Determination of Radiative Forcing of Saharan Dust Using Combined Toms and Erbe Data
Determination of Radiative Forcing of Saharan Dust Using Combined Toms and Erbe Data
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使用组合 Toms 和 Erbe 数据确定撒哈拉沙尘的辐射强迫
DOI：
10.1029/2000jd900150
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
C. Weaver
中科院分区：
文献类型：
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作者：
N. C. Hsu;J. Herman;C. Weaver
我们通过将Nimbus-7 TOMS得到的气溶胶信息与1985年2-7月期间NOAA-9 ERBE在大气层顶(TOA)观测到的辐射测量相结合，确定了撒哈拉沙尘气溶胶的直接辐射强迫。在分析中，使用了NOAA-9 HIRS2的云参数和可降水量，以帮助筛选云和水汽。结果表明，在“无云”和“干燥”条件下，受撒哈拉沙尘影响的地区，ERBE TOA出射长波通量与TOMS气溶胶指数之间有很好的相关性。ERBE TOA输出短波通量也与TOMS计算的海洋沙尘负荷有很好的相关性。然而，在1985年NOAA-9 ERBE观测到的太阳天顶角范围内，撒哈拉沙尘气溶胶的计算短波强迫在陆地上非常弱和嘈杂。利用与ERBE和TOMS测量相适应的线性回归，估计了TOA向外通量对气溶胶指数变化的敏感因子。短波和长波的响应与海洋上沙尘负荷的变化的比率大约是2比3，但符号相反。将这些敏感性因子乘以TOMS月平均“晴空”气溶胶指数，也可计算出每月平均“晴空”的撒哈拉沙尘的TOA直接强迫。观测和理论分析都表明，下垫面性质、沙尘层高度、环境湿度和云的存在都对矿物气溶胶引起的TOA直接辐射强迫起着重要作用。
We determine the direct radiative forcing of Saharan dust aerosols by combining aerosol information derived from Nimbus-7 TOMS with radiation measurements observed at the top of atmosphere (TOA) by NOAA-9 ERBE made during February-July 1985. Cloud parameters and precipitable water derived from NOAA-9 HIRS2 were used to aid in screening for clouds and water vapor in the analyses. Our results indicate that under “cloud-free” and “dry” conditions there is a good correlation between the ERBE TOA outgoing longwave fluxes and the TOMS aerosol index measurements over both land and ocean in areas under the influence of airborne Saharan dust. The ERBE TOA outgoing shortwave fluxes were also found to correlate well with the dust loading derived from TOMS over ocean. However, the calculated shortwave forcing of Saharan dust aerosols is very weak and noisy over land for the range of solar zenith angle viewed by the NOAA-9 ERBE in 1985. Sensitivity factors of the TOA outgoing fluxes to changes in aerosol index were estimated using a linear regression fit to the ERBE and TOMS measurements. The ratio of the shortwave-to-longwave response to changes in dust loading over the ocean is found to be roughly 2 to 3 but opposite in sign. The monthly averaged “clear-sky” TOA direct forcing of airborne Saharan dust was also calculated by multiplying these sensitivity factors by the TOMS monthly averaged “clear-sky” aerosol index. Both the observational and theoretical analyses indicate that the underlying surface properties, dust layer height, ambient moisture content, and the presence of cloud all play important roles in determining the TOA direct radiative forcing due to mineral aerosols.