applications as it was first highlighted with Seasat-A Scatterometer data (Kennett and Li, 1989), and more recently by several authors using ERS WSC data. Acquired since July 91, this latter represents the first and unique multi-temporal data set acquired by a coarse resolution active microwave instrument over continental surfaces. Using ERS data, we have shown that ^o measurements acquired at large incidence angles could be used for regional vegetation monitoring. Particularly, over arid regions, there is a strong sensitivity of ERS WSC response to changes in surface parameters, namely vegetation density and soil moisture content.

The objective of this paper is to investigate the capabilities of C-band ERS WSC data for monitoring inter-annual and seasonal development of herbaceous vegetation in the Sahel. To this end, we examine ^o d