非洲地区大气气溶胶光学厚度时空变化及亚速尔高压对沙尘越大西洋传输的影响

研究了非洲地区大气气溶胶光学厚度（AOD）的时空变化及沙尘气溶胶越大西洋海区的传输。结果表明：1）源于撒哈拉沙漠的沙尘及其随赤道东风向西输送使得沙尘气溶胶成为非洲沙漠地区和紧邻的大西洋海区的主要气溶胶组分；AOD高值区和沙尘气溶胶光学厚度高值区在1—7月随赤道辐合带北移同步向北移动，而在8—12月则向南回撤。2）刚果盆地大气气溶胶主要为热带雨林和稀树草原排放的有机碳（OC）和黑碳（BC）气溶胶；其中与生物质燃烧源排放有关的OC、BC高值主要集中在干季（6—9月）的后半段（8—9月）；而生物源OC排放全年连续，其排放峰值出现于雨季开始时；生物质燃烧排放高值期与生物源排放高值期前后相继，形成干季（尤其是后半段）时期的OC、BC光学厚度高值。3）亚马逊河入海口地区主要气溶胶组分为海盐气溶胶，9—11月该区风力输送增强，风向由东南风转变为东风，海盐进入亚马逊河入海口处，形成AOD和海盐气溶胶光学厚度高值区。4）撒哈拉沙漠沙尘气溶胶向大西洋传输的偏北月份为7—9月、偏南月份为1—3月；2000—2016年海区沙尘气溶胶的传输路径存在向南移动的变化趋势，与同期亚速尔高压的增强和沙尘传输路径以北北风分量的增强以及赤道辐合带的移动一致。上述研究结果揭示了利用大气气溶胶时空变化特征反映区域大气环流和气候变化的可能性。

Spatial-temporal variation of aerosol optical depth over Africa and influence of the Azores High on the trans-Atlantic dust transport

The spatial and temporal distribution of the atmospheric aerosol optical depth (AOD) over Africa and the trans-Atlantic transport of the dust aerosol are analyzed using Moderate Resolution Imaging Spectroradiometer (MODIS) AOD products and Modern Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2) reanalysis data. The results are as follows. 1) Dust aerosol is the major aerosol component over the desert areas of Africa and the adjacent Atlantic Ocean due to the dust from the Sahara Desert and its trans-Atlantic transport. Accompanied with the northward shift of the Intertropical Convergence Zone (ITCZ) from January to July are the synchronous northward shift of the high AOD area and the high dust aerosol optical depth (dust AOD) area; in contrast, the ITCZ, the high AOD, and the high dust AOD area retreat southward from August to December. 2) The atmospheric aerosols over the Congo Basin are mainly the organic carbon (OC) and black carbon (BC) originated from the tropical rainforest and the savanna. While the high OC and BC resulting from biomass burning are mainly concentrated in the later half stage (from August to September) of the dry season (from June to September), the biogenic OC emissions are continuous throughout the year with a peak appearing at the beginning of the rainy season. The emission from biomass burning and the emission from biogenic emission occur successively, resulting in a high OC AOD and high BC AOD period during the dry season (especially the latter half stage). 3) The sea salt aerosol is the major aerosol component over the estuary region of the Amazon River; the wind strengthens from September to November over there with a wind direction shift from southeasterly to easterly, which is more favorable for the westward transport of the sea salt aerosol into the estuary region of the Amazon River, resulting in a high AOD and high sea salt AOD region over the adjacent area. 4) The trans-Atlantic(westward) transport of dust aerosol from the Sahara Desert is located northmost from July to September but southmost from January to March. The transport pathways of the dust aerosol over the ocean show a southward shift from 2000 to 2016, which is consistent with the concurrent strengthening of the Azores High (reflected by a decrease of the Ertel''s potential vorticity at 850 hPa and an increase of the geopotential height at 500 hPa) and the strengthening of the north wind to the north of the dust plumes as well as the concurrent shift of the ITCZ. These results suggest a possibility of evaluating the regional atmospheric circulation and climate change using signals from variation and characteristic of the spatial-temporal distribution of atmospheric aerosols.