An Alternative Index for the Onset of the Summer Monsoon over the South China Sea

(整期优先)网络出版时间:2004-01-11
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AnalternativeindexfortheonsetofsummermonsoonovertheSouthChinaSea(SCS)hasbeendesignedbasedonthereanalysisdataoftheNationalCentersforEnvironmentalPrediction-NationalCenterforAtmosphericResearch(NCEP/NCAR).ItisfoundthatthedifferencebetweenthegeopotentialthicknessoverGuangzhouandManilacanbeusedasanalternativeindexfortheonsetofsummermonsoonovertheSCS.SincetheconvectiveheatingaltersthegeopotentialheightandthedistancebetweenGuangzhouandManilaisofsynopticscaleinthegeostraphicframework,theindexcanrepresentthestrengthofheatingandthefirstbarocliniccellovertheSCS.Bycomparisonbetweendifferentindices,itisfoundthatthesummermonsoononsetovertheSCScanbeascertainedbytheverticalzonalwindshearbetween200hPaand850hPa,thezonalwindat850hPa,theOLRanomaly,andthealternativeindexdefinedinthepresentpaper.Themeridionalwindshearbetween200hPaand850hPaalwaysappearsovertheSCSmuchearlierthanthezonalwindshearandcannotbeusedasanindexunderconsideration.