The comparative analysis of the intra- and interannual dynamics between the Direct Normal Irradiation (DNI) under clear sky conditions and five aerosol types (Dust, Sea Salt, Black Carbon, Organic Carbon, and Sulfate) is the purpose of this study. To achieve this aim, we used fifteen-year DNI and aerosols data downloaded at 3-hour time intervals in nine defined zones throughout Cameroon. The wavelet transform is a powerful tool for studying local variability of amplitudes in a temporal dataset and constitutes our principal tool. The results show unequal distribution of aerosol types according to zones, but the Desert Dusts (DU) and Organic Carbon (OM) aerosols have been found as dominant particles in the studied region. The wavelet coherence analysis between DNI and each aerosol type reveals three bands of periodicity: 4-month band, 8–16-month band, and sometimes after-32-month band, with the most important frequency at 8–16-month band period. However, the intensity of coherence across bands varies with respect to aerosol type as well as each of the nine climate zones. A significant anticorrelation relationship was obtained between DNI and each type of aerosol, emphasizing that the presence of such atmospheric particles could dampen the renewable energy utilized by power systems. Also, the analysis shows that scattering aerosols such as Sulfate and Sea Salt (SU and SS, respectively) lead DNI in phase while absorbing aerosols such as Organic Carbon, Black Carbon, and Dust (OM, BC, and DU, respectively) give phase lag with DNI.

中文翻译：

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喀麦隆大气气溶胶类型与直接辐照关系的小波分析

本研究的目的是对比分析晴空条件下的直接法向辐照（DNI）与五种气溶胶类型（尘埃、海盐、黑碳、有机碳和硫酸盐）之间的年内和年际动态。为了实现这一目标，我们使用了 15 年的 DNI 和以 3 小时的时间间隔在喀麦隆的九个特定区域下载的气溶胶数据。小波变换是研究时间数据集中振幅局部可变性的强大工具，是我们的主要工具。结果显示气溶胶类型根据区域分布不均，但已发现沙漠尘埃（DU）和有机碳（OM）气溶胶是研究区域的主要颗粒。DNI 和每种气溶胶类型之间的小波相干分析揭示了三个周期性波段：4 个月频带、8-16 个月频带，有时是 32 个月后频带，最重要的频率在 8-16 个月频带期间。然而，跨波段的相干强度因气溶胶类型以及九个气候区中的​​每一个而异。在 DNI 和每种类型的气溶胶之间获得了显着的反相关关系，强调这种大气颗粒的存在会抑制电力系统利用的可再生能源。此外，分析表明，散射气溶胶如硫酸盐和海盐（分别为 SU 和 SS）导致 DNI 同相，而吸收如有机碳、黑碳和粉尘（分别为 OM、BC 和 DU）等气溶胶产生相滞后于 DNI。