Micro Pulse Lidar measurements in coincidence with CALIPSO overpasses: Comparison of tropospheric aerosols over Kattankulathur (12.82oN, 80.04oE)

In this paper, we present validation of the cloud aerosol lidar with orthogonal polarization (CALIOP) level 1 and level 2 tropospheric aerosols products in coincidence to Micro Pulse Lidar (MPL) observations under different sky conditions and different seasons during March 2016–December 2018 over a tropical coastal station Kattankulathur (12.83oN, 80.04oE). In total, 33 simultaneous profiles during clear-sky (18 cases) and cloudy (15 cases; 7 mid-tropospheric (MT) clouds and 8 cirrus clouds cases) conditions are observed, out of which 5, 13, 6, and 9 cases are during winter, pre-monsoon, southwest (SW) monsoon and northeast (NE) monsoon seasons, respectively. CALIOP underestimates MPL within the boundary layer and overestimates in the free troposphere during both the clear-sky and cirrus conditions. In the clear-sky conditions, the mean bias of the level 1 aerosol products is found to be −14 ± 29% (18 ± 19%) below 3.0 km (over 3–10 km) while it is −39 ± 26% (33 ± 24%) below 3.0 km (over 3–8 km) underlying the cirrus clouds. The comparison underlying the thick MT clouds is not reliable. However, a better comparison is observed in the cases of thin MT clouds. A strong seasonal variation in the vertical distribution of the aerosol loadings near the surface with maximum (minimum) loading ~0.01 ± 0.005 km−1sr−1 (~0.004 ± 0.002 km−1sr−1) is observed during the winter (SW monsoon) season. The mean bias of level 2 aerosol profiles over the altitude 0.3–5 km is found to be 14 ± 28 % , 15 ± 44 % , −14 ± 25 % , and 24 ± 34% during the winter, pre-monsoon, SW monsoon, and NE monsoon seasons, respectively.