Lidar studies on climate sensitivity characteristics of tropical cirrus clouds

Abstract

The cirrus clouds play an important role in the Earth's radiation budget due to their high frequency of occurrence, non-spherical ice crystal formations, and variability in the scattering/absorption characteristics. Mostly, the tropical cirrus clouds are considered as greenhouse modulators. Thus the parameterization of tropical cirrus clouds in terms of the micro-physical properties and the corresponding radiative effects are highly important for the climate studies. For characterizing the radiative properties of cirrus clouds, which depend on the size, shape and number of the ice crystals, the knowledge of extinction coefficient (σ) and optical depth (τ) are necessary. The σ provides information needed for understanding the influence of the scatterers on the radiative budget whereas the τ gives an indication on the composition and thickness of the cloud. Extensive research on the tropical cirrus clouds has been carried out by using a ground based and satellite based lidar systems. In this work, the characteristics of tropical cirrus cloud derived by using the data from the ground based lidar system over the tropical site Gadanki [13.5 0 N, 79.2 0 E], India during 2010 are presented. Some of the results are compared with those obtained by us from satellite based CALIOP lidar observations of the CALIPSO mission. It is observed that there is a strong dependence of the some of the physical properties such as occurrence height, cloud temperature and the geometrical thickness on the microphysical parameters in terms of extinction coefficient and optical depth. The correlation of both the σ and τ with temperature is also observed.

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

“…Fernald's inversion method is used to derive the extinction coefficient for the ground based NARL lidar data in the region up to 20 km. The methods are the same as employed in Motty et al,(2016) . Cloud optical depth Atmos.…”

“…During the observation period a total number of 152 data files were collected from the NARL lidar system ( Motty et al,2016) and 116 data files (Caliop observations are available from 2006 June onwards) from the nocturnal observations obtained using CALIOP in the region selected around Gadanki. In this study the Calipso observations with cloud top altitude greater than 8 km and those with CAD score in the range of 80-100 were only considered.…”

“…Earlier extensive experimental studies analysed the importance of cirrus clouds in the radiation budget using various techniques employing lidars (Liou, 1986;1988;Ramanathan et al, 1989;Sassen et al, 1989;Wang et al, 1996;Hartmann et al, 2001;Stubenrauch et al, 2010;Motty et al, 2015Motty et al, , 2016. Heymsfield and McFarquahar (1996) found that cirrus clouds distributed in the tropics and play an important role in radiative effects.…”