Impact of decreased wetlands on microclimate of Kolkata, India

Abstract

The Landsat images were used to assess landuse/landcover (LULC) changes in Kolkata Metropolitan Development Area (KMDA) from 1990 to 2011 and in East Kolkata Wetlands (EKWs) from 1972 to 2011using a geographic object-based analysis (GeOBIA) technique and post-classification comparison. Then, the Weather Research and Forecasting (WRF) model was applied to investigate impacts of LULC dynamics on micro-climate using three scenario analyses (real condition scenario; urbanization scenario; and irrigate cropland expansion scenario). Results suggested that built-up area increased almost twice in 2011 when comparing it to 1990. The increased area was mainly coursed by conversions of wetlands and croplands. More specifically, EKWs decreased by 17.9% between 1972 and 2011. Urbanization can greatly increase regional temperature and stimulate sensible heat fluxes but reduce latent heat fluxes and albedo. On the contrary, the expansion of irrigated croplands decreased the temperature and sensible heat fluxes but increased latent heat fluxes and albedo.