Comment on acp-2021-798

Abstract

Listen

Translate article

Knowledge of the spatiotemporal coverage of the cirrus clouds is vital in quantifying the radiation budget of the earth-atmosphere system. In this paper, we present the diurnal and vertical distributions of the occurrence of the cirrus clouds during different seasons as well as its interannual variation over Kattankulathur (12.82° N, 80.04° E), east coast of the Bay of Bengal. The long-term (2016–2018) continuous observations of micropulse lidar (MPL) demonstrate the laminar and descending cirrus clouds that occur either as single or multiple layers. The single-layer cirrus occurrence shows a diurnal pattern with frequent occurrence in the late evening (~30–40 %) while multiple-layer cirrus clouds occurrence and early morning (~10–20 %), respectively. For the diurnal pattern in single layer cirrus cloud occurrences, convective processes dominate during the pre-monsoon, southwest (SW), and northeast (NE) monsoon seasons, while the freeze-drying process is favourable during the winter season. However, both convective and freeze-drying processes are dominant in the diurnal pattern of the multiple-layer cirrus occurrences. The occurrence is maximum (~40 %) during the SW and NE monsoon seasons and minimum (~25 %) during the winter. The vertical distributions indicate that the maximum occurrence is confined within the tropical tropopause layer (TTL) during all the seasons. The cirrus cloud rarely occurs above the tropopause; however, it frequently occurs below the TTL during all the seasons. The vertical extent of the occurrence has broader altitude coverage (~8–17 km) during December–March and June–September while narrower during April–May (~10–17 km) and October–November (~9–15 km). The cirrus clouds occurrence also exhibits interannual variations with higher occurrence during 2016 compared to 2017 and 2018 in association with El Nino Southern Oscillation (ENSO).