Abstract. Dust aerosols affect the radiative and energy balance at local and global scales by scattering and absorbing sunlight and infrared light. Parameterizations of dust lifting, microphysics, as well as physical and radiative properties of dust in climate models are still subject to large uncertainty. Here we use a sectional aerosol model (CARMA) coupled with a climate model (CESM1) to investigate the global distribution of dust aerosols, with an emphasis on the vertical distribution of dust. Consistent with observations at locations remote from source regions, simulated dust mass size distributions peak at around 2–3 micrometres in diameter and increase by 4 orders of magnitude from 0.1 μm to 2 µm. The size distribution above 2 µm is highly variable depending on distance from the source, and subject to uncertainty due to possible size dependent changes in physical properties such as shape and density. Simulated annual mean dust mass concentrations are within one order of magnitude of those found by the surface measurement network around the globe. Simulated annual mean aerosol optical depths are ~10 % lower than AERONET observations near the dust source regions. Both simulations and in-situ measurements during the NASA ATom field campaign suggest that dust mass concentrations over the remote ocean drop by two to three orders of magnitude from the surface to the upper troposphere (200 hPa). The model suggests that Saharan, Middle Eastern, and Asian dust accounts for ~59.7 %, 12.5 %, and 13.3 % of the global annual mean dust emissions, with the remaining 14.5 % originating from scattered smaller dust sources. Although Saharan dust dominates global dust mass loading at the surface, the relative contribution of Asian dust increases with altitude and becomes dominant in the upper troposphere. The simulations show that Asian dust contributes ~60.9 % to the global and annual mean dust concentration between 266 hPa and 160 hPa. Asian dust is mostly lifted in the spring by mid-latitude frontal systems. However, deep convection during the Asian summer monsoon (ASM) favours the vertical transport of local dust to the upper atmosphere. Simulated dust accumulates in the ASM anticyclone and forms a local maximum; however, the simulated dust mass concentration is only ~0.04 % of the total aerosols in the Asian Tropopause Aerosol Layer (ATAL), which are dominated by organics, sulfates and nitrates.

中文翻译：

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CESM1/CARMA模拟的亚洲、中东和撒哈拉沙尘全球分布

摘要。尘埃气溶胶通过散射和吸收太阳光和红外光来影响局部和全球范围内的辐射和能量平衡。气候模型中扬尘、微物理以及尘埃的物理和辐射特性的参数化仍然存在很大的不确定性。在这里，我们使用截面气溶胶模型（CARMA）和气候模型（CESM1）来研究尘埃气溶胶的全球分布，重点是尘埃的垂直分布。与在远离源区域的位置的观测结果一致，模拟的尘埃质量大小分布在直径约 2-3 微米处达到峰值，从 0.1 微米到 2 微米增加了 4 个数量级。2 µm 以上的尺寸分布随与源的距离变化很大，并且由于形状和密度等物理特性可能发生的尺寸相关变化而受到不确定性的影响。模拟的年平均尘埃质量浓度与全球地表测量网络发现的浓度相差一个数量级。模拟的年平均气溶胶光学深度比尘埃源区域附近的 AERONET 观测值低约 10%。NASA ATom 野外活动期间的模拟和现场测量都表明，遥远海洋上空的尘埃质量浓度从表面到对流层上层（200 hPa）下降了两到三个数量级。该模型表明，撒哈拉、中东和亚洲的尘埃占全球年平均尘埃排放量的 59.7%、12.5% 和 13.3%，其余 14.5% 来自分散的较小尘埃源。尽管撒哈拉尘埃在全球地表尘埃质量负荷中占主导地位，但亚洲尘埃的相对贡献随着高度的增加而增加，并在对流层上层占主导地位。模拟表明，亚洲尘埃对 266 hPa 至 160 hPa 之间的全球和年平均尘埃浓度的贡献约为 60.9%。亚洲尘埃主要在春季由中纬度锋面系统扬起。然而，亚洲夏季风（ASM）期间的深层对流有利于当地尘埃垂直传输到高层大气。模拟尘埃在 ASM 反气旋中积聚并形成局部最大值；然而，模拟的尘埃质量浓度仅为亚洲对流层顶气溶胶层 (ATAL) 中总气溶胶的约 0.04%，这些气溶胶以有机物、硫酸盐和硝酸盐为主。亚洲尘埃的相对贡献随着高度的增加而增加，并在对流层上层占主导地位。模拟表明，亚洲尘埃对 266 hPa 至 160 hPa 之间的全球和年平均尘埃浓度的贡献约为 60.9%。亚洲尘埃主要在春季由中纬度锋面系统扬起。然而，亚洲夏季风（ASM）期间的深层对流有利于当地尘埃垂直传输到高层大气。模拟尘埃在 ASM 反气旋中积聚并形成局部最大值；然而，模拟的尘埃质量浓度仅为亚洲对流层顶气溶胶层 (ATAL) 中总气溶胶的约 0.04%，这些气溶胶以有机物、硫酸盐和硝酸盐为主。亚洲尘埃的相对贡献随着高度的增加而增加，并在对流层上层占主导地位。模拟表明，亚洲尘埃对 266 hPa 至 160 hPa 之间的全球和年平均尘埃浓度的贡献约为 60.9%。亚洲尘埃主要在春季由中纬度锋面系统扬起。然而，亚洲夏季风（ASM）期间的深层对流有利于当地尘埃垂直传输到高层大气。模拟尘埃在 ASM 反气旋中积聚并形成局部最大值；然而，模拟的尘埃质量浓度仅为亚洲对流层顶气溶胶层 (ATAL) 中总气溶胶的约 0.04%，这些气溶胶以有机物、硫酸盐和硝酸盐为主。模拟表明，亚洲尘埃对 266 hPa 至 160 hPa 之间的全球和年平均尘埃浓度的贡献约为 60.9%。亚洲尘埃主要在春季由中纬度锋面系统扬起。然而，亚洲夏季风（ASM）期间的深层对流有利于当地尘埃垂直传输到高层大气。模拟尘埃在 ASM 反气旋中积聚并形成局部最大值；然而，模拟的尘埃质量浓度仅为亚洲对流层顶气溶胶层 (ATAL) 中总气溶胶的约 0.04%，这些气溶胶以有机物、硫酸盐和硝酸盐为主。模拟表明，亚洲尘埃对 266 hPa 至 160 hPa 之间的全球和年平均尘埃浓度的贡献约为 60.9%。亚洲尘埃主要在春季由中纬度锋面系统扬起。然而，亚洲夏季风（ASM）期间的深层对流有利于当地尘埃垂直传输到高层大气。模拟尘埃在 ASM 反气旋中积聚并形成局部最大值；然而，模拟的尘埃质量浓度仅为亚洲对流层顶气溶胶层 (ATAL) 中总气溶胶的约 0.04%，这些气溶胶以有机物、硫酸盐和硝酸盐为主。亚洲夏季风（ASM）期间的深层对流有利于当地尘埃垂直输送到高层大气。模拟尘埃在 ASM 反气旋中积聚并形成局部最大值；然而，模拟的尘埃质量浓度仅为亚洲对流层顶气溶胶层 (ATAL) 中总气溶胶的约 0.04%，这些气溶胶以有机物、硫酸盐和硝酸盐为主。亚洲夏季风（ASM）期间的深层对流有利于当地尘埃垂直输送到高层大气。模拟尘埃在 ASM 反气旋中积聚并形成局部最大值；然而，模拟的尘埃质量浓度仅为亚洲对流层顶气溶胶层 (ATAL) 中总气溶胶的约 0.04%，这些气溶胶以有机物、硫酸盐和硝酸盐为主。