Relative Contributions of Clouds and Aerosols to Surface Erythemal UV and Global Horizontal Irradiance in Korea

Jaemin Kim,Ja-Ho Koo,Hanlim Lee,Yun Gon Lee

doi:10.3390/en13061504

Abstract

The attenuating effects of clouds and aerosols on global horizontal irradiance (GHI) and ultraviolet erythemal irradiance (UVER) were evaluated and compared using data from four sites in South Korea (Gangneung, Pohang, Mokpo, and Gosan) for the period 2005–2016. It was found that GHI and UVER are affected differently by various attenuating factors, resulting in an increase in the ratio of UVER to GHI with a decrease in the clearness index of GHI. A comparative analysis of the clearness indices of GHI and UVER identified an almost linear relationship between two transmittances by applying UVER with fixed slant ozone ( UVER 300 ) and there was a latitudinal difference in the relationship. Some nonlinearity remained in this relationship, which suggests a contribution by other factors such as clouds and aerosols. Variations of the UVER 300 ratio to GHI with cloud cover and aerosol optical depth were analyzed. The ratio increased with cloud cover and decreased with aerosol optical depth, indicating that clouds attenuate GHI more efficiently than UVER and that the attenuation by aerosols is greater for UVER than for GHI. A multiple linear regression analysis of the clearness indices of GHI and UVER 300 quantitively demonstrates differences in the radiation-reducing effects of clouds and aerosols, with some regional differences by site that can be attributed to local climatic characteristics in South Korea.

Highlights

Energy from solar radiation sustains Earth’s ecosystems and climate
Ultraviolet radiation can be further divided into three sub-classes by wavelength, with 280–320 nm corresponding to ultraviolet B radiation (UV-B; 280–320 nm) [1]
There is a good correlation between global horizontal irradiance (GHI) and UV erythemal irradiance (UVER)

Summary

Introduction

Energy from solar radiation sustains Earth’s ecosystems and climate. The total solar radiation that reaches the Earth’s surface is defined as global horizontal irradiance (GHI; 290–2800 nm) and is typically divided into ultraviolet, visible, and infrared radiation by wavelength. Ultraviolet radiation (UV; 100–400 nm) can have damaging effects on the human body and ecosystems, and careful monitoring of UV is needed. Ultraviolet radiation can be further divided into three sub-classes by wavelength, with 280–320 nm corresponding to ultraviolet B radiation (UV-B; 280–320 nm) [1]. >90% of UV-B is absorbed by stratospheric ozone, enough radiation reaches the Earth’s surface to cause erythema in human skin. MacKinlay and Diffey [2] developed an erythemal action spectrum based on the biological risk of erythema by wavelength.

Methods

Results

Conclusion