Author(s): Yoshiya Touge, Grace Puyang Emang, So Kazama
Keywords: Forest fire; Dryness hazard; Land surface model; Soil moisture; Tohoku;
Abstract: In the spring of 2017, several forest fires widely occurred simultaneously in the Tohoku region. In the largest event occured in Kamaishi city, Iwate Prefecture, 413ha area was burned which exceeds total burnt area in whole Japan in 2016. Forest fires are one of dryness hazard and wind hazard, and these natural conditions increases occurences and explands larger. Since the 2017 events were extreme event in bunrt area in Japan, natural condition would affect them. Therefore, analyzing the natural conditions at that time will lead to understand affection of natural condition to forest fires, to predict for warning, and to project climate change impact. Main natural conditions affecting forest fires are soil moisture, atmospheric humidity and wind speed. Since precipitation in 2017 winter was only 70% from long-term average, the lower rainfall integrated over a long period and the soil would be dry at that time.
Therefore, in this research, we focused on soil mositure at surface layer and analyzed it using land surface model. As a result, it was found that analyzed surface soil mositure was low in the spring season of 2015 and 2017, which had many forest fires in Tohoku region and was considered to be a dry year. And since the drying process started from autumn to spring, precipitation at that time is important for soil moisture dryness in the spring. However in 2012, precipitation was low in the winter, but soil moisture dryness was not high in spring due to strong rainfall in March. Occurrence of forest fire was also not high comparing to other years. Therefore, it was shown that not only total amount of precipitation but also the timing of precipitation are important. Soil moisture analysis by land surface model could consider these drying process, so it could be an indicator for dry condition of the soil.