Department of Science Technology and Engineering, Kibabii University, P.O. Box 1699-50200, Bungoma, Kenya.
Department of Science Technology and Engineering, Kibabii University, P.O. Box 1699-50200, Bungoma, Kenya.
Sci Total Environ. 2023 Mar 15;864:161041. doi: 10.1016/j.scitotenv.2022.161041. Epub 2022 Dec 21.
East Africa (EA) suffers from the inadequate characterization of atmospheric aerosols, with far-reaching consequences of its inability to quantify precisely the impacts of these particles on regional climate. The current study aimed at characterizing absorption and radiative properties of aerosols using the long-term (2001-2018) AErosol RObotic NETwork (AERONET) and Modern-Era Retrospective analysis for Research and Applications (MERRA-2) data over three environmentally specific sites in EA. The annual mean absorption aerosol optical depth (AAOD), absorption Angstrom Exponent (AAE), total effective radius (R), and total volume concentration (μm/μm) revealed significant spatial heterogeneity over the domain. The study domain exhibited a significant contribution of fine-mode aerosols compared to the coarse-mode particles. The monthly variation in SSA over EA explains the strength in absorption aerosols that range from moderate to strong absorbing aerosols. The aerosols exhibited significant variability over the study domain, with the dominance of absorbing fine-mode aerosols over Mbita accounting for ∼40 to ∼50 %, while weakly absorbing coarse-mode particles accounted for ∼8.2 % over Malindi. The study conclusively determined that Mbita was dominated by AAOD mainly from biomass burning in most of the months, whereas Malindi was coated with black carbon. The direct aerosol radiative forcing (DARF) retrieved from both the AERONET and MERRA-2 models showed strong cooling at the top of the atmosphere (TOA; -6 to -27 Wm) and the bottom of the atmosphere (BOA, -7 to -66 Wm). However, significant warming was noticed within the atmosphere (ATM; +14 to +76 Wm), an indication of the role of aerosols in regional climate change. The study contributed to understanding aerosol absorption and radiative characteristics over EA and can form the basis of other related studies over the domain and beyond.
东非（EA）在大气气溶胶的特征描述方面存在不足，这导致其无法精确量化这些粒子对区域气候的影响，后果严重。本研究旨在利用长期（2001-2018 年）AErosol RObotic NETwork（AERONET）和现代回顾分析研究和应用（MERRA-2）数据，对 EA 三个特定环境地点的气溶胶吸收和辐射特性进行特征描述。该研究域的年度平均吸收气溶胶光学深度（AAOD）、吸收 Angstrom 指数（AAE）、总有效半径（R）和总体积浓度（μm/μm）表现出显著的空间异质性。与粗模态粒子相比，研究域显示出细模态气溶胶的显著贡献。EA 上空的月平均单次散射反照率（SSA）变化解释了从中等吸收到强吸收气溶胶的吸收气溶胶的强度。气溶胶在研究域内表现出显著的可变性，吸收细模态气溶胶在 Mbita 占主导地位，约为 40%至 50%，而在 Malindi 较弱吸收的粗模态粒子占约 8.2%。研究结论确定，Mbita 主要由生物质燃烧产生的 AAOD 主导，大多数月份都是如此，而 Malindi 则覆盖着黑碳。从 AERONET 和 MERRA-2 模型中检索到的直接气溶胶辐射强迫（DARF）在大气层顶（TOA；-6 到-27 Wm）和大气层底（BOA，-7 到-66 Wm）显示出强烈的冷却。然而，在大气层内（ATM；+14 到+76 Wm）观察到明显的变暖，这表明气溶胶在区域气候变化中的作用。本研究有助于了解 EA 上空的气溶胶吸收和辐射特性，并可为该地区及其他地区的其他相关研究提供基础。
