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南亚城市上空气溶胶的垂直分层。

Vertical stratification of aerosols over South Asian cities.

机构信息

Institute of Environment and Sustainable Development, Banaras Hindu University, Varanasi, India; DST-Mahamana Centre of Excellence in Climate Change Research, Banaras Hindu University, Varanasi, India.

Institute of Environment and Sustainable Development, Banaras Hindu University, Varanasi, India.

出版信息

Environ Pollut. 2022 Sep 15;309:119776. doi: 10.1016/j.envpol.2022.119776. Epub 2022 Jul 13.

Abstract

This study examines vertically resolved aerosol optical properties retrieved from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard CALIPSO satellite over several cities across South Asia from March 2010 to February 2021. Atmospheric layer-specific stratification of aerosols and dominant aerosol sub-types was recognized over each city with their seasonal trends. A contrasting pattern in aerosol vertical distribution over cities across Indo-Gangetic Plain (IGP) was noted compared to non-IGP cities, with considerable dependency on geographic location of the city itself. In all the cases, total extinction decreased with increasing altitude however, with varying degree of slope. A clear intrusion of transported aerosols at higher altitude (>3 km) was also evident. Extinction coefficient of type-separated aerosols indicate robust contribution of smoke aerosols, urban aerosols/polluted dust, and mineral dust below 3 km height. At higher altitude (>3 km), dust and urban aerosols dominate over majority of the stations. Overall, 51% of total columnar aerosols remained within 0-1 km height over South Asian cities, slightly high over the IGP (57%) against non-IGP cities (39%). Such distribution also has a seasonal pattern with higher fraction of aerosols remaining below 1 km during post-monsoon (October-November, 62%) and winter (December-February, 72%) compared to summer months (March-May, 39%). When partitioned against planetary boundary layer (PBL), 41% (59%) of aerosols remained within the PBL (free troposphere) that too exhibiting strong diurnal variations irrespective of seasons. Dominating aerosol types and their contribution to total aerosol loading was explored by comparing type-based aerosol extinction against total aerosol extinction. Dust, smoke and urban aerosols emerged as three predominating aerosol types, while presence of marine aerosol was noted over the coastal cities. Major fraction of smoke and urban aerosols remained within 2 km height from surface. In contrast, efficient transport of dust aerosol above 2 km height was evident particularly over IGP during summer.

摘要

本研究利用搭载在 CALIPSO 卫星上的云-气溶胶激光雷达与正交偏振(CALIOP)仪器,从 2010 年 3 月至 2021 年 2 月期间,对南亚多个城市的垂直分辨气溶胶光学特性进行了研究。根据季节性变化,识别出了每个城市大气气溶胶的分层结构和主要气溶胶亚型。与非印度-恒河平原(IGP)城市相比,IGP 城市的气溶胶垂直分布呈现出截然不同的模式,这与城市本身的地理位置有很大关系。在所有情况下,总消光系数随高度的增加而减小,但斜率有所不同。在较高海拔(>3km)也明显存在输送气溶胶的入侵。经类型分离后的气溶胶消光系数表明,在 3km 以下高度,烟尘气溶胶、城市气溶胶/污染尘和矿物尘对气溶胶有显著贡献。在较高海拔(>3km),尘埃和城市气溶胶在大多数站点占主导地位。总的来说,南亚城市的总柱状气溶胶有 51%分布在 0-1km 高度范围内,IGP 地区(57%)略高于非 IGP 地区(39%)。这种分布也具有季节性模式,在季风后(10 月至 11 月)和冬季(12 月至 2 月)期间,低于 1km 的气溶胶比例(62%和 72%)高于夏季(3 月至 5 月)(39%)。根据与行星边界层(PBL)的划分,41%(59%)的气溶胶在 PBL(自由对流层)内,无论季节如何,这部分气溶胶都表现出强烈的日变化。通过比较基于类型的气溶胶消光与总气溶胶消光,探索了主要气溶胶类型及其对总气溶胶负荷的贡献。尘埃、烟雾和城市气溶胶是三种主要的气溶胶类型,而沿海城市则存在海洋气溶胶。在地表以上 2km 高度范围内,烟雾和城市气溶胶的主要部分仍然存在。相比之下,在夏季,IGP 地区上空的尘埃气溶胶能够有效地向上传输至 2km 以上高度。

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