Tomoki FURUHASHI

Estimation and Validation of Solid Precipitation on the Ground Using Measured Radar Precipitation and 3D Wind Field Data

Toshiro KUMAKURA

Nowadays, it is common practice to use the vertical projection of radar precipitation observed in the sky onto the ground surface for reporting precipitation on the ground. However, solid precipitation, such as snowflakes, is strongly affected by winds in the sky due to its shape and mass, and is thus swept far away from the ground. In this study, we performed a backward trajectory analysis by linear interpolation of horizontal wind speed, altitude and time data from ground observation points using east-west and north-south wind speed data from a numerical forecast model, and constructed an environment that can analyze radar precipitation at the coordinates of the intersection of the backward trajectory and the radar beam from a multi-parameter radar installed on the environmental building at the Nagaoka University of Technology as estimated solid precipitation that reaches the ground while receiving wind advection above the ground.Using this method, we assumed that snowflakes were observed during the period from February 5 to 14, 2020, when the surface temperature was below 2 degC and the falling snow depth was above 1 cm/h. Calcurating the backward trajectory at six AMeDAS stations in Niigata Prefecture (Nagaoka, Kashiwazaki, Sumon, Koide, Tokamachi, and Tsugawa), In addition, estimated precipitation, radar precipitation directly above AMeDAS, and AMeDAS precipitation were compared.As a result, it was found that, in the case of February 5-6, 2020, when the wind was strong throughout the prefecture due to a mountain-snow type pressure pattern, cloud areas with a certain amount of precipitation were sparsely scattered within the analysis area, the backward trajectory line sometimes referred to precipitation in another cloud area than the snow cloud actually observed directly above the AMeDAS station.