Modeling dust sources, transport, and radiative effects at different altitudes over the Tibetan Plateau
Modeling dust sources, transport, and radiative effects at different altitudes over the Tibetan Plateau
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模拟青藏高原不同高度的沙尘源、输送和辐射效应
DOI：
10.5194/acp-20-1507-2020
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发表时间：
2020-02-07
影响因子：
6.3
通讯作者：
Yang, Ben
中科院分区：
文献类型：
--
作者：
Hu, Zhiyuan;Huang, Jianping;Yang, Ben
同时，青藏高原作为世界上地势最高的地区，能够影响沙尘羽流的洲际输送，形成不同高度沙尘的典型分布特征。本文采用全耦合气象化学模式WRF-Chem （Weather Research and Forecasting model with chemistry）和示踪标记技术，对青藏高原不同海拔高度的尘源贡献和输运特征进行了准全球模拟。总的来说，模拟较好地捕捉了卫星反演的不同高度的气溶胶光学深度（AOD）空间分布。模式结果表明，沙尘颗粒通过主要沙漠地区上空的上升气流排放到大气中，然后输送到高原。东亚沙尘（主要来自戈壁和塔克拉玛干沙漠）向南移动，上升到青藏高原，在青藏高原北坡3 km高度和12 km高度分别贡献了50 mg m（-2）和5 mg m（-2）的质量负荷。来自北非和中东的沙尘集中在6公里以下的南北斜坡上，其中3公里以下和9公里以上的质量载荷分别为10至100毫克和1至10毫克（-2）。当沙尘向北和TP上空输送时，在6 km高度以上的质量负荷为5-10 mg m（-2）。东亚向青藏高原输送的尘量通量为7.9 Tg yr(-1)，主要发生在3 ~ 6 km高度。来自北非和中东的沙尘颗粒跟随西风急流向东输送，然后进入西侧TP，沙尘质量通量分别为7.8和26.6 Tg yr（-1）。北非沙尘最大质量通量主要出现在0 ~ 3 km (3.9 Tg yr(-1))，中东沙尘最大质量通量出现在69 km （12.3 Tg yr(-1)）。尘流主要分布在TP的东侧（-17.89 Tg yr(-1)）和南侧（11.22 Tg yr(-1)），在6-9 km处出现峰值（8.7 Tg yr(-1)）。粉尘（按质量）集中在1.25 ~ 5.0 μ m的粒径范围内，粉尘（按颗粒数）集中在0.156 ~ 1.25 μ m的粒径范围内，与其他气溶胶相比，粉尘对总总总AOD的贡献超过50%。尘埃引起的直接辐射强迫在大气顶部（降温）为-1.28 W m(-2)，在大气中（升温）为0.41 W m(-2)，在地面（降温）为-1.68 W m（-2）。通过对不同源区的沙尘贡献及其相关辐射强迫的定量分析，可以更好地理解沙尘对青藏高原及周边地区气候的影响。
Mineral dust plays an important role in the climate of the Tibetan Plateau (TP) by modifying the radiation budget, cloud macro- and microphysics, precipitation, and snow albedo. Meanwhile, the TP, with the highest topography in the world, can affect intercontinental transport of dust plumes and induce typical distribution characteristics of dust at different altitudes. In this study, we conduct a quasi-global simulation to investigate the characteristics of dust source contribution and transport over the TP at different altitudes by using a fully coupled meteorology-chemistry model, the Weather Research and Forecasting model with chemistry (WRF-Chem), with a tracer-tagging technique. Generally, the simulation reasonably captures the spatial distribution of satellite-retrieved dust aerosol optical depth (AOD) at different altitudes. Model results show that dust particles are emitted into atmosphere through updrafts over major desert regions and then transported to the TP. The East Asian dust (mainly from the Gobi and Taklamakan deserts) is transported southward and is lifted up to the TP, contributing a mass loading of 50 mg m(-2) at a height of 3 km and 5 mg m(-2) at a height of 12 km over the northern slope of the TP. Dust from North Africa and the Middle East are concentrated over both of the northern and southern slopes below 6 km, where mass loadings range from 10 to 100 and 1 to 10 mg m(-2) below 3 km and above 9 km, respectively. As the dust is transported to the north and over the TP, mass loadings are 5-10 mg m(-2) above a height of 6 km.The dust mass flux carried from East Asia to the TP is 7.9 Tg yr(-1), mostly occurring at heights of 3-6 km. The dust particles from North Africa and the Middle East are transported eastward following the westerly jet and then are carried into the TP at the west side with dust mass fluxes of 7.8 and 26.6 Tg yr(-1), respectively. The maximum mass flux of the North African dust mainly occurs at 0-3 km (3.9 Tg yr(-1)), while the Middle Eastern dust occurs at 69 km (12.3 Tg yr(-1)). The dust outflow occurs on the east side (-17.89 Tg yr(-1)) and south side (11.22 Tg yr(-1)) of the TP, with a peak value (8.7 Tg yr(-1)) at 6-9 km. Moreover, the dust (by mass) is concentrated within the size range of 1.25-5.0 mu m and the dust (by particle number) is concentrated in the size range of 0.156-1.25 mu m. Compared with other aerosols, the dust contributes to more than 50% of the total AOD over the TP. The direct radiative forcing induced by the dust is -1.28 W m(-2) at the top of the atmosphere (cooling), 0.41 W m(-2) in the atmosphere (warming), and -1.68 W m(-2) at the surface (cooling). Our quantitative analyses of the dust contributions from different source regions and the associated radiative forcing can help us to better understand the role of dust on the climate over the TP and surrounding regions.