There are large temporal variations in the optical properties and types of aerosols. These are due to the effects of environmental and meteorological conditions, industrial and agricultural influences, and other human influences and natural factors in each ecological functional area. Aerosol optical depth AOD and Ångström exponent AE parameters were extracted from the Moderate Resolution Imaging Spectroradiometer MODIS satellite with a 3 km resolution of MOD04_3K and MYD04_3K. The study covers sixteen selected stations in Horn Africa–Ethiopia with neighboring Eritrea, Djibouti, and South Sudan countries clustered into four regions for the periods of 2001–2022 to obtain detailed information on the temporal behaviors and classification of aerosols in each season. The results show that the temporal variability of AOD and AE values is large, with values ranging from 0.00 to 2.10 and 0.67 to 1.23, with minimum values most likely between December 16 and January 07, and maximum values between June 22 and July 24 for both Terra and Aqua in the southeast and northeast clusters, respectively. The lowest AOD and AE values were most common in the Belg (during September–November) and sometimes in Bega (during December–February), while the highest were in the Kiremt season (during June–August). The minimum values were observed at the Kebri Dahar site, and the maximum were at the Erta Ale site, which belongs to Ethiopia. Appropriate AOD and AE thresholds were used to classify the aerosol types into marine (MR), dust (DS), biomass burning (BB), desert dust (DD), urban (UR), and the residual cases were considered mixture (MX) types. The study concludes that marine aerosols were the most abundant at 47.71%, followed by urban aerosols at 28.29%, while desert dusts, enriched at 14.65%, accounted for the third place with free of dust particles. The Mann–Kendall (MK) statistical trend test was applied to the annual time series in all clustered regions and shows an almost positive increasing variability with a slight decrease in the forward series and vice–versa.

中文翻译：

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使用 MODIS 卫星数据计算非洲之角 - 埃塞俄比亚上空气溶胶的时间分布：第 01 部分


气溶胶的光学特性和类型存在很大的时间变化。这是各生态功能区环境气象条件、工农业影响以及其他人类影响和自然因素的影响。气溶胶光学深度AOD和Ångström指数AE参数是从分辨率为3 km的MOD04_3K和MYD04_3K中分辨率成像光谱仪MODIS卫星中提取的。该研究涵盖2001年至2022年期间非洲之角-埃塞俄比亚的16个选定站点以及邻国厄立特里亚、吉布提和南苏丹，分为四个区域，以获得每个季节气溶胶时间行为和分类的详细信息。结果表明，AOD和AE值的时间变异性较大，值范围为0.00~2.10和0.67~1.23，最小值最有可能出现在12月16日至1月7日之间，最大值出现在6月22日至7月24日之间。 Terra 和 Aqua 分别位于东南部和东北部星团。最低的 AOD 和 AE 值最常见于贝尔格（9 月至 11 月），有时在贝加（12 月至 2 月），而最高值出现在 Kiremt 季节（6 月至 8 月）。最小值出现在 Kebri Dahar 遗址，最大值出现在属于埃塞俄比亚的 Erta Ale 遗址。采用适当的AOD和AE阈值将气溶胶类型分为海洋（MR）、粉尘（DS）、生物质燃烧（BB）、沙漠粉尘（DD）、城市（UR），其余情况视为混合物（MX）类型。研究得出的结论是，海洋气溶胶含量最高，为 47.71%，其次是城市气溶胶，含量为 28.29%，而沙漠尘埃含量丰富，为 14%。65%，无尘埃颗粒占第三位。 Mann-Kendall (MK) 统计趋势检验适用于所有聚类区域的年度时间序列，显示出几乎正的增加变异性，而前向序列略有下降，反之亦然。