Signatures of Tibetan Plateau heating on Indian summer monsoon rainfall variability

Abstract

[1] Despite recent challenges, conventional wisdom has held that heating over the Tibetan Plateau leads to increased Indian summer monsoon rainfall via enhancement of cross-equatorial circulation aloft, and a concurrent strengthening of both the Somali Jet and westerly winds that bring moisture to southern India. We show that such heating, quantified by monthly estimates of moist static energy in the atmosphere just above the surface, correlates with summer monsoon rainfall, but only in the early (20 May to 15 June) and late (September 1 to 15 October) monsoon season. Correlations during the main monsoon season (15 June to 31 August) are small and insignificant. The positive correlations with early and late monsoon season, however, allow for heating over Tibet to modulate as much as 30% of the total rainfall. Furthermore, we demonstrate that heating over Tibet is independent of the El Niño Southern Oscillation, so that together they explain a substantial portion of variability in the early and late season rainfall, providing potential predictability. These links may also explain the wet conditions over India during early Holocene time and provide a quantitative link between a rise of Tibet and stronger Somali Jet.

Relative role of pre-monsoon conditions and intraseasonal oscillations in determining early-vs-late indian monsoon intensity in a GCM

“…It was shown by several previous studies that the MSE and vertical moist-static stability (VMS) of the atmosphere play pivotal role in determining the intensity of convection (Neelin and Held 1987;Zhang 1994;Nanjundiah 2000;Rajagopalan and Molnar 2013). The surface MSE just before the onset of monsoon is one of the precursory measures for the subsequent monsoon season (Chakraborty et al 2006).…”

Topology and seasonal evolution of the network of extreme precipitation over the Indian subcontinent and Sri Lanka

“…We infer that the Tibetan Plateau pattern influences not only the ISM, but also pre-monsoon and post-monsoon dynamics. Also, it has been argued in the literature that this region influences the ISM rainfall dynamics (Feng, 2005;Wang, 2006;Rajagopalan and Molnar, 2013).…”

The atmospheric branch of the hydrological cycle over the Indus, Ganges, and Brahmaputra river basins

“…During the boreal winter, the meltwater is extremely important in the Indus basin and is also important for the Brahmaputra basin, but plays only a modest role for the Ganges (Immerzeel et al, 2010). Indeed, the IRB irrigation system (IBIS) is the largest irrigation system in the world (Qureshi, 2011;Laghari et al, 2012). From a geographic and climatologic perspective, the IRB is at a transition between the monsoon system in the east and the Mediterranean system in the west (Karin and Veizer, 2002).…”

“…Solar heating is considered a fundamental driver of all of the monsoon systems. Heating of the Tibetan Plateau leads to increased ISM rainfall via enhancement of the cross-equatorial circulation and a concurrent strengthening of both the Somali jet and westerly winds that bring moisture to southern India (Rajagopalan and Molnar, 2013). Surface heating over the plateau plays a role in producing cy-clonic vorticity in the shallow lower layer but negative vorticity in the deep upper layers through atmospheric thermal adaptation (Yanai and Wu, 2006;Song et al, 2010).…”