Yoshihiro IGARI

Improved Method for Estimating Surface Precipitation by Backward Trajectory Line Analysis Considering The Fall Speed of Each Solid Precipitation Particle Type

Toshiro KUMAKURA

In Niigata Prefecture and other regions with heavy snowfall, winter snowfall can be a snow and ice hazard that affects people's lives. In order to control the damage caused by snow and ice disasters, it is necessary to understand the amount and type of precipitation on the ground.However, because precipitation particles are affected by wind-driven advection, the results of weather radar observations over the sky and ground observations do not match, but can be avoided by estimating precipitation on the ground surface using backword trajectory. However, it is known that the fall speed of precipitation particles differs greatly by type in the case of solid precipitation. In this study, we investigated whether it is important to evaluate the difference in fall speeds related to particle type in order to perform backword trajectory.We compared the results of backward trajectory analysis when the main fall velocity was selected based on the volume and number of particles, and when the representative velocity was 1.1 m/s for snowflakes, using the distribution of fall speeds of solid precipitation observed on the ground every minute. The results of precipitation on the radar observation surface and precipitation particle discrimination by KOUKETSU et al. were applied to the MP radar installed in Nagaoka City and compared with the ground-based observations, respectively.For the comparison, we used a case where hail and snowflakes were continuously observed on the ground. The results showed that the observation fall velocity setting improved the accuracy by 17.7% for the hail case and by 27.3% for the snowflake case compared to the 1.1 m/s setting. In the case of hail, in particular, the accuracy was 85.3% when the observed fall rate was given, confirming that the type of precipitation could be determined with a high degree of accuracy. In addition, the comparison of precipitation amounts showed that the setting of the observed fall velocity improved the accuracy of estimation of precipitation amounts and temporal trends for both hail and snowflakes compared to the case of 1.1 m/s. This confirms that there are cases that are important for backword trajectory.