First simultaneous measurement of vertical air velocity, particle fall velocity, and hydrometeor sphericity in stratiform precipitation: Results from 47 MHz wind-profiling radar and 532 nm polarization lidar observations

Abstract

Results from simultaneous measurements of vertical air velocity (W), particle fall velocity, and hydrometeor sphericity in stratiform precipitation are reported for the first time. Cases of stratiform precipitation on 8 (case A) and 16 December 2008 (case B) observed at Sumatra, Indonesia (0.2S, 100.32E), are described. A 47 MHz wind-profiling radar measured W and reflectivity- weighted particle fall velocity relative to the air (V Z) simultaneously. Upward W above ∼6.0 km altitude in case B (>0.2 m s -1) was greater than in case A (<0.1 m s -1). V Z at 300 m above the 0C altitude in case B (1.8 m s -1) was greater than in case A (1.3 m s -1). The thickness of melting layer (ML) in case B (900 m) was greater than in case A (300 m). Because the large-sized aggregates contribute to produce greater V Z and thicker ML, it is likely that entangled growth of dendritic crystals under the presence of significant upward W and enhanced aggregation occurrence by the well-developed dendritic crystals produced the large-sized aggregates. Lidar measured an increase of linear depolarization ratio (δ) and lidar dark band in the ML. Volume δ of raindrops was 0.08-0.10 in case B and close to zero in case A. Stronger multiple scattering in case B is likely a cause that produced the greater δ. In case B, a dip of δ was measured at the bottom of ML. The decrease of hydrometeor nonsphericity at the final stage of melting explains the dip. Copyright 2012 by the American Geophysical Union.