RESEARCH ARTICLE


Simulation and Comparison Between Mid-Holocene and Preindustrial Indian Summer Monsoon Circulation Using a Regional Climate Model



Stefan Polanski*, 1, Annette Rinke2, Klaus Dethloff2, Stephan J. Lorenz3, Yongbo Wang2, Ulrike Herzschuh2, 4
1 Freie Universität Berlin, Institute for Meteorology, Carl-Heinrich-Becker-Weg 6-10, D-12165 Berlin, Germany
2 Alfred Wegener Institute for Polar and Marine Research, Research Unit Potsdam, Telegrafenberg A43, 14473 Potsdam, Germany
3 Max Planck Institute for Meteorology, Bundesstraße 53, D-20146 Hamburg, Germany
4 Potsdam University, Institute for Earth and Environmental Sciences, Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany


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© 2012 Polanskiet al;

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Freie Universitat Berlin, Institute for Meteorology, Carl-Heinrich-Becker-Weg 6-10, D-12165 Berlin, Germany; Tel: +49 30 838 71149; E-mail: stefan.polanski@met.fu-berlin.de


Abstract

The regional climate model HIRHAM has been applied over the Asian continent from 0°N to 50°N and 42°E to 110°E to simulate the Indian monsoon circulation under past and present-day conditions. The model is driven at the lateral and lower boundaries by the atmospheric output fields of the global coupled Earth system model ECHAM5- JSBACH/MPIOM for 44-years-long time slices during the mid-Holocene and the preindustrial present-day climate. Simulations with a horizontal resolution of 50 km are carried out to analyze the regional monsoon patterns under different external solar forcing and climatic conditions. The focus is on the investigation of the HIRHAM simulated summer monsoon circulation and the comparison of the regional atmospheric circulation and precipitation patterns between the paleo- and the preindustrial climate. Due to mid-Holocene changes in the atmospheric circulation with a reduced and southward shifted monsoonal flow across Arabian Sea and Bay of Bengal, an increase of summer rainfall at the windward slopes of western and southern Himalayas as well as over southern India and decreased rainfall over central India appear which is in agreement with proxy-derived precipitation reconstructions. During the mid-Holocene as well as for the present-day climate the same driving mechanisms for the summer monsoon in extreme wet monsoon years related to regional SST anomalies in the Indian Ocean and convective processes can be verified. Positive (negative) SST anomalies in the northern Indian Ocean enhance (inhibit) the local convection associated with a deepening (weakening) of the low pressure and trigger wet (dry) rainfall anomalies.

Keywords: Mid-Holocene, Present-Day, Indian Summer Monsoon, Regional Climate Model, Extreme Rainfall, Reconstructions.