This study evaluates the impact of assimilating moderate resolution imaging spectroradiometer (MODIS) aerosol optical depth (AOD) data using different data assimilation (DA) methods on dust analyses and forecasts over North Africa and tropical North Atlantic. To do so, seven experiments are conducted using the Weather Research and Forecasting dust model and the Gridpoint Statistical Interpolation analysis system. Six of these experiments differ in whether or not AOD observations are assimilated and the DA method used, the latter of which includes the three‐dimensional variational (3D‐Var), ensemble square root filter (EnSRF), and hybrid methods. The seventh experiment, which allows us to assess the impact of assimilating deep blue AOD data, assimilates only dark target AOD data using the hybrid method. The assimilation of MODIS AOD data clearly improves AOD analyses and forecasts up to 48 hr in length. Results also show that assimilating deep blue data has a primarily positive effect on AOD analyses and forecasts over and downstream of the major North African source regions. Without assimilating deep blue data (assimilating dark target only), AOD assimilation only improves AOD forecasts for up to 30 hr. Of the three DA methods examined, the hybrid and EnSRF methods produce better AOD analyses and forecasts than the 3D‐Var method does. Despite the clear benefit of AOD assimilation for AOD analyses and forecasts, the lack of information regarding the vertical distribution of aerosols in AOD data means that AOD assimilation has very little positive effect on analyzed or forecasted vertical profiles of backscatter.

中文翻译：

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使用不同的数据同化方法评估同化气溶胶光学深度观测值对北非和东大西洋沙尘预报的影响。

这项研究使用不同的数据同化（DA）方法评估了中分辨率成像光谱仪（MODIS）气溶胶光学深度（AOD）数据对北非和热带北大西洋的粉尘分析和预报的影响。为此，使用“天气研究和预报”尘埃模型和Gridpoint统计插值分析系统进行了七个实验。这些实验中的六个实验在是否吸收AOD观测和使用DA方法方面有所不同，后者包括三维变分（3D-Var），集成平方根滤波器（EnSRF）和混合方法。第七个实验使我们能够评估吸收深蓝色AOD数据的影响，使用混合方法仅吸收暗目标AOD数据。MODIS AOD数据的同化可以明显改善AOD分析并预测长达48小时的时间。结果还表明，吸收深蓝色数据对北非主要源区上下游的AOD分析和预报具有主要的积极影响。如果不吸收深蓝色数据（仅吸收暗目标），则AOD吸收最多只能改善AOD预测长达30小时。在检查的三种DA方法中，混合方法和EnSRF方法产生的AOD分析和预测要比3D-Var方法更好。尽管AOD同化对于AOD分析和预报有明显的好处，但是由于缺乏有关AOD数据中气溶胶垂直分布的信息，这意味着AOD同化对反向散射的分析或预测垂直分布几乎没有积极影响。