2A.5
Measurement of Vertical Air Velocity and Hydrometeors in Stratiform Precipitation by 47-MHz Wind Profiler Radar and 532-nm Polarization Lidar

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Monday, 16 September 2013: 11:30 AM
Colorado Ballroom (Peak 4, 3rd Floor) (Beaver Run Resort and Conference Center)
Masayuki K. Yamamoto, Kyoto Univ., Uji, Kyoto, Japan; and Y. Shibata, M. Abo, T. Mega, H. Hashiguchi, N. Nishi, H. Okamoto, T. Shimomai, M. D. Yamanaka, M. Yamamoto, M. Timbul, and S. Syafjijon

Simultaneous measurement of vertical air velocity (W), particle fall velocity, and hydrometeor phase was carried out using a 47-MHz wind profiling radar and a 532-nm polarization lidar installed at Sumatra, Indonesia (0.2S, 100.32E, 865 m MSL) in December 2008. The 47-MHz wind profiling radar, referred to as the Equatorial Atmosphere Radar (EAR), measured W and reflectivity-weighted particle fall velocity relative to the air (Vz) simultaneously. The lidar measured linear depolization ratio (LDR), which is an indicator of hydrometeor sphericity.

A stratiform precipitation case on 8 December 2008 and that on 16 December 2008 were compared to describe differences of W, Vz, and LDR. Surface rainfall intensity was greater than 2 mm/h in the 16 December case, while raindrops evaporated until they reached to the ground in the 8 December case. Upward W above the melting level was greater than 0.2 m/s in the 16 December case, while it was weak (less than 0.1 m/s) or absent in the 8 December case. Vz of 1.6 m/s at 300 m above the 0 degC altitude (5.2 km MSL) in the 16 December case was greater than the 8 December case (1.3 m/s). The thickness of melting layer in the 16 December case (900 m) was greater than the 8 December case (300 m). Because Vz is an indicator of particle size, the results suggests that the size growth of hydrometeors under the presence of upward W contributed to the formation of thick melting layer in the 16 December case.

Owing to complex interfaces of water-coated ice crystal branches, LDR at the melting level increased 0.17- 0.20 in the two cases. Lidar dark band was also observed in the two cases. Vz of raindrops in the 16 December case (7.0-7.5 m/s) was greater than that in the 8 December case (3.7-3.9 m/s) due to larger sized raindrops in the 16 December case. LDR of raindrops in the 8 December case was less than 0.01, while it was 0.05-0.10 in the 16 December case. A possible reason for the LDR difference is discussed.