Land use change impacts on cloud and precipitation formation in the coastal regions of Sarawak, Malaysia

Over the last decade, peat swamp forests along the coastal regions of Sarawak, Malaysia have been cleared for agricultural purposes. The Center for Remote Imaging, Sensing and Processing (CRISP) Moderate Resolution Imaging Spectroradiometer (MODIS) derived land cover classification data show that changes in land use are dominated by conversion of peat swamp forests to oil palm plantation, open lowland and lowland mosaic categories. MODIS derived land products show sharp decrease in Normalized Difference Vegetation Index (NDVI) following the clearing of forests and subsequent increase as the oil palms mature. Surface albedo shows the opposite trend, where there is an increase following clearing and then decrease. Canopy height of the peat swamp forest is higher than the vegetation replacing the cleared areas and thus has smaller aerodynamic roughness. Land cover changes are also accompanied by increase in skin surface temperature indicating changes in Bowen ratio. Nested grid simulations using the Regional Atmospheric Modeling System (RAMS) over the central region of the Sarawak coast is used to investigate the impact of land use change on regional climate. Numerical simulations were conducted for August of 2009 for satellite derived land cover scenarios for years 2000 and 2010. Numerical simulations that incorporate these changes show substantial changes in pattern of simulated precipitation (~15-20% increase), potentially caused by changes in sea breeze circulation patterns. Land use and land cover changes, similar to that in Sarawak, has also occurred over other regions in Southeast Asia including Indonesia and could be impacting cloud and precipitation formation in these regions.