ABSTRACT

Ahmedabad is an urban site in western region of India. Dust loading and its variability are very high over this semi-arid location. A state-of-the-art ground-based Raman lidar has been used for the study of day-to-day variability in vertical distribution of aerosol loading over Ahmedabad (23.02° N, 72.57° E) from 8 to 11 May 2018. We have done a comprehensive study about vertical profiles of aerosols across two wavelengths recorded simultaneously, namely, 355 nm and 532 nm, over this location. An interesting hump feature has been noted on 9 May at around 18 h (Local Time), with an additional peak at 19 h on 10 May. The loading over this region has more fine-mode aerosols than coarse-mode particles. Further, findings from ground-based lidar have been compared with MACC-II model simulations and Cloud-Aerosol Lidar with Orthogonal Polarization on-board Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observational. Back-trajectory analysis showed majority of the influx came from middle-east, carrying mineral dust and traces of marine aerosols from Arabian Sea, except for 11 May, where low-level dust carrying trajectories and also coarser dust particles were not seen. This type of manifestation has also been observed while classifying aerosols over Ahmedabad using Lidar Depolarization Ratio and Lidar Ratio obtained from Raman Lidar. Fine mode aerosols have been characterized as industrial, vehicular and marine, while coarser as mineral dust and biomass burning. This study focuses on local variation and classification of aerosols based on size and type, which will further help in better estimation of radiative budget and other impacts of aerosols.

摘要

艾哈迈达巴德是印度西部地区的一个城市遗址。在这个半干旱地区，灰尘负荷及其变化非常高。最先进的地面拉曼激光雷达已用于研究 2018 年 5 月 8 日至 11 日在艾哈迈达巴德（北纬 23.02°，东经 72.57°）上空气溶胶载荷垂直分布的日常变化。我们对同时记录的两个波长（即 355 nm 和 532 nm）上的气溶胶垂直剖面进行了全面研究。5 月 9 日大约 18 小时（当地时间）出现了一个有趣的驼峰特征，5 月 10 日的 19 小时还有一个额外的峰值。该区域的负载具有比粗模式粒子更多的细模式气溶胶。更远，地面激光雷达的发现已与 MACC-II 模型模拟和具有正交极化机载云气溶胶激光雷达和红外探路者卫星观测的云气溶胶激光雷达进行了比较。回溯轨迹分析显示，大部分涌入来自中东，携带矿物粉尘和来自阿拉伯海的海洋气溶胶痕迹，但 5 月 11 日除外，那里没有看到低层粉尘携带轨迹和较粗的粉尘颗粒。在使用从拉曼激光雷达获得的激光雷达去极化比和激光雷达比对艾哈迈达巴德上空的气溶胶进行分类时，也观察到了这种表现形式。细模式气溶胶被表征为工业、车辆和海洋，而粗模式气溶胶为矿物粉尘和生物质燃烧。