Drought is an extreme hydroclimate event that has been shown to cause an increase in surface fine dust near source regions, yet the drought–dust relationship in regions predominantly influenced by long-range-transported dust such as the southeastern USA (SEUS) has received less attention. Using long-term surface fine-dust observations, the weekly US Drought Monitor (USDM), and the monthly standardized precipitation–evapotranspiration index (SPEI), this study unmasks spatial disparity in drought–dust relationships in the contiguous USA (CONUS) where the SEUS shows a decrease in surface dust concentrations during drought in contrast to the expected increase in dust found in other CONUS regions. Surface fine dust was found to decrease by ∼ 0.23 µg m⁻³ with a unit decrease in SPEI in the SEUS, as opposed to an increase of ∼ 0.12 µg m⁻³ in the west. The anomalies of dust elemental ratios, satellite aerosol optical depth (AOD), and dust extinction coefficients suggest that both the emissions and trans-Atlantic transport of African dust are weakened when the SEUS is under droughts. Through the teleconnection patterns of the negative North Atlantic Oscillation (NAO), a lower-than-normal and more northeastward displacement of the Bermuda High (BH) is present during SEUS droughts, which results in less dust being transported into the SEUS. At the same time, enhanced precipitation in the Sahel associated with the northward shift of the Intertropical Convergence Zone (ITCZ) leads to lower dust emissions therein. Of the 10 selected models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6), GISS-E2-1-G was found to perform the best in capturing the drought–dust sensitivity in the SEUS. This study reveals the mechanism of how droughts influence aerosol abundance through changing long-range transport of dust.

中文翻译：

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夏季美国东南部干旱导致地表细尘减少：观测和 CMIP6 模型模拟

干旱是一种极端的水文气候事件，已被证明会导致源区附近的地表细尘增加，但在美国东南部 (SEUS) 等主要受远距离传输尘埃影响的地区，旱-尘关系受到的影响较少注意力。使用长期地表细尘观测、每周美国干旱监测 (USDM) 和每月标准化降水-蒸散指数 (SPEI)，本研究揭示了美国毗邻地区 (CONUS) 干旱-沙尘关系的空间差异。 SEUS 显示干旱期间地表尘埃浓度降低，而其他美国大陆地区发现的尘埃预期增加。发现表面微尘减少了∼  0.23  µ g m ^-3SEUS 中 SPEI 减少一个单位，而不是增加∼  0.12  µ g m ^-3在西方。沙尘元素比、卫星气溶胶光学深度（AOD）和沙尘消光系数的异常表明，当 SEUS 处于干旱状态时，非洲沙尘的排放和跨大西洋运输均减弱。通过负北大西洋涛动 (NAO) 的遥相关模式，在 SEUS 干旱期间，百慕大高压 (BH) 的位移低于正常水平且更向东北移动，这导致输送到 SEUS 的灰尘减少。与此同时，与热带辐合带 (ITCZ) 北移相关的萨赫勒地区降水增加导致其中的粉尘排放减少。在参与耦合模型比对项目（CMIP6）第六阶段的 10 个选定模型中，发现 GISS-E2-1-G 在捕捉 SEUS 中的干旱-沙尘敏感性方面表现最好。这项研究揭示了干旱如何通过改变尘埃的远距离传输来影响气溶胶丰度的机制。