| In this study the potential future changes in different aspects of the Indian summer monsoon
(ISM) associated with the RCP-scenarios are assessed. Different kinds of mechanisms
leading to these changes will be addressed, with some of them working locally and some of
them remotely. The study is based on several sets of ensemble simulations with the newly
developed MPI-ESM. In one set of simulations (1850-2005), emissions and concentrations,
respectively, of the well-mixed greenhouse gases and the sulphate aerosol load have been
prescribed according to observations, in three other sets of simulations (2006-2100), the
aforementioned anthropogenic forcing agents have been prescribed according to the
RCP2.6-, RCP4.5- and RCP8.5-scenario, respectively. For each of these scenarios, one
simulation has been extended over the period 2101-2300, in accordance with the
CMIP5-protocol.
The three kinds of scenario simulations are characterized by marked changes in
different aspects of the ISM, such as an intensification of the summer monsoon
precipitation despite a weakening of the large-scale monsoon circulation. The magnitude of
these changes varies with the strength of the underlying scenario, with the strongest
(weakest) scenario showing the largest (smallest) changes, respectively. As for the
simulations extending to 2300, the RCP8.5-scenario shows a further amplification of the
projected changes in the ISM after 2100, finally reaching a state, where the monsoon
flow is broken down during June, shortening the monsoon season by about one
month. Despite the absence of the characteristic monsoon flow, the rainfall in the
Indian region is also increased during June. Considering the simulated changes
for the shortened monsoon season and for June separately, allows for a detailed
analysis of the different mechanisms leading to the projected increase in the monsoon
rainfall on one hand and the reduction of the large-scale monsoon flow on the other. |