Impact Of The Indian Summer Monsoon On Water Vapor Transport At The Southern Boundary Of The Qinghai-Tibet Plateau And Cloud Precipitation In The Hinterland Of The Platea

Water vapor transport plays a significant role in maintaining the water cycle over the Tibetan Plateau(TP).This study investigates the characteristics of water vapor transport across TP southern boundaries and its impacts on TP hinterland precipitation during the Indian summer monsoon(ISM)season from 2000 to 2019.The southern boundary is subdivided into four sub-boundaries from the east to the west: boundaries 7(100°-95°E),8(95°-89°E),9(89°-80°E),and 10(80°-70°E)(B7,B8,B9,and B10).An area with concentrated spatial precipitation in both strong and weak ISM months is regarded as a precipitation concentration region(PCR)(30°-32.5°N,85°-90°E).The results show that:(1)The water vapor transport of the southern boundary of the Tibetan Plateau is mainly affected by the mid-latitude westerlies and the ISM.The former dominates the water vapor transport through B10,while the latter mainly transports water vapor to the plateau through B8,B9,and B10,which is the main source of water vapor in plateau summer.(2)Regardless of the strength of the ISM,the PCR precipitation is positively correlated with the water vapor transport through B10.The PCR precipitation shows a more dependable relationship to the water vapor transport from the BOB and the Arabian Sea via B8 and B9 in strong ISM months than in weak ISM months.B7 is a water vapor input boundary in both strong and weak ISM months.However,since PCR is located northwest of the B7,and the plateau is dominated by the enhanced westerly wind in ISM strong and weak months,it is difficult to transport the moist airflow through B7 to PCR and further affect its precipitation.(3)The PCR precipitation is larger in the strong ISM months than in the normal months for each hour of the day.The difference of PCR precipitation between strong and normal ISM months shows a significant increase from 11 LT to 17 LT.Water vapor from the Arabian Sea and the northern Bay of Bengal reached the PCR region respectively through B9 and B8.Both of the two factors provided water vapor for convective precipitation in the PCR region and shallow precipitation in the middle cloud,resulting in an increase in PCR precipitation during this period.(4)The PCR precipitation is smaller in the weak ISM month than in the normal month for most of the day except in the nighttime(20-22LT).The water vapor transport via B8 and B10 provided most of the water vapor for the convective development in the PCR region and the development of precipitation clouds in the middle cloud.The water vapor transport through B9 also contributed part of the water vapor,which led to the increase of precipitation during this period.