Diurnal variation of rainfall in the Yangtze River Valley during the spring-summer transition from TRMM measurements

• Published in: Journal of Geophysical Research: Atmospheres Vol. 117; no. D6
• Main Authors: Chen, Guixing, Sha, Weiming, Iwasaki, Toshiki, Ueno, Kenichi
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 27-03-2012; American Geophysical Union
• Subjects: Atmospheric sciences; Climate change; diurnal variation; Diurnal variations; Dry season; Earth; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geophysics; monsoon; Precipitation; Rainfall; Rivers; Troposphere; Yangtze River valley; Asia; China; Europe; Qinghai-Xizang Plateau; Southern Europe; Italy; Marches Italy; Far East; China, People's Rep., Xizang, Tibetan Plateau; China, People's Rep., Changjiang R; Archive; Night; springs; Summer; cycles; air; slopes; troposphere; Variance; Convergence; convection; diurnal variations; winds; Spring(season); Rainy season; rainfall; atmospheric precipitation; eruptions; Regional scope; Satellite observation; Rainfall rate; phase shift; Dry season; growth; TRMM satellite
• ISSN: 0148-0227; 2169-897X; 2156-2202; 2169-8996
• DOI: 10.1029/2011JD017056

A 12 year archive of the Tropical Rainfall Measuring Mission (TRMM) rain rate is used to document the regionality of diurnal rainfall cycle in the Yangtze River Valley (YRV). The regional rain peaks, local phase shifts, rain event's behavior, and related seasonal change from March to August are examined. In the middle reach of YRV, rainfall appears mainly in early morning and displays a distinct local shift of diurnal phase. Such features are well established at each presummer (from May to June) and result from the eastward migrating events with a late night growth in size. They are supported by the low‐level convergence that moves from the east slope of the Tibetan Plateau to the middle reach of YRV, as the deviated wind vector rotates clockwise to enhance southerlies at late night and southwesterlies in the morning. In the lower reach of YRV, however, one observes an eruption of morning rainfall with less local difference in diurnal phase. Morning rainfall is active in presummers of some years but suppressed in some others, contributing greatly to the variance of rainfall budget and resulting in anomalous wet/dry seasons. It is found to arise from a local growth of rain events rather than the migrating events from the middle reach. A majority of these organized convections prefer to form and develop in a belt‐shaped zone where the nocturnal southwesterlies of warm/moist air impinge on the Meiyu front in the lower troposphere.
Key Points
Two modes of diurnal cycle explain the distinct regionality of rainfall
Space scale and movement of rain events play a role in diurnal cycle formation