Cloud geometry effects on atmospheric solar absorption
Cloud geometry effects on atmospheric solar absorption
复制标题
云几何形状对大气太阳吸收的影响
DOI：
10.1175/1520-0469(2000)057
复制
发表时间：
2000
影响因子：
3.1
通讯作者：
A. Grossman
中科院分区：
文献类型：
--
作者：
Q. Fu;M. Cribb;H. Barker;S. Krueger;A. Grossman
通过将MonteCarlo光子输运算法与Fu‐Liou辐射模型相结合，建立了一个三维宽带太阳辐射传输方案。它适用于热带中尺度对流云和副热带海洋边界层云的二维云解析模式产生的字段。通过将全分辨率蒙特卡罗结果与将平面平行辐射模型应用于每个柱的独立柱近似（伊卡）的结果进行比较，来检查云的几何形状对辐射能量收支的影响。对于热带对流云系，无论太阳天顶角如何，云的几何效应总是增强大气对太阳的吸收。在一个大的水平域（512公里），在domainaveraged大气吸收之间的Monte Carlo和伊卡的差异是小于n4Wm22在白天。然而，对于较小的域（例如，75公里），包含一个集群的深对流塔，域平均吸收可以增强超过20 W m22。对于一个副热带海洋边界层云系统，在层积云过渡，计算表明，伊卡的工作非常好的域平均通量的层积云场，即使是一个非常小的域（4.8公里）。对于信云云场，云边和光子水平传输的影响变得更加显著。还计算了两个云系，包括黑碳气溶胶和水蒸气连续体。结果表明，云的几何形状对黑碳气溶胶和水汽连续体的吸收增强没有明显的影响。目前的研究表明，由于云相关的三维光子传输的大气吸收增强是小的。这种增强不能解释最近研究所提出的过度吸收。
A 3D broadband solar radiative transfer scheme is formulated by integrating a Monte Carlo photon transport algorithm with the Fu‐Liou radiation model. It is applied to fields of tropical mesoscale convective clouds and subtropical marine boundary layer clouds that were generated by a 2D cloud-resolving model. The effects of cloud geometry on the radiative energy budget are examined by comparing the full-resolution Monte Carlo results with those from the independent column approximation (ICA) that applies the plane-parallel radiation model to each column. For the tropical convective cloud system, it is found that cloud geometry effects always enhance atmospheric solar absorption regardless of solar zenith angle. In a large horizontal domain (512 km), differences in domainaveraged atmospheric absorption between the Monte Carlo and the ICA are less tha n4Wm 22 in the daytime. However, for a smaller domain (e.g., 75 km) containing a cluster of deep convective towers, domain-averaged absorption can be enhanced by more than 20 W m22. For a subtropical marine boundary layer cloud system during the stratus-to-cumulus transition, calculations show that the ICA works very well for domain-averaged fluxes of the stratocumulus cloud fields even for a very small domain (4.8 km). For the trade cumulus cloud field, the effects of cloud sides and horizontal transport of photons become more significant. Calculations have also been made for both cloud systems including black carbon aerosol and a water vapor continuum. It is found that cloud geometry produces no discernible effects on the absorption enhancement due to the black carbon aerosol and water vapor continuum. The current study indicates that the atmospheric absorption enhancement due to cloud-related 3D photon transport is small. This enhancement could not explain the excess absorption suggested by recent studies.