The Response Of Precipitation Changes On The Qinghai-Tibet Plateau To Changes In The Indian Monsoon

Based on the 1973 to 2014 NCEP/NCAR reanalysis data,China national meteorological information center ground precipitation grid data and Indian institute of tropical meteorology precipitation data.Through relevance analysis,synthesis analysis,wavelet analysis and other analysis methods.According to interannual,seasonal and intraseasonal variations,discussed the influence of Indian summer monsoon on summer precipitation over the plateau and its large-scale circulation during the period.Further,the characteristics of low frequency oscillation of Indian summer monsoon and plateau summer precipitation and their influence on precipitation in China are also analyzed.The results show that :(1)The summer precipitation in the eastern and western parts of the plateau under theinfluence of Indian summer monsoon shows opposite variation characteristics.That is,the western plateau has more(less)precipitation and the eastern plateau has less(more)precipitation in Indian summer monsoon strong(weak)years.(2)From the synthetic analysis of the sea level pressure field,wind field and altitude fieldin Indian summer monsoon strong and weak years,it can be concluded that: when theIndian summer monsoon is strong(weak),the center of the Indian low-pressure isstronger(weak);The 850 hPa and 600 hPa anomalous wind fields show that the Indianregion is a strong cyclone(anticyclonic)circulation,corresponding to thestrengthening(weakening)of the Indian low pressure,the western plateau has more(less)precipitation and the eastern plateau has less(more)precipitation;The 100hPaanomalous height field shows that when the South Asia High and the easterly jetstrengthens(weakens),the western plateau has more(less)precipitation and theeastern plateau has less(more)precipitation;In northern India,there is a significantcyclonic(anticyclonic)water vapor transport.Correspondingly,at 600 hPa,the watervapor flux divergence shows a negative(positive)anomaly in the western plateau anda positive(negative)anomaly in the eastern plateau,resulting in more(less)precipitation in the western plateau and less(more)precipitation in the eastern plateau.(3)From monthly analysis in summer,when the Indian summer monsoon is strong(weak),The South Asian High in the upper troposphere is stronger and locatedwestward and northward(weaker and eastward and southward);In the middle andlower troposphere,the Indian Peninsula is an anomalous cyclone(anticyclone)circulation system.The western Tibetan Plateau is an anomalous convergence(divergence)flow field and the eastern part is an anomalous divergence flow field(convergence center or convergence zone);In the vertical velocity and 600 hPa watervapor flux divergence,the anomalous rise(sink)of the western plateau corresponds tothe convergence(divergence)of water vapor,while the anomaly sink(rise)in the eastcorresponds to the divergence(convergence)of water vapor in July and August;Correspondingly,the OLR is lower(higher)in the western plateau and the OLR ishigher(lower)in the eastern plateau.(4)The Indian summer monsoon,the Indian summer precipitation,the plateau summermonsoon and the plateau summer precipitation are all mainly oscillated in the periodof 30-70 days in 2006 and 2014.The trend of summer monsoon over the plateau ishighly correlated with summer precipitation over the eastern part of the plateau.Thatis to say,the index of summer monsoon over the plateau mainly reflects the change ofsummer precipitation over the eastern part of the plateau.During the active period ofthe strong Indian summer monsoon year,the convergence of the western part of theplateau strengthens,which is conducive to precipitation.During the interruptionperiod,the southerly wind in the eastern part of the plateau strengthens.During theactive period of the weak year of Indian summer monsoon,the air flow converges inthe western part of the plateau and diverges in the eastern part of the plateau.Duringthe interruption period,the northwest wind on the southwestern side of the plateau isnot conducive to the precipitation in the western part of the plateau,while the air flowconverges in the eastern part.