SST–convection relation over tropical oceans

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SST–convection relation over tropical oceans

Show simple item record Dr.Babu, C A Sabin, T P Joseph, P V 2014-05-17T07:51:24Z 2014-05-17T07:51:24Z 2012-04-28
dc.description Int. J. Climatol. (2012) en_US
dc.description.abstract According to current knowledge, convection over the tropical oceans increases with sea surface temperature (SST) from 26 to 29 °C, and at SSTs above 29 °C, it sharply decreases. Our research shows that it is only over the summer warm pool areas of Indian and west Pacific Oceans (monsoon areas) where the zone of maximum SST is away from the equator that this kind of SST-convection relationship exists. In these areas (1) convection is related to the SST gradient that generates low-level moisture convergence and upward vertical motion in the atmosphere. This has modelling support. Regions of SST maxima have low SST gradients and therefore feeble convection. (2) Convection initiated by SST gradient produces strong wind fields particularly cross-equatorial low-level jetstreams (LLJs) on the equator-ward side of the warm pool and both the convection and LLJ grow through a positive feedback process. Thus, large values of convection are associated with the cyclonic vorticity of the LLJ in the atmospheric boundary layer. In the inter-tropical convergence zone (ITCZ) over the east Pacific Ocean and the south Pacific convergence zone (SPCZ) over the west Pacific Ocean, low-level winds from north and south hemisphere converge in the zone of maximum SST, which lies close to the equator producing there elongated bands of deep convection, where we find that convection increases with SST for the full range of SSTs unlike in the warm pool regions. The low-level wind divergence computed using QuikSCAT winds has large and significant linear correlation with convection in both the warm pool and ITCZ/SPCZ areas. But the linear correlation between SST and convection is large only for the ITCZ/SPCZ. These findings have important implications for the modelling of largescale atmospheric circulations and the associated convective rainfall over the tropical oceans en_US
dc.description.sponsorship CUSAT AND CSIR en_US
dc.language.iso en en_US
dc.publisher Wiley Online Library ( en_US
dc.subject sea surface temperature and its gradient en_US
dc.subject atmospheric deep convection en_US
dc.subject warm pool en_US
dc.subject ITCZ and SPCZ en_US
dc.subject low-level jetstreams en_US
dc.title SST–convection relation over tropical oceans en_US
dc.type Article en_US

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