Variation trend of direct and diffuse radiation in China over recent 50 years

Abstract

Using the direct and diffuse solar radiation data during 1961—2009 from 14 stations and during 1961—1991 from 49 stations in China, and the method of linear regression (taken time as an independent variable), wavelet analysis and Mann-Kendall statistical test, we analyze the characteristics of the direct and diffusion radiation from different aspects including decadal variation, long-term seasonal change, inter-decadal anomaly, cycle and abrupt change. The results are as follows. 1) The spatial and temporal distribution of the climatic trend for the direct and diffuse radiation are revealed by using the normalized climatic tendency coefficient. At the same time, these results are comparable. 2) The direct solar and diffuse radiation in China show decreasing trend, but there are many differences in region, inter-annual and seasonal trend. 3) Based on the characteristics of the geographical distribution on observation stations and according to the climate zone, the classification and the statistical analysis of the percentage of site occupation the long-term changes of the radiation can be clearly shown to have the characteristics of area and local difference. 4) Using wavelet and Mann-Kendall test method, the statistical results show that the radiations in different regions have different periods and abrupt change. 5)The long-term variations of the direct and diffuse radiation in most big cities turn to decrease more obviously than in other cities. Some. Other studies show that such a climatic phenomenon may be caused by environmental factor change of urbanization related to the difference in development speed between cities.

A Revisit of Direct and Diffuse Solar Radiation in China Based on Homogeneous Surface Observations: Climatology, Trends, and Their Probable Causes

“…Significant ( p < 0.01) correlations with R d are shown for elevation (0.86) and TCC (−0.61); R d values lower than 70 W m −2 and higher than 90 W m −2 are largely concentrated in the regions of south China with TCC values over 60% and west China with elevations over 2,000 m, respectively. The spatial distribution of R d generated over 11 homogeneous stations across China is consistent with that proposed by previous studies (Ma et al, ; Zhao et al, ; Zuo & Gong, ).…”

“…During the global dimming phase of 1961-1989, the decreases of R d cover all the examined stations, with 73% of the decreasing trends being significant (Figure 5a). Significant dimming trends of R d are largely concentrated in the eastern part of China, that is, the regions of south and north China (Figure 1), with low R d energy reserves (Figure 2a), consistent with previous analyses on the spatial patterns of R d trends during the global dimming phase (Liang & Xia, 2005;Ma et al, 2011;Shi et al, 2008;Zhao et al, 2009). Opposite spatial patterns are shown for R f % with overall increases covering 91% of the stations (Figure 5g), which are especially significant over the eastern part of China with higher proportion of R f (Figure 2c).…”

“…The low R f values generally distribute in the areas with high latitude, dry climate, or low TCC, and vice versa. Similar spatial patterns of R f were derived for China by Ma et al () and Ren et al () based on surface‐observed and SD‐estimated spatial data of R f , respectively. Despite the good representativeness of the 11 homogenous stations for China, to generate a full picture of the climatology of R d and R f in China, high‐quality R d and R f data with better spatial representation are highly in need.…”

“…The individual and overall variations of SO 2 emissions and R f % were then compared over the 11 homogenous stations to investigate possible implications of emission control efforts for the R f % variations in China. (Ma et al, 2011;Zhao et al, 2009;Zuo & Gong, 1962).…”

“…The global dimming and brightening phenomena are functions of the changes in the sum of the direct (R d ) and diffuse (R f ) radiation components, which are respectively the fractions of R from the direction of the Sun and from the different directions in the rest of the sky dome scattered by clouds, aerosols, gases, and water droplets in the atmosphere (Calbó et al, 2017;Kvalevåg & Myhre, 2007;Ma et al, 2011). R d , which is an environment-friendly energy source and one of the most abundant renewable energy resources for Earth, is essential for the generation of solar power (Feng et al, 2017;Kambezidis, 2018).…”