Abstract
Weakening of Indian summer monsoon rainfall (ISMR) is traditionally linked with large-scale perturbations and circulations. However, the impacts of local changes in land use and land cover (LULC) on ISMR have yet to be explored. Here, we analyzed this topic using the regional Weather Research and Forecasting model with European Center for Medium range Weather Forecast (ECMWF) reanalysis data for the years 2000–2010 as a boundary condition and with LULC data from 1987 and 2005. The differences in LULC between 1987 and 2005 showed deforestation with conversion of forest land to crop land, though the magnitude of such conversion is uncertain because of the coarse resolution of satellite images and use of differential sources and methods for data extraction. We performed a sensitivity analysis to understand the impacts of large-scale deforestation in India on monsoon precipitation and found such impacts are similar to the observed changes in terms of spatial patterns and magnitude. We found that deforestation results in weakening of the ISMR because of the decrease in evapotranspiration and subsequent decrease in the recycled component of precipitation.
Highlights
Indian summer monsoon rainfall (ISMR) contributes 80% of the total annual precipitation in India[1,2] and controls the agricultural productivity and economy of the country
To understand the effects of such changes, we simulated the regional monsoon with weather research and forecasting (WRF) coupled with Community Land Model (CLM4.0), forced with different land use and land cover (LULC) types
We performed a sensitivity analysis to quantify the impacts of large-scale conversion from woody savannah to crop land in India on monsoon precipitation
Summary
Indian summer monsoon rainfall (ISMR) contributes 80% of the total annual precipitation in India[1,2] and controls the agricultural productivity and economy of the country. Roxy et al.[11] found that changes in ISMR may be attributed to a warming of Western Indian Ocean and a subsequent weakening of the temperature gradient in SST over the Indian Ocean All of these hypotheses are supported by different models, but none of the models considers the recent changes in LULC over India. Ozturk et al.[19] found that changes in ET may affect drought intensity These results agree with a model-based study by Devaraju et al.[20], in which modeling of deforestation across the global monsoon region showed an 18% decline in precipitation in India. As the LULC are obtained for these two time scales using different methods from different sources [details in Methods], the detected deforestation may have considerable uncertainty We present these regional runs as a representative experiment to understand the impacts of large-scale deforestation on monsoon rainfall. The differences in simulated precipitation between the LULCs of 1987 and 2005 provide an estimate of changes in precipitation due to large-scale deforestation in India
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