Abstract: Using on-the-ground meteorological measurements and NCEP/NCAR reanalysis data from 1989 to 2020, we examined changes in wind speed and direction at Zhongshan Station in Antarctica and the mechanisms underlying observed changes. Our findings are as follows: (1) There are clear seasonal variations in wind speed at Zhongshan Station. The wind speed is the highest in winter, second highest in autumn, and the lowest in summer. During the day, wind speed reaches its maximum value at 5 am local time, and its minimum value at 3 pm; there is a single maximum and a single minimum per day. Diurnal variations are large in spring and summer, but small in autumn and winter. (2) Wind speed and frequency of katabatic wind and gale days at Zhongshan Station have decreased over the past 31 years. The rate of decrease is the highest in summer. Results from wind vector decomposition show that the rate of decrease of the southerly winds is significantly higher than the rates of decrease of winds in other directions. The trends of the westerly and northerly winds are not significant. The negative trend of the easterly winds is only significant in summer. (3) The decrease of annual mean wind speed at Zhongshan Station is mainly caused by the decrease in moderate gale and gale days. The changes observed at Zhongshan Station are related to changes in the atmospheric circulation. The weakening of the cold polar high to the south of Zhongshan Station and of the extreme low in the north of the southern Indian Ocean result in a decrease in the pressure gradient and reduced wind speeds at Zhongshan Station.

Key words: Antarctica, Zhongshan Station, wind speed, variation in long-term