Department of Physics, IMARENAB University of León, 24071 León, Spain.
Université Toulouse III, Laboratoire d'Aérologie UMR 5560, 31400 Toulouse, France.
Sci Total Environ. 2022 May 1;819:152970. doi: 10.1016/j.scitotenv.2022.152970. Epub 2022 Jan 8.
The radiative forcing before and after rain events was studied between 12 February 2016 and 14 March 2017 in León, Spain. For this purpose, the radiative forcing fluxes were calculated using the Radiative Transfer Model Global Atmospheric ModEl (RTM GAME). After the application of a set of selection criteria (based on the availability of AERONET data, rain characteristics and lightning maps), 16 stratiform rain events were identified, concentrated in spring and winter, and 15 convective rain events were found concentrated in spring and summer. Rainfall events were grouped according to the atmospheric forcing (ΔF) before rain: "low" or "high" (lower or higher than 30 W m). The threshold has been set at this value because it is the mean ΔF of all the selected events before rain. There were significant statistical differences between stratiform and convective events in rain duration, mean raindrop diameter and parameters a and b of radar reflectivity Z and rainfall intensity R relationship (Z = a R). When comparing "low" and "high" groups, raindrop diameter was similar in stratiform (0.51 ± 0.08 vs 0.48 ± 0.12 mm) and convective events (0.96 ± 0.98 vs 0.83 ± 0.63 mm), registering higher values for the latter. In stratiform events, the rain scavenging effect on aerosol particles is clearly observed in the "high" group with a decrease of radiative forcing of -27.0 ± 25.3%, and to a lesser extent, in the "low" group, probably because of a lower aerosol load in the atmosphere. In stratiform events, the mode of the raindrop size gamma distribution presented statistical differences between "low" (0.25 ± 0.13 mm) and "high" (0.35 ± 0.05 mm) groups. We claim that this points towards a relationship between radiative forcing before rain and the specific characteristics of rainfall measured at ground level. This study increases our knowledge on the important role of rainwater as a clean agent of the atmosphere and its impact on climate (through radiative forcing).
本研究于 2016 年 2 月 12 日至 2017 年 3 月 14 日在西班牙莱昂研究了雨事件前后的辐射强迫。为此，使用辐射传输模型全球大气模型（RTM GAME）计算了辐射强迫通量。在应用了一套选择标准（基于 AERONET 数据的可用性、雨特性和闪电图）之后，确定了 16 场层状雨事件，主要集中在春季和冬季，发现 15 场对流雨事件主要集中在春季和夏季。根据雨前的大气强迫（ΔF）将降雨事件分组：“低”或“高”（低于或高于 30 W m）。该阈值设定为该值，因为它是所有选定雨事件前的平均ΔF。在雨持续时间、平均雨滴直径和雷达反射率 Z 和雨强 R 关系（Z=aR）的参数 a 和 b 方面，层状和对流事件之间存在显著的统计学差异。在比较“低”和“高”组时，层状雨事件中的雨滴直径相似（0.51±0.08 与 0.48±0.12mm）和对流雨事件（0.96±0.98 与 0.83±0.63mm），后者的数值较高。在层状雨事件中，在“高”组中可以明显观察到气溶胶粒子的雨清除效应，导致辐射强迫降低了-27.0±25.3%，而在“低”组中则降低较少，这可能是由于大气中的气溶胶负荷较低。在层状雨事件中，雨滴大小伽马分布的模式在“低”（0.25±0.13mm）和“高”（0.35±0.05mm）组之间存在统计学差异。我们声称，这表明雨前的辐射强迫与地面测量的降雨的具体特征之间存在关系。本研究增加了我们对雨水作为大气清洁剂及其对气候的影响（通过辐射强迫）的重要作用的认识。
