Recent Trend of Forest Fires in Sakha and Large-Scale Fires in 2002

Abstract

Recent trend of the forest fires and climate in Sakha, Siberia was showed by analyzing the fire history and climate data. The following conclusions were obtained. (1) Analysis of forest fire history from the mid 1950 s in Sakha showed that the mean annual number of forest fires and burnt area were at about 500 and 2,700 km² respectively. The average burnt area has been increasing since the 1990 s. (2) Analysis of the climate in Yakutsk, Sakha from the nineteenth century showed that the mean air temperature rise since 1830 was about 3 °C. The recent remarkable temperature rise began from the 1970 s. (3) The precipitation history from 1890 showed a gradual decrease beginning from the 1970 s. Specially, the daily mean precipitation in fire season(from May to September)was drastically decreased from the 1990 s. These decreases in precipitation may make boreal forests more dry or flammable. Actually, in 2002, large-scale forest fires occurred near Yakustk under these ongoing global warming condition. (4) A detailed analysis of recent precipitation patterns in Yakutsk, Sakha implies that forest fires became large when annual precipitation is smaller than a mean precipitation or 250 mm. (5) Precipitation patterns also had a great effect to forest fires. A considerable amount of rain in June is a key element in controlling fires in Yakutsk. Actually, about 50 mm of precipitation in June of 1995 seemed to suppress forest fires to a level below the fire year. The total precipitation in 1995 was 185 mm .(6) Thus, catastrophic fires in 2002 occurred due to the above-mentioned low precipitation conditions. Lightning may ignite fires in July because several fires occurred at almost the same time and at some distance from populated areas.