Solar dimming and its impact on estimating solar radiation from diurnal temperature range in China, 1961–2007

Abstract

Time series of solar radiation revealed that China experienced an obvious dimming during 1961–1989 and a brightening thereafter. To evaluate the impacts of changing radiation on diurnal temperature range (DTR) and further on estimating solar radiation from DTR, trends in radiation and DTR were analyzed. Among 43 meteorological stations included in the study, 41 sites showed negative trends, and 29 sites were statistically significant during 1961–1989. Minimum temperature (T min) significantly increased, while maximum temperature (T max) slightly decreased during 1961–1989; as a consequence, DTR rapidly decreased (at a rate of −0.033°C year−1) during the same period. Therefore, it is argued that a decline in solar radiation is the primary cause of decreasing DTR through its influence on daytime T max. Since 1990, the decline in DTR had greatly weakened due to reduced difference between the paces of T max and T min as dimming transformed into brightening. Decrease in solar radiation was more obvious than DTR over the dimming period of the 1960s–1980s. The empirical coefficient Kr in the equation R s = Kr(T max − T min)0.5 R a (R s is solar radiation; T max − T min is DTR; R a is extraterrestrial radiation) was a quadratic function of year in the form of Kr = 87 − 0.087 year + 2.2 × 10−5 year2. Kr varied from 0.17 in 1961 to 0.14 in 1999 (around 20%) due to the influence of solar dimming.