EGU24-387, updated on 08 Mar 2024
https://doi.org/10.5194/egusphere-egu24-387
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Data-driven Estimation of Cloud Effects on Surface Irradiance atXianghe, a Suburban Site on the North China Plain

Mengqi Liu1, Jinqiang Zhang1,2, Hongrong Shi2, Disong Fu2, and Xiangao Xia2
Mengqi Liu et al.
  • 1Key Laboratory of Atmospheric Sounding, Chengdu University of Information Technology, Chengdu, China
  • 2Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China

Clouds are a dominant modulator of the energy budget. The cloud shortwave radiative effect at the surface (CRE) is closely related to the cloud macro- and micro-physical properties. Systematic observation of surface irradiance and cloud properties are needed to narrow uncertainties in CRE. In this study, 1-min irradiance and Total Sky Imager measurements from 2005 to 2009 at Xianghe in North China Plain are used to estimate cloud types, evaluate cloud fraction (CF), and quantify the sensitivities of surface irradiance with respect to changes in CF whether clouds obscure the sun or not. The annual mean CF is 0.50, further noting that CF exhibits a distinct seasonal variation, with a minimum in winter (0.37) and maximum in summer (0.68). Cumulus occurs more frequently in summer (32%), which is close to the sum of the occurrence of stratus and cirrus. The annual CRE is –54.4 W m–2, with seasonal values ranging from –29.5 W m–2 in winter and –78.2 W m–2 in summer. When clouds do not obscure the sun, CF is a dominant factor affecting diffuse irradiance, which in turn affects global irradiance. There is a positive linear relationship between CF and CRE under sun-unobscured conditions, the mean sensitivity of CRE for each CF 0.1 increase is about 1.2 W m–2 [79.5° < SZA (Solar Zenith Angle) < 80.5°] to 7.0 W m–2 (29.5° < SZA < 30.5°). When clouds obscure the sun, CF affects both direct and diffuse irradiance, resulting in a non-linear relationship between CF and CRE, and the slope decreases with increasing CF. It should be noted that, although only data at Xianghe is used in this study, our results are representative of neighboring areas, including most parts of the North China Plain.

How to cite: Liu, M., Zhang, J., Shi, H., Fu, D., and Xia, X.: Data-driven Estimation of Cloud Effects on Surface Irradiance atXianghe, a Suburban Site on the North China Plain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-387, https://doi.org/10.5194/egusphere-egu24-387, 2024.