Monday, 12 January 2009
Cloud climatology over the western ghats of southern india
Hall 5 (Phoenix Convention Center)
Cloud climatology over Southern India was generated using 7200 Aqua and Terra MODIS scenes with 1 km spatial resolution for the years 2002 to 2008. A neural network classified each scene into land, water, dust, smoke, cirrus clouds and various types of water clouds such as cumulus and stratus. Water clouds were extracted and aggregated on a monthly basis to create the water cloud climatology, with emphasis over the Western Ghats. CloudSat and CALIPSO measurements were used to examine spatial variations in liquid water content, cloud top height and cloud base height, especially over the mountains. Clouds are less common in the dry seasons and more common in the monsoon seasons; there is a diurnal pattern in both the dry and wet season with cloud cover increasing from the morning Terra overpass at 10:30 local time to 13:30 local time; and cloud cover is positively correlated with elevation. The results suggest that Western Ghats cloud forests exist because they are immersed in afternoon clouds during the dry season. CloudSat measures reflectivity in 125 vertical bins (each 500m resolution) providing detailed knowledge on the cloud interior properties (liquid water content (LWC), optical thicknes, and effective drop radius) leading to more accurate cloud base height estimates for mapping and monitoring the global cloud forests. Cloud LWC over the Ghats tends to show multiple peaks in the vertical distribution, demonstrating the prevalence of high and middle level clouds. The CPR and Lidar integrated measurements provide cloud base height and cloud top height. These measurements allow verification of cloud base height estimates derived independently from MODIS imagery, from which it is possible to map the cloud forests in this region of the world. In particular, we note that cloud immersion in Ghat cloud forests is maximum during the afternoon hours, as opposed to the morning hours in Central America.