The Influence of Fine-Mode Aerosols on MODIS–AERONET Aerosol Optical Depth Disparities in the Sahel West Africa

IF 1.6 4区环境科学与生态学 Q4 ENVIRONMENTAL SCIENCES

Aerosol Science and Engineering Pub Date : 2023-03-16 DOI:10.1007/s41810-023-00177-6

Okechukwu K. Nwofor, Anthony A. Uroh, Chukwuma Anoruo

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Abstract

In the present paper, the disparities between aerosol optical depths (AOD) retrieved using the Moderate Resolution Infrared Spectro-radiometer (MODIS) and AErosol RObotic NETwork (AERONET) are presented for five Sahel sites based on the R² correlation metric of their multiyear data. The sites are Banizoumbou (13.54N; 2.66E), Dakar (14.39N; 16.95 W), Djougou (9.76N; 1.59E), Ilorin (8.32N; 4.34E), and Ouagadougou (12.2N; 1.4 W). The overall and seasonal MODIS–AERONET AOD disparities for the locations were evaluated and compared with aerosol parameters associated with fine-mode prevalence at the sites, namely, total AOD (AOD_500nm), precipitable water (PW), Angstrom derivative (α¹), and fine mode fraction (FMF) for the seasons MAM, JJA, SON, and DJF. The largest overall disparity (least R²) was found for Ilorin (R² = 0.021 ± 0.295), while the least overall disparity (largest R²) was found for Banizoumbou (R² = 0.660 ± 0.132). The FMF was found to have the strongest correlations with the overall and seasonal disparities (R²*FMF = – 0.626 (overall), R²*FMF = – 0.350 (MAM), R²*FMF = – 0.9 (JJA), R²*FMF = – 0.602 (SON), R²*FMF = 0.084 (DJF). The largest seasonal disparity occurred at Ilorin in JJA (R² = 0.014) when very low AOD_500nm (0.352) was associated with significant fine-mode occurrence (α¹ = 0.433; FMF = 0.581), while the least seasonal disparity occurred in Djougou in MAM (R² = 0.866) when very high AOD_500nm (0.814) was associated with the least fine-mode occurrence (α¹ ~ 0.00; FMF = 0.278). In Banizoumbou, Dakar, Djougou, and Ouagadougou, fine-mode aerosols occurred more significantly in the dry period (low PW), suggesting a biomass burning source, and at Ilorin, the fine-mode occurred more significantly in the monsoon season (high PW), suggesting a non-biomass burning source. Since the AOD at Ilorin correlated strongest with monsoon-season meridional wind (AOD_500nm*MW_wet = 0.611), compared to other seasonal wind fields, it is inferred that the large monsoon-season MODIS–AERONET AOD disparities at the site were due to southwesterly wind, which transports fine-mode aerosols from coastal industrial sites, as indicated in previous studies.

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精细模式气溶胶对西非萨赫勒地区MODIS-AERONET气溶胶光学深度差的影响

在本文中，基于萨赫勒地区五个站点多年数据的R2相关度量，介绍了使用中分辨率红外光谱辐射计（MODIS）和aerosol RObotic网络（AERONET）检索的气溶胶光学深度（AOD）之间的差异。这些地点分别为Banizoumbou（13.54N；2.66E）、Dakar（14.39N；16.95W）、Djougou（9.76N；1.59E）、Ilorin（8.32N；4.34E）和瓦加杜古（12.2N；1.4W）。评估了这些地点的总体和季节性MODIS–AERONET AOD差异，并将其与这些地点的精细模式流行率相关的气溶胶参数进行了比较，即MAM、JJA、SON和DJF季节的总AOD（AOD500nm）、可降水量（PW）、Angstrom导数（α1）和精细模式分数（FMF）。Ilorin的总体差异最大（R2最小）（R2 = 0.021 ± 0.295），而Banizoumbou的总体差异最小（R2最大） = 0.660 ± 0.132）。FMF与总体和季节差异的相关性最强（R2*FMF = – 0.626（总体），R2*FMF = – 0.350（MAM），R2*FMF = – 0.9（JJA），R2*FMF = – 0.602（儿子），R2*FMF = 0.084（DJF）。最大的季节差异发生在JJA的Ilorin（R2 = 0.014），当非常低的AOD500nm（0.352）与显著的精细模式发生（α1 = 0.433；FMF = 0.581），而MAM中季节差异最小的是焦沟（R2 = 0.866），当非常高的AOD500nm（0.814）与最小精细模式发生（α1 ~ 0.00；FMF = 0.278）。在Banizoumbou、Dakar、Djougou和瓦加杜古，细模式气溶胶在干旱期（低PW）出现得更为显著，表明存在生物质燃烧源，而在Ilorin，细模式在季风季节（高PW）发生得更为明显，表明存在非生物质燃烧源。由于伊洛林的AOD与季风季节经向风的相关性最强（AOD500nm*MWwet = 0.611），与其他季节性风场相比，可以推断，该场地的季风季节MODIS–AERONET AOD差异较大是由于西南风，如先前的研究所示，西南风从沿海工业场地输送精细模式气溶胶。

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来源期刊

Aerosol Science and Engineering Environmental Science-Pollution

CiteScore

3.00

自引率

7.10%

发文量

期刊介绍： ASE is an international journal that publishes high-quality papers, communications, and discussion that advance aerosol science and engineering. Acceptable article forms include original research papers, review articles, letters, commentaries, news and views, research highlights, editorials, correspondence, and new-direction columns. ASE emphasizes the application of aerosol technology to both environmental and technical issues, and it provides a platform not only for basic research but also for industrial interests. We encourage scientists and researchers to submit papers that will advance our knowledge of aerosols and highlight new approaches for aerosol studies and new technologies for pollution control. ASE promotes cutting-edge studies of aerosol science and state-of-art instrumentation, but it is not limited to academic topics and instead aims to bridge the gap between basic science and industrial applications. ASE accepts papers covering a broad range of aerosol-related topics, including aerosol physical and chemical properties, composition, formation, transport and deposition, numerical simulation of air pollution incidents, chemical processes in the atmosphere, aerosol control technologies and industrial applications. In addition, ASE welcomes papers involving new and advanced methods and technologies that focus on aerosol pollution, sampling and analysis, including the invention and development of instrumentation, nanoparticle formation, nano technology, indoor and outdoor air quality monitoring, air pollution control, and air pollution remediation and feasibility assessments.