Alladi Ramakrishnan Hall

The Tibetan Plateau, Sun and, the Indian Monsoon Rainfall

Balaji Rajagopalan

University of Colarado

Despite recent challenges, conventional wisdom has held that heating over
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 (May 20 –
June 15) and late (September – October 15) monsoon season.  Correlations
during the main monsoon season (June 15 - 31 August) are small and
insignificant.  The positive correlations with early and late monsoon
reason, 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 El Niño Southern Oscillation (ENSO), 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.