Tropospheric aerosols in the Mediterranean: 2. Radiative effects through model simulations and measurements
Tropospheric aerosols in the Mediterranean: 2. Radiative effects through model simulations and measurements
复制标题
地中海对流层气溶胶：2. 通过模型模拟和测量得出的辐射效应
DOI：
10.1029/2002jd002807
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发表时间：
2003
影响因子：
--
通讯作者：
G. Pace
中科院分区：
文献类型：
--
作者：
D. Meloni;A. Sarra;J. Deluisi;T. Iorio;G. Fiocco;W. Junkermann;G. Pace
[1]对地中海兰佩杜萨岛对流层气溶胶的辐射效应进行了研究，方法是比较辐射传输模式的测量结果和结果。利用该模式再现了1999年5月三种无云条件下测量到的紫外线辐照光谱（286.5-363 nm），从而估算了气溶胶特性和直接辐射强迫。观测结果显示，与气团的不同来源有关的气溶胶载荷和分布差异很大：低气溶胶光学深度与来自北大西洋/欧洲的气团有关（5月25日和27日），而来自撒哈拉地区的矿物粉尘观测到高达7公里高度的较大颗粒和较大的光学深度（5月18日）。利用对大气结构和组成的详细描述初始化辐射传输模型。荒漠沙尘在500 nm处的单散射反照率和不对称参数分别在0.73 ~ 0.84和0.75 ~ 0.79之间。辐射传输计算表明，表面紫外线辐照度大于10%的差异可能是由于缺乏对气溶胶大小分布的详细了解造成的。气溶胶也可能增加或减少对流层臭氧的吸收效率，这取决于颗粒的特性。在300-800 nm光谱范围内，对地表和大气顶部的气溶胶直接辐射强迫（TOA）也进行了估算。在5月18日，相对于无气溶胶的大气，气溶胶使地表瞬时向下辐照度分别减少了70.8、37.2和39.1 W m−2 （415 nm处气溶胶光学深度为0.511）、25（0.165）和27（0.224）。地表单位光学深度的辐射强迫最大的是来自北方的大陆/海洋气溶胶。在TOA的强迫是负的，因此在沙漠沙尘的情况下产生冷却，而来自北方的气溶胶接近于零或正。
[1] The radiative effects of tropospheric aerosols at the island of Lampedusa, in the Mediterranean, have been investigated by comparing measurements and results from a radiative transfer model. The model was used to reproduce the measured ultraviolet irradiance spectra (286.5–363 nm) in three cases of cloud-free conditions in May 1999, allowing the estimation of the aerosol properties and of the direct radiative forcing. Observations show very different aerosol loading and distribution, connected to the different origins of the air masses: low aerosol optical depths are associated with air masses from North Atlantic/Europe (25 and 27 May), and larger particles up to 7 km altitude and larger optical depths are observed for mineral dust coming from the Saharan region (18 May). The detailed description of the atmospheric structure and composition was used to initialize the radiative transfer model. The estimated single-scattering albedo and asymmetry parameter at 500 nm for the desert dust are in the range 0.73–0.84 and in the range 0.75–0.79, respectively. Radiative transfer calculations show that differences of the surface ultraviolet irradiance larger than 10% may arise from the lack of a detailed knowledge of the aerosol size distribution. Aerosol may also increase or reduce the absorption effectiveness of tropospheric ozone, depending on the characteristics of the particles. Estimates of the direct aerosol radiative forcing in the spectral range 300–800 nm at the surface and at the top of the atmosphere (TOA) were also derived. At the surface, aerosols produce a decrease of the instantaneous downward irradiance with respect to an aerosol-free atmosphere by 70.8, 37.2, and 39.1 W m−2, for 18 May (the aerosol optical depth is 0.511 at 415 nm), 25 (0.165) and 27 (0.224), respectively. The radiative forcing per unit optical depth at the surface is largest for aerosol of continental/marine origin, transported from North. The forcing at the TOA is negative, thus producing a cooling, in the desert dust case, and close to zero or positive for aerosol originating from North.