Aerosol absorption over the Aegean Sea under northern summer winds
Aerosol absorption over the Aegean Sea under northern summer winds
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DOI：
10.1016/j.atmosenv.2020.117533
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发表时间：
2020-06
影响因子：
5
通讯作者：
Georgia Methymaki;E. Bossioli;J. Kalogiros;G. Kouvarakis;N. Mihalopoulos;A. Nenes;M. Tombrou
中科院分区：
文献类型：
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作者：
Georgia Methymaki;E. Bossioli;J. Kalogiros;G. Kouvarakis;N. Mihalopoulos;A. Nenes;M. Tombrou
在本模拟研究中，除散射外，还研究了爱琴海（地中海东部）上空典型的13天暖期（北风输送污染气团）对辐射的吸收影响。估算了由总吸收引起的模拟（WRF-Chem）强迫以及黑碳（BC）、粉尘和海盐的贡献，分别为1.3、1.2、0.1和接近于零的W m−2。由于粉尘和海盐的影响可以忽略不计，因此主要关注BC。BC吸收使到达地面的向下短波辐照度减少5.2 W m−2，使到达地面的向上短波辐照度减少1.7 W m−2。向下和向上的长波辐照度相应地增加了2.3和1.2 W m−2。尽管在研究期间不利于云的形成，但BC的吸收总体上使云水混合比降低了10%（半直接效应）。然而，在特定的日子和有限的多云地区，半直接效应减少了20%的低层云，而在高层云的情况下，减少幅度高达29%。为了检验半直接效应下的物理机制，对所有模拟的升温速率进行了分析。辐射的直接吸收使空气温度以高达0.2 K day - 1的速率升高，但在表层内部例外，那里出乎意料地盛行长波冷却。表面层的加热主要归因于平流过程，因为更多的加热气团被输送到爱琴海上空。
In this modelling study, the absorption influence on radiation, apart from scattering, is studied above the Aegean Sea (Eastern Mediterranean) under a typical warm 13-day period with northern winds, transporting polluted air masses. The simulated (WRF-Chem) forcing caused by the total absorption is estimated along with black carbon (BC), dust, and sea salt contributions, 1.3, 1.2, 0.1 and nearly zero W m−2, accordingly. As dust and sea salt influence is negligible, the main focus is on BC. BC absorption reduces downward shortwave irradiance reaching the ground by up to 5.2 W m−2and the upward part by up to 1.7 W m−2. The downward and the upward longwave irradiances are augmented by up to 2.3 and 1.2 W m−2, accordingly. Even though the cloud formation is not favoured during the study period, BC absorption reduces overall the cloud water mixing ratio by 10% (semi-direct effect). However, during specific days and over limited cloudy areas, the semi-direct effect reduces low level clouds up to 20% while in case of higher clouds the reduction reaches up to ~29%. In order to examine the physical mechanisms below semi-direct effect, all modelled heating rates are analysed. Radiation direct absorption increases the air temperature with a rate up to 0.2 K day−1, with an exception inside the surface layer, where unexpectedly longwave cooling prevails. The heating of the surface layer is mainly attributed to the advection process, as more heated air masses are transported over the Aegean Sea.