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Warm pool thermodynamics from the Arabian Sea Monsoon Experiment (ARMEX)

DRS at CSIR-National Institute of Oceanography

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Title Warm pool thermodynamics from the Arabian Sea Monsoon Experiment (ARMEX)
 
Creator Sengupta, D.
Parampil, S.R.
Bhat, G.S.
Murty, V.S.N.
RameshBabu, V.
Sudhakar, T.
Premkumar, K.
Pradhan, Y.
 
Subject thermodynamics
monsoons
surface temperature
mixed layer depth
solar radiation
 
Description Before the onset of the south Asian summer monsoon, sea surface temperature (SST) of the north Indian Ocean warms to 30-32 degrees C. Climatological mean mixed layer depth in spring (March-May) is 10-20 m, and net surface heat flux (Q sub(net)) is 80-100 W m sup(-2) into the ocean. Previous work suggests that observed spring SST warming is small mainly because of (1) penetrative flux of solar radiation through the base of the mixed layer (Q sub(pen)) and (2) advective cooling by upper ocean currents. The role of these two processes in SST evolution from a two-week Arabian Sea Monsoon Experiment process experiment in April-May 2005 in the southeastern Arabian Sea is estimated. The upper ocean is stratified by salinity and temperature, and mixed layer depth is shallow (6 to 12 m). Current speed at 2 m depth is high even under light winds. Currents within the mixed layer are quite distinct from those at 25 m. On subseasonal scales, SST warming is followed by rapid cooling, although the ocean gains heat at the surface: Q sub(net) is about 105 W m sup(-2) in the warming phase and 25 W m sup(-2) in the cooling phase; penetrative loss Q sub(pen) is 80 W m sup(-2) and 70 W m sup(-2). In the warming phase, SST rises mainly because of heat absorbed within the mixed layer, i.e., Q sub(net) minus Q sub(pen); Q sub(pen) reduces the rate of SST warming by a factor of 3. In the second phase, SST cools rapidly because (1) Q sub(pen) is larger than Q sub(net) and (2) advective cooling is approx. 85 W m sup(-2). A calculation using time-averaged heat fluxes and mixed layer depth suggests that diurnal variability of fluxes and upper ocean stratification tends to warm SST on subseasonal timescale. Buoy and satellite data suggest that a typical premonsoon intraseasonal cooling event occurs under clear skies when the ocean is gaining heat through the surface. In this respect, premonsoon SST cooling in the north Indian Ocean is different from that due to the Madden-Julian oscillation or monsoon intraseasonal oscillation.
 
Date 2008-11-19T07:22:51Z
2008-11-19T07:22:51Z
2008
 
Type Journal Article
 
Identifier Journal Of Geophysical Research (C: Oceans), vol.113; doi:10.1029/2007JC004623, 17 pp
http://drs.nio.org/drs/handle/2264/1478
 
Language en
 
Rights Copyright [2008]. All efforts have been made to respect the copyright to the best of our knowledge. Inadvertent omissions, if brought to our notice, stand for correction and withdrawal of document from this repository.
 
Publisher American Geophysical Union