Measurements and cloudiness influence on UV radiation in Central China

Abstract

ABSTRACT:Measurements of global solar radiation (G) and ultraviolet (UV) radiation on a horizontal plane at Wuhan, China during 2006-2012 were reported in this study to reveal their hourly, daily and monthly variations. The influences of clouds on UV irradiation and UV/G ratio at different solar elevations were investigated. It was discovered that hourly UV irradiation decreased with cloudiness and UV/G increased with cloud cover, especially for cloudiness greater than 4 octas, which indicated that cloud effects on UV irradiances were more evident in overcast skies. Clearness index (Kt) and UV clearness index (Kuv) was used for characterizing the cloudiness, hourly dependence of UV/G ratio on Kt and complete features of monthly average hourly UV/G were analysed for studying the relationships between G and UV irradiations under different sky conditions. It was revealed that UV/G changed from 4.3% (hourly basis) and 4.4% (daily basis) under overcast skies to 3.8% (hourly basis) and 3.9% (daily basis) in clear skies. It was also observed a largest predominance (90.8%) for the interval 2.8% ≤ UV/G ≤ 5.6% with an average value being about 4.1% during the whole study period. Specific days were selected to further study the cloudiness influence on UV/G, a general daily pattern with lower values during sunrise/sunset and higher values around noon was observed. In addition, the relationship between Kuv and Kt at different solar elevations has been evaluated in detail, Kuv was about 65.8% of Kt during the study period. Finally, using the monthly evolution of the 10-day Kt averages for the UV range, the attenuation of UV radiation in Central China caused by clouds ranged between 65 and 31% in January and July, respectively.

Comparison of different UV models for cloud effect study

“…UV irradiation under any sky conditions can then be estimated from Y-UVc model by considering the K t as a modulation factor [30,41]. The most appropriate relationship (Y-UV1) between UV, UV C and K t can be expressed as:…”

“…Several authors also studied the main factors influencing the UV radiation: Guarnieri et al [39] analyzed the ozone influences; Borkowski [40] investigated the relationship between UV and G and its dependence on total ozone column, cloudiness and aerosol at different scales. Although our earlier studies Wang et al [41] attempted to evaluate cloudiness influence on UV radiation in Central China, UV model should be further tested and calibrated at other regions. There are relatively less studies focusing on quantitatively analyzing the cloudiness effect on UV radiation in large areas of China.…”

Spatio-Temporal Characteristics in the Clearness Index Derived from Global Solar Radiation Observations in Korea

“…These include models for ultraviolet radiation [10][11][12][13][14][15], erythemal ultraviolet radiation [16][17][18][19], photosynthetically active radiation (PAR) [20][21][22], and near-infrared radiation [23]. Using these models, the effects of several atmospheric parameters on the transmission of solar radiation have been assessed, including cloud cover [14,16,24,25], the presence of aerosols [9,26,27], and ozone concentration [12,19]. Additionally, studies of solar energy utilization systems and renewable energy have been performed in which regional K T values were examined to determine the level of solar radiation availability [28,29].…”

UVvariability in an arid region of Northwest China from measurements and reconstructions

“…Moreover, reconstruction of UV radiation during the last decades has gained scientific interest with respect to the well‐known evolution of ozone layer and the general variation of climate (Fioletov et al ., ; Kvalevag et al ., ; Wang et al ., ). Although Wei et al .…”

“…Moreover, reconstruction of UV radiation during the last decades has gained scientific interest with respect to the well-known evolution of ozone layer and the general variation of climate (Fioletov et al, 2001;Kvalevag et al, 2009;Wang et al, 2013b). Although Wei et al (2006) have studied the long-term relationship between UV radiation and ozone in China using Total Ozone Mapping Spectrometer (TOMS) products, our earlier studies (Hu et al, 2010a;Wang et al, 2013a) have studied the interannual variations of UV radiation in Beijing and Wuhan during the past 50 years; Hu et al (2010c) has preliminarily analysed the characteristics of UV radiation in arid and semi-arid regions of China, there is no more studies focusing on analysing the long-term trends of UV radiation in Northwest China, which make it necessary for developing efficient models for investigating UV variability in this area.…”