Abstract: Based on the 1960-2007 daily precipitation data from 13 meteorological stations in Changbai Mountains, and by using the concepts of precipitation concentration degree and precipitation concentration period, an analysis on the precipitation characteristics in this region in growth season was carried out, with the proposing of the index precipitation concentration point. In the study region, the average precipitation concentration degree in past years was 0.31, and its interannual and interdecadal variations were obvious. The precipitation concentration degree of 10-year quasi-period fluctuated markedly. There was an obvious spatial non-uniformity of precipitation concentration degree among the 13 meteorological stations. The average precipitation concentration period in past years was 84.6 d, also with obvious interannual and interdecadal variations. The average variance was 9.7 d, and the variation coefficient was 11.5%. An obvious spatial non-uniformity was also observed in the precipitation concentration period among the 13 meteorological stations, and the average variance was 10.9 d.

Key words: Chlorine dioxide, Algaecide, Phaeocystis globosa, Red tide