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11759Fwd: [karmayog] Re: monsoon moments

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  • Thiagarajan Arunachalam
    Jun 26, 2014
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      ---------- Forwarded message ----------
      From: 'karmayog - tanya' info@... [karmayog] <karmayog@yahoogroups.com>
      Date: Thursday, June 26, 2014
      Subject: [karmayog] Re: monsoon moments
      To: karmayog@yahoogroups.com


       

       
      39 pages
       
      The delayed effect of major El Niño events on Indian monsoon rainfall
       
      Abstract
      Major winter El Niño events produce warmer sea surface temperatures (SSTs) and
      intensify deep convection overthe south equatorial Indian Ocean during the subsequent
      early boreal spring. The above normal column-integrated water vapor associated with
      these conditions progresses northward into the North Indian Ocean (NIO) by the start of
      the South Asian summer monsoon season. The progression occurs as the weakening of
      monsoonal winds warms the NIO via reduced surface evaporation during the early
      monsoon season (Jun-Jul).

      Idealized atmospheric general circulation model (AGCM) experiments demonstrate the
      role of mixed layer thermal inertia of the tropical Indian Ocean in maintaining memory of
      the winter El Niño conditions through boreal spring. However, the remnant
      contemporaneous warm SSTs in the eastern equatorial Pacific following the winter El
      Niño can greatly enhance the NIO warming by weakening the monsoonal winds, and
      thereby extend the winter El Niño’s impact on the Indian Ocean by the summer monsoon
      season.

      The NIO warming generally increases moisture advection into the Indian subcontinent,
      but the reduced dry static energy advection associated with weaker monsoon circulation
      strength suppresses the precipitation increase during the early monsoon season (Jun-Jul).
      Monsoon convection strengthens as the warmer NIO increases surface latent heat flux
      and the monsoonal low-level winds start to rebound during the late monsoon season
      (Aug-Sep).


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