Intraseasonal Variation of Sea Surface Temperature over the Tropical Eastern Indian Ocean During Boreal Spring and Summer and Accompanied Atmospheric Response
ZHANG Meiyi
LI Xiuzhen
Abstract：The sea surface temperature(SST)over the tropical eastern Indian Ocean(TEIO)during boreal spring and summer shows a significant intraseasonal oscillation(ISO).Based on the NOAA OISSTv2.1 dataset,NOAA Interpolated Outgoing Longwave Radiation dataset and NCEP-DOE Reanalysis II data from 1982 to 2020,the characteristics of its intraseasonal variation and the associated atmospheric response were investigated by using power spectrum analysis,phase compositing and K-means clustering.The results show that the temporal variation of the SST anomalies over the TEIO was dominated by a period of 20-50-day,and the strong intraseasonal SST oscillation mainly occurred from April to July.A pronounced ocean-atmosphere interaction could be found over the TEIO at the intraseasonal timescale,with the SST warming leading local convection enhancement by 3/8 cycle and lagging convection suppression by 1/8 cycle.The convection anomalies driven by the intraseasonal SST showed a meridional dipole structure.It was characterized by a prominent northward propagation,with the intensity decaying rapidly during the northward movement and the convection in the north weaker than that in the south.Two significant kinds of atmospheric responses were extracted by using K-means clustering:the northward-moving response and the local response.The northward moving response occurred mainly in summer(June-July),showing a well-organized convective dipole structure with comparable intensity and clear northward propagation.During its northward movement,it affected the strength of the southwesterly monsoon over the Arabian Sea and the intraseasonal variation of the Indian Peninsula summer monsoon significantly.While the local response occurred mainly in the transition season between spring and summer(April-June),and the sole convection center developed and disappeared over the TEIO with a weak migration.Different types of atmospheric response to the intraseasonal SST variation can be attributed to different easterly shear over the North Indian Ocean.In summer,the easterly shear was strong,and the convection propagated northward following the vertical shear mechanism.However,the background easterly shear was weak in the transition season between spring-summer and the vertical wind shear mechanism was inapplicable.The weak vorticity advection mechanism caused the convection to move northward slightly,but it mainly developed and dissipated locally.
Keywords：tropical eastern Indian OceanSSTintraseasonal oscillationatmospheric responseK-means clustering
Publication Date：2024-06-28
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：13( 491-503 )