Arabian sea surface winds and ocean transports determined from ERS‐1 scatterometer

Abstract

Satellite scatterometer wind velocity measurements are a new source of data for studies of seasonal‐to‐interannual ocean‐atmosphere interactions in the Arabian Sea, where the largest and steadiest wind speeds occur in northern summer. Three satellite wind velocity data products (named CMOD4, FD, and IFR2), all created from radar backscatter measured by the first European Remote Sensing Satellite (ERS‐1), were compared to moored‐buoy wind measurements recorded in the central Arabian Sea during October 1994 to October 1995. Orthogonal regression analysis of 74 collocations indicated IFR2 winds were more representative of buoy winds compared to CMOD4 and FD. IFR2 winds during 1995 are described, including the time of monsoon onset and the path of the Somali Jet. Monthly mean vertical transport across the bottom of the Ekman layer of the Arabian Sea north of 8°N, meridional Ekman transport along 8.5°N, and Sverdrup transport along 8.5°N were computed with IFR2 data from May 1992 to May 1996. During the 1992–1995 June–September southwest monsoon, upwelling into the Ekman layer of the Arabian Sea occurred at a mean rate of 3.4 Sv (1 Sv = 106 m3 s−1), which was one‐third smaller than the volume transport exiting within the Ekman layer across the southern boundary of the Arabian Sea, and the southward Sverdrup transport was 15 Sv. During the 1992–1996 December–March northeast monsoon, nearly 5 Sv sank below the bottom of the Ekman layer, 4 Sv entered the Arabian Sea in the Ekman layer, and the Sverdrup transport was negligible. Year‐to‐year transport variations were small.