Optical properties of cirrus clouds in the tropical tropopause region during two contrasting seasons

155-166<span style="font-size:11.0pt;font-family: " times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:="" hi"="" lang="EN-GB">Radiation budget of Earth’s atmospheric system is largely impacted by the presence of cirrus clouds. In order to quantify the effect of cirrus clouds, particularly in tropics, it is important to characterise its vertical structure and optical properties. The variation of the optical and microphysical properties along with the structure and dynamics of the cirrus during two contrasting seasons, the summer and the southwest monsoon over the period 2006 - 2010 were studied using the ground-based lidar measurements made at the tropical station, Gadanki (13.5°N, 79.2°E), India. The related meteorological indicators derived from radiosonde data available with Wyoming Atmospheric Data Centre were analysed .The results were compared with the data obtained from the CALIOP on board the CALIPSO satellite. Both the observations show similar pattern of seasonal variation. In most of the cirrus clouds, the top height observed was 0.8 km above and below the tropopause and top height was maximum during monsoon season. The seasonal variation of optical depth showed that most of cirrus clouds were thin and the optical depth showed highest value during monsoon period.