[A-CG39] 北極域の科学

[ACG39-P16] Estimation of the type of snowfall particles using a disdrometer and direct ground observation

*杉浦 幸之助^1,2、高橋 桂子¹、宮川 拓真³、滝川 雅之³、平沢 尚彦⁴ (1.富山大学、2.アラスカ大学フェアバンクス校国際北極圏研究センター、3.海洋研究開発機構、4.国立極地研究所)

キーワード：降雪、降雨、直接観測

As the first step in a study to understand the absorption process of black carbon (BC) into snowfall particles in high latitudes, we compared the precipitation measured by a disdrometer and a tipping bucket type rain gauge, as well as the precipitation measured by AMeDAS of the Japan Meteorological Agency. The one-hour precipitation data showed better agreement than the 10-minute precipitation data. Next, measurement of fall velocity and particle size of precipitation particles using the disdrometer was conducted. From these observations, the beginning and the end of precipitation events could be verified. When the fall velocity changed from fast to slow within the same precipitation event, variation in the particle size was observed. In relation to this, the state of atmosphere of each precipitation event was examined using the AMeDAS data (surface temperature and surface relative humidity). Moreover, when the particle size became gradually larger in correspondence with the decrease of fall velocity, change from rain to snow, where sphericity of precipitation particles decreases and air resistance increases, was discussed. Similarly, when both fall velocity and particle size of snowfall particles gradually became smaller, mixture of simple forms of snowfall with larger sphericity, such as graupel, or of rainfall, were discussed. Furthermore, the type of precipitation particle estimated from the fall velocity and particle size measured by the disdrometer did not differ significantly from the shape of snowfall particles confirmed by direct observation with a digital camera. Finally, in order to elucidate the effect of the forms of snowfall particles on the removal process of BC in the atmosphere, which is the most important purpose of this study, it is necessary to accumulate many examples, such as that of continuous snow cloud, compare the data from the disdrometer and direct photography on the ground, and study their relationships with sampled BC concentration.