In this study, we investigate the characteristics of global horizontal irradiance enhancement events induced by clouds over Thessaloniki for the period 1994–2023 using data recorded every one minute. We identified the cloud enhancement (CE) events by creating an appropriate cloud-free irradiance reference using a radiative transfer model and aerosol optical depth data from a collocated Cimel sun photometer and a Brewer spectrophotometer. We found a trend in CE events of +112±35cases/year, and a trend in the corresponding irradiation of +329.9±112.0kJ/year. To our knowledge, such long-term changes in CE events have not been presented in the past. The peak of the CE events was observed during May and June. CE events with duration longer than 10 min are very rare (<8%), with exceptions lasting over an hour and up to 140 min. Finally, we have detected enhancements above the total solar irradiance at the top of the atmosphere for the same solar zenith angle of up to 204W/m2, with the 75 % of the cases below 40W/m2. Most of these extreme events occur in spring – early summer, with a secondary peak in autumn.

中文翻译：

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希腊塞萨洛尼基全球太阳辐照度 30 年记录中的云增强事件分析


在这项研究中，我们使用每分钟记录一次的数据，研究了 1994 年至 2023 年期间塞萨洛尼基上空云层引起的全球水平辐照度增强事件的特征。我们通过使用辐射传输模型和来自并置的 Cimel 太阳光度计和 Brewer 分光光度计的气溶胶光学深度数据创建适当的无云辐照度参考来确定云增强 （CE） 事件。我们发现 CE 事件的趋势为 +112±35 例/年，相应的照射趋势为 +329.9±112.0kJ/年。据我们所知，CE 事件中的这种长期变化在过去从未出现过。CE 事件的高峰期出现在 5 月和 6 月。持续时间超过 10 分钟的 CE 事件非常罕见 （<8%），例外情况持续时间超过 1 小时，最长可达 140 分钟。最后，我们在大气层顶部检测到，对于高达 204W/m2 的相同太阳天顶角，大气层总辐照度以上的增强，其中 75% 的情况低于 40W/m2。这些极端事件大多发生在春季至初夏，其次高峰在秋季。