The characteristics of daily solar irradiance variability and its relation to ozone in Hefei, China

The MS-711 spectroradiometer was used to measure the 300–1100 nm solar spectral irradiance in four typical months in Hefei, to study the local solar radiation characteristics, and analyze the correlation with the ground ozone concentration. The results show that the monthly average irradiance in Hefei is July, April, October, and January in order from high to low, and the frequency of the monthly average maximum irradiance is about 470 nm. The visible light band radiant energy accounts for more than 61%, followed by the infrared band, which accounts for more than 30%. In July, the proportion of visible light and ultraviolet radiation energy increased. The response of ground-level ozone concentration to solar radiation is significant, and the delay response time is about 3 h, which is verified by the largest correlation coefficient calculated from solar radiation and the ozone concentration after 3 h. The delayed response of ozone to irradiance becomes stable and almost no frequency difference when the spectral frequency is greater than 325 nm, but the response time is different in different seasons; it is the shortest in summer and becomes longer in winter, autumn, and spring. The weather also affects this correlation. The correlation is weakest on cloudless days in summer, and it is stronger on cloudy, rainy days, and cloudless days in winter. This phenomenon suggests that there may be a subtle relationship between solar radiation, precursors, and atmospheric diffusion capabilities, and that solar radiation drives photochemical reactions and dominates changes in ground-level ozone only when they vary within a certain range.