Comparing two years of Saharan dust source activation obtained by regional modelling and satellite observations
Comparing two years of Saharan dust source activation obtained by regional modelling and satellite observations
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DOI：
10.5194/acp-13-2381-2013
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发表时间：
2012-10
影响因子：
6.3
通讯作者：
I. Tegen;K. Schepanski;B. Heinold
中科院分区：
文献类型：
--
作者：
I. Tegen;K. Schepanski;B. Heinold
采用区域尺度沙尘模式模拟了2007年和2008年撒哈拉沙尘排放和大气分布。模型结果与地球同步气象卫星第二代（MSG）卫星红外尘埃指数图像编制的尘源激活事件进行了比较。观测到的沙源激活频率的早晨最大值表明夜间低空急流的破坏是撒哈拉沙源激活的重要机制。对比结果表明，与观测值相比，模型中粉尘排放开始的时间有所延迟。此外，该模式还低估了与夜间低空急流相关的山区粉尘排放事件的模拟次数。MSG沙尘指数观测表明，2008年沙尘源激活频率较2007年明显增加。这两年之间的差异在模型中不太明显。对尘埃光学厚度的观测，例如在AERONET太阳光度计网的观测站，没有显示出这种增加，这与模式的结果一致。这表明，观测到的粉尘激活事件的数量对于估计撒哈拉沙漠的实际粉尘排放通量只有有限的用处。利用模式重现撒哈拉沙尘年际变化的能力仍然是理解大气沙尘负荷控制的一个重要挑战。
A regional-scale dust model is used to simulate Saharan dust emissions and atmospheric distributions in the years 2007 and 2008. The model results are compared to dust source activation events compiled from infrared dust index imagery from the geostationary Meteosat Second Generation (MSG) satellite. The observed morning maximum in dust source activation frequencies indicates that the breakdown of nocturnal low level jets is an important mechanism for dust source activation in the Sahara. The comparison shows that the time of the day of the onset of dust emission is delayed in the model compared to the observations. Also, the simulated number of dust emission events associated with nocturnal low level jets in mountainous regions is underestimated in the model. The MSG dust index observations indicate a strong increase in dust source activation frequencies in the year 2008 compared to 2007. The difference between the two years is less pronounced in the model. Observations of dust optical thickness, e.g. at stations of the sunphotometer network AERONET, do not show such increase, in agreement with the model results. This indicates that the number of observed dust activation events is only of limited use for estimating actual dust emission fluxes in the Sahara. The ability to reproduce interannual variability of Saharan dust with models remains an important challenge for understanding the controls of the atmospheric dust load.