Propagating convective system as a rainfall connection between southwestern Tibetan Plateau and Indian continent

Friday, 19 December 2014
Wenhao Dong, Yanluan Lin and Yuanyu Xie, Center for Earth System Science, Tsinghua University, Beijing, China
The Tibetan Plateau (TP) is called "Asia's Water Tower" because it is the headwaters of many major rivers in Asia, upon which the production and living of nearly 1/6 world population strongly depends. Precipitation and its future change over the TP pose a large socio-economic impact on the surrounding nations. Using multiple precipitation datasets and CMIP5 model simulations, summer (June to September) precipitation over the TP and Indian continent is investigated. We note a close linkage of rainfall over the southwestern Tibetan Plateau (SWTP) and central-eastern India. Such a linkage is maintained by frequent propagation of convective systems from northern Indian lower lands over the high mountain range into SWTP. An objective propagation identification method suggests such propagation contributes nearly half of the total summer rainfall in SWTP. The propagation is prominent from late June to mid-September. Its occurrence is rather stable and appears not to be strongly modulated by Indian monsoon strength. The propagation also modifies the rainfall diurnal cycle with a second peak near midnight in addition to the late afternoon peak induced by localized convective systems. Favorable environmental conditions for propagations are also explored.