Effects of land use/land cover alterations on regional meteorology over Northwest India.

Irrigation activities, as part of the agricultural green revolution, in Northwest India are aimed at transforming barrenland to agriculturally productive area. The main objective of this study is to determine the effects of these land use land cover (LULC) transformations on regional meteorology over this region. Satellite derived LULC classes in 2003 and 2012 reveal conversion of significantly large areas of barrenland to open shrubland and open shrubland to cropland over Northwest India. Model simulations show that these LULC changes (LULCC) alone decreases sensible heat flux (SHF) over this region by -5.85 ± 0.24Wm and enhances latent heat flux (LHF) by 11.03 ± 0.41Wm, with prominent changes over the exact regions of LULCC. These alterations lead to decrease in surface level air temperature by -0.14 ± 0.005 K and increase in relative humidity by 1.48 ± 0.03%. While reanalysis data show increase (decrease) in LHF (SHF) at a rate of 8.5Wmdec (-5.67Wmdec), satellite measurements show increasing trend in near surface relative humidity at a rate of 2.13%dec with an increasing trend in daily mean air temperature (0.3Kdec). However, day time air temperature and diurnal temperature range decreases at rates of -0.007Kdec and - 0.6Kdec respectively. To delineate the contribution of LULCC from the measured trend of daily mean temperatures, Observation Minus Reanalysis (OMR) method has been employed. OMR analysis shows a decreasing trend in daily mean temperature (-0.48Kdec) and increasing trend in RH (6.85% dec), corroborating the model simulated changes. The study shows increase in vegetated area over Northwest India, which leads to increase in evapo-transpiration. This affects the regional meteorology by enhancing humidity and SHF and reducing LHF and temperature. These results demonstrate that the land-based mitigation strategies yield measurable climatic benefits over the period of one or two decades, in contrast to the much longer time period generally required for greenhouse gases to cycle through the climate system.