Reduction in Sunshine Duration and Related Factors over Mainland China during 1961–2016

Abstract

As a kind of renewable energy, the development and utilization of solar energy is valued by many countries. Sunshine duration (SD), as an important factor to measure solar energy, has also been widely discussed as relevant in terms of distribution and variation. The spatial patterns and variation trends in SD and related factors (wind speed, precipitation, relative humidity, mean temperature and elevation) over mainland China have been studied based on data from 569 meteorological stations during 1961-2016. The results indicated that annual SD decreased significantly at the rate of −40.7 h/10a over mainland China and the decline trend was the most pronounced in the 1980s. Seasonally, the decline rate in SD was the largest in summer (−16.8 h/10a), followed by winter (−9.9 h/10a), autumn (−9.5 h/10a) and spring (−4.5 h/10a), respectively. Spatially, the decline trend in SD was significantly higher in the eastern region than in the western region during 1961-2016, especially in North China. SD was positively correlated with wind speed (R = 0.76); however, it was negatively correlated with mean temperature (R = −0.60) and precipitation (R = −0.41). Moreover, altitude and population density may affect the values and variations of annual SD over mainland China. This study provides a new perspective for the reduction of SD in mainland of China. The drastic changes in SD, such as abrupt changes and sudden decreases, were closely related to volcanic eruptions. Among them, the mean mutation and sudden decrease of SD in the 1980s were due to the long-time weakening of the aerosol accumulated by multiple volcanic eruptions. After the volcanic eruptions in the early 1990s, volcanic aerosols were gradually dissipating, resulting in a small rebound in SD.

A new view on the trend of solar radiation in mainland China - Based on the optimized empirical model

“…The trend of SR changes in the late 1980s, from decreasing to increasing, consistent with the findings of Wang et al (Wang et al, 2013). However, after a rapid decline in SD in the 1980s, the trend gradually stabilizes, as is also reported by Song et al (Song et al, 2019) and Feng et al (Feng et al, 2019). Six empirical models are verified with the measured data of 31 radiation sites as true values, among which the cubic model shows the best consistency.…”

A new view on the trend of solar radiation in mainland China — based on the optimized empirical model

“…The trend of SR changes in the late 1980s, from decreasing to increasing, consistent with the findings of Wang et al (Wang et al, 2013). However, after a rapid decline in SD in the 1980s, the trend gradually stabilizes, as is also reported by Song et al (Song et al, 2019) and Feng et al (Feng et al, 2019). Six empirical models are verified with the measured data of 31 radiation sites as true values, among which the cubic model shows the best consistency.…”

“…(2) Although the theory proposed in this study can explain the difference between SD and SR changes well, the sudden rise in SR around 1992 is still puzzling. Based on previous studies (Feng et al, 2019), we cautiously conjecture that this sudden change may be related to the dissipation of volcanic aerosols accumulated in the atmosphere from the 1980s to the early 1990s.…”

Association of sleep behavior with depression: a cross-sectional study in northwestern China

“…This suggests that participants in northwest China might have shorter sleep duration and more sleep problems. This might be due to a variety of factors, including variation in diet habit, economy level, urbanization level, rhythm of life, and day length (13,30,31).…”