Potential Driving Factors on Surface Solar Radiation Trends over China in Recent Years

Qiuyan Wang,Martin Wild,Hua Zhang

doi:10.5194/egusphere-egu21-5264

Abstract

&lt;p&gt;The annual mean surface solar radiation (SSR) trends under all-sky, clear-sky, all-sky-no-aerosol, and clear-sky-no-aerosol conditions as well as their possible causes are analyzed during 2005-2018 over China based on different satellite-retrieved datasets to determine the likely drivers of the trends. The results confirm clouds and aerosols as the major contributors to such all-sky SSR trends over China but playing different roles over sub-regions. Aerosol variations during this period result in a widespread brightening, while cloud effects show opposite trends from south to north. Moreover, aerosols contribute more to the increasing all-sky SSR trends over northern China, while clouds dominate the SSR declines over southern China. A radiative transfer model is used to explore the relative contributions of cloud cover from different cloud types to the all-types-of-cloud-cover-induced (ACC-induced) SSR trends during this period in four typical sub-regions over China. The simulations point out that the decreases in low-cloud-cover (LCC) over the North China Plain are the largest positive contributor of all cloud types to the marked annual and seasonal ACC-induced SSR increases, and the positive contributions from both high-cloud-cover (HCC) and LCC declines in summer and winter greatly contribute to the ACC-induced SSR increases over East China. The contributions from medium-low-cloud-cover (mid-LCC) and LCC variations dominate the ACC-caused SSR trends over southwestern and South China all year round, except for the larger HCC contribution in summer.&lt;/p&gt;

Highlights

As an important component of the climate system, solar radiation incident at the Earth’s surface is the primary energy source for life on the planet
The annual and seasonal means of the above driving factors for 14 years are used as inputs into a radiative transfer model to calculate their respective effects on the surface solar radiation (SSR) trends by using a concept of relative SSR trend percentage to avoid discrepancies caused by different model assumptions
This study examines the relative contributions of cloud cover from different cloud types to the simulated ACC-induced SSR trends averaged over four typical regions of China both at annual and seasonal time scales

Summary

Introduction

As an important component of the climate system, solar radiation incident at the Earth’s surface is the primary energy source for life on the planet. It can influence surface temperature, the hydrological cycle, plant photosynthesis and carbon uptake, thereby largely determining our climatic conditions and ecological environment [1–3]. This quantity is not constant at decadal time scales, instead, it has undergone significant decadal variations since the 1950s in many regions of the world, declining until the late. The relative importance of the above-mentioned factors mainly depends on the meteorological conditions or the degree of air pollutions [3,5]

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