Long-Term Variability of Solar Radiation over an Oasis on the Southern Margin of the Taklimakan Desert, 1961–2023
This study quantitatively analyzes the temporal variability of global solar radiation and its attenuation under different sky conditions in Hotan City, an oasis on the southern margin of the Taklimakan Desert, using monthly and hourly global radiation, temperature, cloud cover, precipitation, and weather phenomenon records from the Hotan National Reference Climatological Station for 1961–2023. The results show that Hotan possesses abundant and stable solar energy resources. Annual global solar radiation exhibits a fluctuating upward trend with a climatic tendency rate of +7.03 MJ/m² per decade, driven primarily by sustained warming and a reduction in dust weather. The annual mean global radiation is 5946.57 MJ/m², with an annual amplitude of 2473.28 MJ/m² and a maximum of 7333.62 MJ/m² in 2017. Mann-Kendall tests identify a significant decline from 1961 to 1986 at −364.01 MJ/m² per decade (α = 0.01), followed by a significant increase from 1987 to 2023 at +147.55 MJ/m² per decade (α = 0.05). Seasonal contributions follow summer (33%) > spring (29%) > autumn (23%) > winter (15%). Monthly radiation is unimodal, peaking in June at 697.21 MJ/m² and reaching a minimum in December. Diurnal radiation is low in the morning and evening and high at midday, with the maximum generally occurring at 13:00 local time. Precipitation, overcast, and cloudy days produce the most pronounced attenuation of global solar radiation. These findings confirm that Hotan’s solar resource is highly abundant and stable, supporting large-scale, sustained development.