Impact of Multiple Scattering on Longwave Radiative Transfer Involving Clouds
Impact of Multiple Scattering on Longwave Radiative Transfer Involving Clouds
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DOI：
10.1002/2017ms001117
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发表时间：
2017-12-01
影响因子：
6.8
通讯作者：
Mlawer, Eli J.
中科院分区：
文献类型：
--
作者：
Kuo, Chia-Pang;Yang, Ping;Mlawer, Eli J.
大气环流模式（GCM）被广泛用于估计云对全球能量收支和气候其他方面的影响。由于大气环流模式中涉及的辐射传输计算是昂贵的，它是典型的只考虑吸收，而不是在长波（LW）光谱带的云散射。在这项研究中，由于忽略了云的LW辐射的散射的通量和加热率的偏差进行了量化，使用先进的云光学特性模型，和卫星数据从云气溶胶激光雷达和红外探路者卫星观测（CALIPSO），CloudSat，云和地球的辐射能系统（CERES），和中分辨率成像光谱仪（MODIS）合并产品（CCCM）。从产品中，有关大气和云的信息（微物理和降压光学特性，以及顶部和底部高度）被用来模拟通量和加热率。2010年全球模拟结果表明，LW散射使大气层顶（TOA）向上通量减少2.6 W/m（2），使地面向下通量增加1.2 W/m（2），分别约为TOA和地面LW云辐射效应的10%和5%。区域TOA向上通量偏差高达全球平均向外长波辐射（OLR）的5%。LW散射导致对流层顶约0.018 K/d的冷却和地面约0.028 K/d的加热。此外，在350-500 cm（-1）范围内观测到的冰云OLR总偏差超过40%。总体而言，忽略LW散射的辐射效应与晴空条件下大气CO2加倍的辐射效应相当。
General circulation models (GCMs) are extensively used to estimate the influence of clouds on the global energy budget and other aspects of climate. Because radiative transfer computations involved in GCMs are costly, it is typical to consider only absorption but not scattering by clouds in longwave (LW) spectral bands. In this study, the flux and heating rate biases due to neglecting the scattering of LW radiation by clouds are quantified by using advanced cloud optical property models, and satellite data from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), CloudSat, Clouds and the Earth's Radiant Energy System (CERES), and Moderate Resolution Imaging Spectrometer (MODIS) merged products (CCCM). From the products, information about the atmosphere and clouds (microphysical and buck optical properties, and top and base heights) is used to simulate fluxes and heating rates. One-year global simulations for 2010 show that the LW scattering decreases top-of-atmosphere (TOA) upward flux and increases surface downward flux by 2.6 and 1.2 W/m(2), respectively, or approximately 10% and 5% of the TOA and surface LW cloud radiative effect, respectively. Regional TOA upward flux biases are as much as 5% of global averaged outgoing longwave radiation (OLR). LW scattering causes approximately 0.018 K/d cooling at the tropopause and about 0.028 K/d heating at the surface. Furthermore, over 40% of the total OLR bias for ice clouds is observed in 350-500 cm(-1). Overall, the radiative effects associated with neglecting LW scattering are comparable to the counterpart due to doubling atmospheric CO2 under clear-sky conditions.