Lidar investigations on the structure and microphysical properties of cirrus at a tropical station Gadanki (13.5° N and 79.2° E), India

Abstract

Cirrus clouds are mainly composed of ice crystals and are known to be the major natural contributors to radiative forcing in the Earth’s atmosphere system. Describing the formation and microphysical properties of cirrus clouds and their role in climate models remain a challenging study. Lidar is a unique instrument, which provides the information on the optical and microphysical properties of cirrus clouds with good spatial and temporal resolutions. In this study we present the microphysical properties of cirrus clouds and their temporal variability, obtained using the ground based dual polarisation lidar at the tropical station Gadanki (13.5° N and 79.2° E), India, during the period January2009 to March 2011. Using the method developed in house for deriving range dependent lidar ratio (LR), the lidar measurements are used for deriving the extinction coefficient and to obtain the nature of the scatterers present in the cloud. It is noted that lidar ratio plays an important role and its measurements indicate directly the type of the ice nucleating aerosol particles present in the cloud. The long term data obtained on the structure of the cirrus in this regard are useful in the climate modelling studies.