Overview of the Atmospheric Brown Cloud East Asian Regional Experiment 2005 and a study of the aerosol direct radiative forcing in east Asia
Overview of the Atmospheric Brown Cloud East Asian Regional Experiment 2005 and a study of the aerosol direct radiative forcing in east Asia
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DOI：
10.1029/2007jd009009
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发表时间：
2007-12-29
影响因子：
4.4
通讯作者：
Schutgens, Nick
中科院分区：
文献类型：
--
作者：
Nakajima, Teruyuki;Yoon, Soon-Chang;Schutgens, Nick
本文介绍了2005年3 - 4月在东亚地区进行的国际区域试验——东亚区域试验2005 (EAREX 2005)，作为联合国环境规划署大气褐云（ABC）项目第一阶段的区域试验之一，讨论了东亚地区气溶胶特征及其直接辐射强迫的一些突出特征，并与另一个ABC早期区域试验的结果进行了比较。ABC马尔代夫季风试验（APMEX）在南亚地区进行。气溶胶光学厚度（AOT）、单散射反照率（SSA）、气溶胶消光截面剖面和CO浓度的时间序列表明，EAREX区域每5 ~ 7 d输送一次空气污染物和矿物粉尘，产生700 nm波长0.86 ~ 0.96的SSA值和500 nm波长60 ~ 90 W m（-2）的晴空短波强迫效率，但由于评估方法的不同，存在一些无法解释的不一致。2005年3月EAREX区域模拟的全天空总强迫在TOA为-1 ~ -2 W m(-2)，在地面为-2 ~ -10 W m(-2)，其量级小于APMEX区域，主要原因是该区域的云分数大（ISCCP总云分数中Gosan为0.70，而Hanimadhoo为0.51）。我们认为可能由于高估了模拟云量和气溶胶尺度高度而低估了强迫。另一方面，模拟地表反照率中可能存在的误差可能导致对陆地上的强迫强度估计过高。我们还提出了短波辐射强迫的简单公式，以了解气溶胶参数和地表条件在确定气溶胶强迫中的作用。这些简单的公式对于检验观测量之间的一致性是有用的。
This article introduces an international regional experiment, East Asian Regional Experiment 2005 (EAREX 2005), carried out in March-April 2005 in the east Asian region, as one of the first phase regional experiments under the UNEP Atmospheric Brown Cloud (ABC) project, and discusses some outstanding features of aerosol characteristics and its direct radiative forcing in the east Asian region, with some comparison with the results obtained in another ABC early phase regional experiment, ABC Maldives Monsoon Experiment (APMEX) conducted in the south Asian region. Time series of aerosol optical thickness (AOT), single scattering albedo (SSA), aerosol extinction cross section profile and CO concentration shows that air pollutants and mineral dust were transported every 5 to 7 days in the EAREX region to produce SSA values at wavelength of 700 nm from 0.86 to 0.96 and large clear-sky shortwave forcing efficiency at 500 nm from 60 W m(-2) to 90 W m(-2), though there are some unexplained inconsistencies depending on the evaluation method. The simulated whole-sky total forcing in the EAREX region is -1 to -2 W m(-2) at TOA and -2 to -10 W m(-2) at surface in March 2005 which is smaller in magnitude than in the APMEX region, mainly because of large cloud fraction in this region (0.70 at Gosan versus 0.51 at Hanimadhoo in the ISCCP total cloud fraction). We suggest there may be an underestimation of the forcing due to overestimation of the simulated cloudiness and aerosol scale height. On the other hand, the possible error in the simulated surface albedo may cause an overestimation of the magnitude of the forcing over the land area. We also propose simple formulae for shortwave radiative forcing to understand the role of aerosol parameters and surface condition to determine the aerosol forcing. Such simple formulae are useful to check the consistency among the observed quantities.