Kosa (Aeolian dust) is a kind of aerosol blown up from semi-arid areas of the Asian continent and transported by westerly winds to Japan. A total of 11 JMA meteorological stations (as of 31 December 2023) perform Kosa monitoring. The phenomenon is recorded when visually observed by station staff.
The number of days when any meteorological station in Japan observed Kosa was 14 in 2023, and the total number of stations reporting its occurrence during the year was 40.
Both the number of days on which Kosa was observed and the annual total number of stations reporting observation show large interannual variability but no discernible trend between 1967 and 2023.
Number of days when any station in Japan observed Kosa (1967-2023)
Based on the 11 stations that were active for the whole period.
Annual total number of stations observing Kosa in Japan (1967-2023)
Based on the 11 stations that were active for the whole period.
Average monthly number of days when any station in Japan observed Kosa (1991-2020)
Based on the 11 stations that were active for the whole period.