Atmospheric Observations and Modelling Laboratory (AOML), Dept. of Physics, SRM Institute of Science and Technology, Kattankulathur 603203, India.
Atmospheric Observations and Modelling Laboratory (AOML), Dept. of Physics, SRM Institute of Science and Technology, Kattankulathur 603203, India; Indian Institute of Tropical Meteorology, Pune, India.
Sci Total Environ. 2023 Aug 15;886:163917. doi: 10.1016/j.scitotenv.2023.163917. Epub 2023 May 8.
The elevated aerosol layer (EAL) plays a vital role in weather and climate by modifying the Earth's radiation budget. In the present study, the EAL occurrence and its characteristics in the pre-monsoon season using micropulse lidar (MPL) observations during 2016-2018 and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) during 2007-2018 over Kattankulathur is being reported. We have collected 147 days (101 cases) of MPL (CALIPSO) observations during clear sky conditions in the pre-monsoon 2016-2018 (2007-2018), out of which EAL is observed for 56 days (61 cases). The EAL width is generally found to be 2.0 km and occurs between ~1.0 km and 5.0 km. Three different types of EALs are categorized based on their altitudinal occurrence using the zero-crossing method. The EALs with their base at ~1.0-1.5 km, ~1.5-2.0 km, and ~ 2.0-3.0 km are taken as types I, II, and III, which occur for 9, 20, and 27 days, respectively. The EAL significantly modifies the total columnar aerosol optical depth (AOD). It is found that AOD, in total, within ABL and EAL, are ~0.72 (0.61), 0.28 (0.25), and 0.45 (0.36) using MPL (CALIPSO), respectively. The aerosols within ABL contribute ~38 % (41 %) while EAL ~ 62 % (59 %) to the total AOD obtained using MPL (CALIPSO). We observed that the ABL and EAL are characterized by different aerosol subtypes, such as dust marine (31 %) and smoke ( 27 %) aerosols. Other aerosol subtypes, such as dust and polluted dust, commonly occur within the ABL (54 %) and EAL (52 %).
高层气溶胶层 (EAL) 通过改变地球的辐射预算，在天气和气候中起着至关重要的作用。本研究使用微脉冲激光雷达 (MPL) 在 2016-2018 年期间和云气溶胶激光雷达和红外探路者卫星观测 (CALIPSO) 在 2007-2018 年期间对金奈附近的前季风季节的 EAL 发生情况及其特征进行了报道。我们收集了 2016-2018 年前季风期间晴朗天气条件下的 147 天 (101 例) 的 MPL (CALIPSO) 观测数据，其中有 56 天 (61 例) 观测到了 EAL。EAL 的宽度通常在2.0km 左右，发生在1.0km 和 5.0km 之间。使用零交叉法根据其海拔高度对三种不同类型的 EAL 进行了分类。EAL 的基底在1.0-1.5km、1.5-2.0km 和2.0-3.0km 的 EAL 分别为 I 型、II 型和 III 型，它们分别出现了 9、20 和 27 天。EAL 显著改变了总柱气溶胶光学厚度 (AOD)。结果表明，使用 MPL (CALIPSO)，ABL 和 EAL 内的总柱 AOD 分别约为 0.72 (0.61)、0.28 (0.25) 和 0.45 (0.36)。ABL 内的气溶胶贡献了约 38% (41%)，EAL 贡献了62% (59%)，得到了 MPL (CALIPSO) 获得的总 AOD。我们观察到，ABL 和 EAL 的特征是不同的气溶胶亚型，如灰尘海洋 (31%) 和烟雾 (~27%) 气溶胶。其他气溶胶亚型，如灰尘和污染灰尘，通常存在于 ABL (54%) 和 EAL (52%)。
