EVALUATE TO VERTICAL GRADIENT OF RADAR REFLECTIVITY ABOVE FREEZING LEVEL ON WINTER PRECIPITATION EVENTS FOCUSING ON SPECIFIC DIFFERENTIAL PHASE

Abstract

 We investigated an index focusing on K_DP (specific differential phase), to evaluate the vertical gradient of Z_H (radar reflectivity) above the freezing level. We proposed an index (AI; Aggregation Index) that express differences in aggregation degree by taking the ratio of K_DP to Z_H. We confirmed that the index AI at an altitude around -9 °C altitude can evaluate the gradient of Z_H above the freezing level when K_DP > 0. We also confirmed that the index AI at -9 °C altitude decreased as the predominant snowfall particles on the ground changed from larger and slightly rimed to smaller and densely rimed in comparison with snowfall particle observations on the ground.