Shortwave radiative closure experiment and direct forcing of dust aerosol over northwestern China
Shortwave radiative closure experiment and direct forcing of dust aerosol over northwestern China
复制标题
西北地区沙尘气溶胶的短波辐射闭合实验与直接强迫
DOI：
10.1029/2011gl049571
复制
发表时间：
2011-12-20
影响因子：
5.2
通讯作者：
Fu, Q.
中科院分区：
文献类型：
--
作者：
Ge, J. M.;Huang, J. P.;Fu, Q.
模拟和观测到的地表太阳漫射通量通常存在令人无法接受的巨大差异。为了准确计算可靠的气溶胶直接辐射强迫（DRF），有必要解决和解决这些差异。我们提出并比较了两种从 MFRSR（多滤光片旋转影带辐射计）观测和 AERONET 产品中获取尘埃气溶胶光学特性的方法。发现 MFRSR 的单散射反照率 (SSA) 值比 AERONET 的单散射反照率 (SSA) 值低 10%。这种差异主要是由于 MFRSR 与 AERONET 检索到的折射率虚部不同。 SBDART模型中使用这两组尘埃气溶胶光学特性来模拟短波通量，并将其与表面观测结果进行比较以进行辐射闭合实验。与观测到的漫射辐照度相比，使用 AERONET 衍生的气溶胶 SSA 进行的漫射模拟可能存在显着差异。使用 MFRSR 衍生的气溶胶光学特性模拟的大气顶部 (TOA) 的 DRF 为正，而使用 AERONET 模拟的 DRF 为负。使用 MFRSR 得到的地表和大气中的 DRF 符号与使用 AERONET 得到的相同，而 MFRSR 的幅度要大得多。这表明，与基于 AERONET 的粉尘气溶胶相比，来自 MFRSR 的具有较高吸收率的粉尘气溶胶会加热气溶胶层，但对表面的冷却作用要大得多，这可能对边界层过程产生重要影响。
Modeled and observed solar diffuse fluxes at the surface usually have unacceptably large discrepancies. It is necessary to address and resolve these discrepancies in order to accurately calculate a reliable aerosol direct radiative forcing (DRF). We present and compare two methods of deriving dust aerosol optical properties from the MFRSR (Multi‐Filter Rotating Shadowband Radiometer) observations and the AERONET products. The single‐scattering albedo (SSA) values from MFRSR are found to be 10% less than those from the AERONET. This difference is mainly due to the different imaginary part of refractive index retrieved by the MFRSR compared to AERONET. These two sets of dust aerosol optical properties are used in the SBDART model to simulate the shortwave fluxes that are compared with the surface observations to perform the radiative closure experiment. The diffuse simulations using the AERONET‐derived aerosol SSA may have significant discrepancies compared with the observed diffuse irradiances. The DRFs at the top of atmosphere (TOA) simulated with the MFRSR‐derived aerosol optical properties are positive while the DRFs with the AERONET are negative. The sign of the DRFs at the surface and in the atmosphere using the MFRSR is the same as those using the AERONET while the magnitudes from the MFRSR are much larger. It indicates that dust aerosols with higher absorption as derived from the MFRSR heat the aerosol layer but cool the surface much more than those based on the AERONET, which may have an important impact on the boundary layer processes.