Wintertime wind forcing and sea surface cooling near the South India tip observed using NSCAT and AVHRR

Alvarinho J. Luis, Hiroshi Kawamura

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36 Citations (Scopus)


This report addresses a case of topographic air-sea interaction in the Gulf of Mannar, near the Indian tip, for the winter monsoon of 1996-1997. Using high spatial resolution NASA-Scatterometer (NSCAT) wind data, a 1°x1°region of strong wind is identified in the Gulf during the peak of the winter monsoon. The characteristic topography of South India and Sri Lanka and their orientation to the monsoon wind tend to channel this strong wind. Air-sea heat flux analyses, using the NSCAT wind and the European Center for Medium-Range Weather Forecast objective analyses surface data, reveal that the strong winter monsoon bursts cause large latent heat loss (180 W/m2) from a wind-fetch region centered on 7.5°N, 77.5°E during January. Weak air-sea temperature gradients result in weak sensible heat loss (<15 W/m2) from the ocean. The ocean response to this forcing is examined using weekly and monthly mean satellite-derived sea surface temperature (SST) maps; these indicate a sea surface cooling of about 1°C along the axis of the wind flow. A by-product of this cooling is an emergence of a SST front along the periphery of the strong wind-stress region. Time-series analyses of the surface meteorology reveal that this forcing has a periodicity of about 15 days, with a peak during the last week of December. Wind stress curl derived from, the NSCAT wind data exhibits high negative values (anticyclonic Ekman pumping) on a 2-week time scale, concomitant with strong wind bursts. The features observed in the Gulf of Mannar are similar to those reported from some other locations. (C) Elsevier Science Inc., 2000.

Original languageEnglish
Pages (from-to)55-64
Number of pages10
JournalRemote Sensing of Environment
Issue number1
Publication statusPublished - 2000 Jul
Externally publishedYes

ASJC Scopus subject areas

  • Soil Science
  • Geology
  • Computers in Earth Sciences


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