Lidar studies on microphysical influences on the structure and lifetime of tropical cirrus clouds

Abstract. An understanding of the role of ice crystals in the cirrus cloud is significant on the the radiative budget of the planet and consequent changes in the temperature. The structure and composition of the cirrus is affected by the microphysical parameters and size and fall speed of ice crystal inside the clouds. In this study, the structure and dynamics of tropical cirrus clouds were analysed by the microphysical characterisation using the data obtained by the ground based lidar system over the tropical site Gadanki [13.50° N, 79.20° E], India for a period of 6 years from 2005 to 2010. The observed clouds have optical depth within the range 0.02 to 1.8, lidar ratios are in the 20 to 32 sr range and depolarisation ratio varies between 0.05 and 0.45. The altitude and temperature dependence of the parameters, their interdependence and the fall velocity – effective size analysis were investigated. Dependence of the microphysical parameters on the ice fall velocity which is critical for climate change was also analysed. The same are compared with the CALIPSO satellite based CALIOP lidar observations.