ThecharacteristicsandpossiblephysicalmechanismofinterdecadalvariationoftheintensityoftheSouthAsianHigh(SAH)insummerareanalyzedusingtheNCEP/NCARreanalysisdataandNOAAextendedreconstructedseasurfacetemperature(SST)data.Theresultsindicatethataremarkableinterdecadaltransitionoccurredinthelate1970sthatincreasedtheintensityofSAH,or,anabruptclimatechangewasaround1978.AcomparativeanalysisbetweentheweakandstrongperiodoftheSAHintensityshowsthattherelatedanomalouspatternsoftheatmosphericcirculation(includingwindfield,airtemperaturefieldandverticalvelocityfield)arenearlyoppositetoeachother.Thesurfacelatentheatfluxanomaliesovertheplateau(especiallyinthenorthwestoftheplateau)insummerexertgreatinfluenceontheinterdecadalvariationoftheSAHintensityandthesurfacesensibleheatfluxanomaliesplayamoreimportantrole.ConsistentwiththeinterdecadalvariationoftheSAHintensity,themonopolemodeofthetropicalIndianOceanSSTinsummeralsoexperiencedalowtohightransitioninthelate1970s.Tosomeextent,thiscanrevealtheimpactoftheanomalousmonopolemodeofthetropicalIndianOceanSSTinsummeroninterdecadalvariationoftheSAH.
