Abstract:

This study analyzed the climate change characteristics and causes of foggy days in Qingdao and Jinan using meteorological observation data from 1961 to 2020 in Qingdao and Jinan, as well as sea surface temperature data near Qingdao. Results showed that the average annual foggy days in Qingdao were 50.4 d, 3.1 times more than that in Jinan. The peak fog seasons were substantially different in the two cities; Qingdao experiences more foggy days in spring and summer, accounting for about 78.4% of the whole year, whereas Jinan experiences more foggy days in autumn and winter, accounting for about 70.7% of the whole year. Furthermore, remarkable differences in the annual and seasonal variations of foggy days were observed. Qingdao shows an increasing trend in annual foggy days, i.e., less foggy days in spring and summer, but significantly more in autumn and winter. Alternatively, Jinan exhibits a decreasing trend in annual foggy days, where the number of foggy days is lowest in autumn. Moreover, considerable climate variability and abrupt change in the number of annual foggy days between the two cities were noticed. The climate variability of Qingdao showed an increasing trend and remained at a high level, while Jinan witnessed a decreasing trend; this indicates a higher probability of extreme foggy weather in Qingdao than in Jinan. Qingdao witnessed an increase in the number of foggy days in 1969, while Jinan encountered a decrease in 1995. The increase in the number of foggy days in Qingdao during autumn and winter was closely related to the substantial increase in the sea surface temperature near the city. This increase promoted sea surface evaporation and subsequently increased the atmospheric water vapor content. However, the decrease in foggy days in Jinan during autumn and winter was closely associated with a substantial increase in the minimum temperature and the dew point temperature difference as well as reduced humidity.

Key words: Qingdao, Jinan, foggy days, climate change, difference analysis