16 year climatology of cirrus clouds over a tropical station in southern India using ground and space-based lidar observations

Abstract

Abstract. 16 year (1998–2013) climatology of cirrus clouds and their macrophysical (base height, top height and geometrical thickness) and optical properties (cloud optical thickness) observed using a ground-based lidar over Gadanki (13.5° N, 79.2° E), India, is presented. The climatology obtained from the ground-based lidar is compared with the climatology obtained from seven and half years (June 2006–December 2013) of Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) observations. A very good agreement is found between the two climatologies in spite of their opposite viewing geometries and difference in sampling frequencies. Nearly 50–55% of cirrus clouds were found to possess geometrical thickness less than 2 km. Ground-based lidar is found to detect more number of sub-visible clouds than CALIOP which has implications for global warming studies as sub-visible cirrus clouds have significant positive radiative forcing. Cirrus clouds with mid-cloud temperatures between −50 to −70 °C have a mean geometrical thickness greater than 2 km in contrast to the earlier reported value of 1.7 km. Trend analyses reveal a statistically significant increase in the altitude of sub-visible cirrus clouds which is consistent with the recent climate model simulations. Also, the fraction of sub-visible cirrus cloud is found to be increasing during the last sixteen years (1998 to 2013) which has implications to the temperature and water vapour budget in the tropical tropopause layer.

Exploring the inorganic composition of the Asian Tropopause Aerosol Layer using medium-duration balloon flights

“…16-year climatological assessment of cirrus clouds, their microphysical, and optical properties were observed using a ground-based lidar over Gadanki, India (Pandit et al, 2015). When compared with those obtained by CALIOP, the observations showed the presence of cirrus clouds of geometrical thickness less than 2 km.…”

“…When compared with those obtained by CALIOP, the observations showed the presence of cirrus clouds of geometrical thickness less than 2 km. Moreover, the increasing fraction of sub-visible cirrus clouds between 1998-2003 probably modified on the temperature and the water vapor budget in the Tropical Tropopause Layer (Pandit et al, 2015). To study the impact of convection on our measurements, we calculate back-trajectories from ZF2 and ZF3 using the Langley Trajectory Model (LaTM) driven by GEOS-5 winds (Fairlie et al, 2014) and locate the intersection with anvils and deep convective clouds observed through Cloud Top Brightness Temperature from the HIMAWARI-8 satellite (Vernier et al, 2018).…”