Abstract
While black carbon aerosols (BC) are believed to modulate the Indian monsoons, the radiative forcing estimate of BC suffers from large uncertainties globally. We analyze a suite of idealized experiments forced with a range of BC concentrations that span a large swath of the latest estimates of its global radiative forcing. Within those bounds of uncertainty, summer precipitation over the Indian region increases nearly linearly with the increase in BC burden. The linearity holds even as the BC concentration is increased to levels resembling those hypothesized in nuclear winter scenarios, despite large surface cooling over India and adjoining regions. The enhanced monsoonal circulation is associated with a linear increase in the large-scale meridional tropospheric temperature gradient. The precipitable water over the region also increases linearly with an increase in BC burden, due to increased moisture transport from the Arabian sea to the land areas. The wide range of Indian monsoon response elicited in these experiments emphasizes the need to reduce the uncertainty in BC estimates to accurately quantify their role in modulating the Indian monsoons. The increase in monsoonal circulation in response to large BC concentrations contrasts earlier findings that the Indian summer monsoon may break down following a nuclear war.
Original language | English |
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Pages (from-to) | 7833-7852 |
Number of pages | 20 |
Journal | Journal of Geophysical Research: Biogeosciences |
Volume | 121 |
Issue number | 13 |
DOIs | |
State | Published - 2016 |
Funding
This work was funded by a grant from the Office of Science (Biological and Environmental Research (BER)) of the U.S. Department of Energy (DOE) and used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract DE-AC05-00OR22725. The authors wish to thank the editor and two anonymous reviewers whose comments helped improve the manuscript. We thank Stefan Kinne of Max Planck Institute of Meteorology for providing us with AERONET BC AOD data. The model data presented in this study are available from the corresponding author upon request ([email protected]).