Impact of lowland deforestation on South West Indian tropical wet forests: cloud cover and rainfall

Cloud forests require immersion in cloud for their survival. Not only are the locations of cloud forests in the Western Ghats of southwest India not well known, but also unknown are how they survive the peak dry season months of February to April.

MODIS imagery on the EOS-AM (Terra) and EOS-PM (Aqua) platforms shows that during the morning hours the potential cloud forest locations are relatively cloud free, becoming cloud covered during the afternoon hours. This is a strong indicator that the Western Ghats of southwest India are under a convective environment during the dry season. The conditions in these tropical montane cloud forests (TMCF) contrast sharply with those found at other sites, such as at Monteverde, Costa Rica.

The Colorado State University Regional Atmospheric Modeling System (CSU RAMS), driven with the National Center for Environmental Prediction (NCEP) reanalysis data sets, rawinsondes and surface station data are used to simulate the impact of deforestation in the region. In particular, two realistic land use scenarios (pristine forests, and current conditions) are simulated for two TMCF locations. Results suggest that the major source of moisture for these forests is not from cloud interception (horizontal precipitation) which is typical for other TMCFs, but from convective rainfall. Deforestation in these regions has intensified the convective regime, thereby increasing the afternoon cloud cover and rainfall. A third potential site currently is being investigated.