Monday, August 6, 2007 - 2:20 PM

SYMP 2-4: Simulating changes in land-atmosphere interactions from agricultural expansion and irrigation in India: Potential impacts on the Indian Monsoon

Ellen Marie Douglas1, Dev Niyogi2, Adriana Beltrán-Przekurat3, and Roger A. Pielke Sr.3. (1) University of Massachussetts - Boston, (2) Purdue University, (3) University of Colorado

India has the largest irrigated agricultural area on the planet.  More than 90% of India’s water use goes to support irrigated agriculture.  The Indian monsoon belt is a home to a large part of the world’s population and agriculture is the major land-use activity in the region.  In Douglas et al.(2006), we found that vapor fluxes in India have increased by 7% (117 km3) in the wet season and a 55% increase (223 km3) in the dry season.  Two-thirds of this increase was attributed to irrigated agriculture.  In a follow-up study using the Regional Atmospheric Modeling System (RAMS) we show that agricultural intensification and irrigation can modify the surface moisture and energy distribution, which alters the boundary layer and regional convergence, mesoscale convection, and precipitation patterns over the Indian monsoon region. Four experiments were conducted to simulate a rain event from 16 to 20 July 2002 over the Indian region: (i) a control with Global Land Cover land use and observed Normalized Difference Vegetation Index, (ii) an irrigated crop scenario, (iii) a non-irrigated crop scenario, and (iv) a scenario for potential (natural) vegetation. Results indicate that the simulated surface energy and moisture flux over the Indian monsoon region are sensitive to the irrigation intensity and this effect is more pronounced than the impact of land use change from the potential vegetation to the agricultural landscape. Irrigation increased the regional moisture flux which in turn modified the convective available potential energy. This caused a reduction in the surface temperature and led to a modified regional circulation pattern and changes in mesoscale precipitation. These agricultural changes, including irrigation modify the mesoscale convection and rain patterns in the Indian monsoon region. These regional changes in land use need to be considered in multi-decadal climate variability and change assessments.

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