Vertical distribution of precipitation particles in Baiu frontal stratiform intense rainfall around Okinawa Island, Japan

• Published in: Journal of geophysical research. Atmospheres 2015-06, Vol.120 (11), p.5622-5637
• Main Authors: Oue, M., Ohigashi, T., Tsuboki, K., Nakakita, E.
• Format: Article
• Language: English
• Subjects: Atmospheric precipitations; Atoms & subatomic particles; Baiu; Cells; Clouds; Convection; Convective cells; Convective precipitation; Crystals; Diameters; Dimensions; DSD; Geophysics; Hydrometeors; Ice environments; ice particles; Islands; Marine; Meteorology; Particle size distribution; Polarimetric radar; Precipitation; Precipitation processes; Radar; Radar data; Radar polarimetry; Radar reflectivity; Rain; Raindrop size distribution; Raindrops; Rainfall; Reflectance; Sea level; Size distribution; Stratiform clouds; stratiform rain; Vertical distribution
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1002/2014JD022712

The vertical distribution of precipitation particles in an intensely precipitating stratiform cloud associated with the Baiu front around Okinawa Island was observed. X‐band polarimetric radar, disdrometer, and hydrometeor videosonde data were used to examine the precipitation processes. The cloud top was approximately 12 km above sea level, as convection was depressed while stratiform regions developed near Okinawa Island. In the rain region below 3 km, the mean median volume diameter of the raindrop size distribution (DSD) estimated from the radar variables was 1.55 mm, and the mean normalized intercept parameter was 104.12 mm−1 m−3 with a mean radar reflectivity of 40.5 dBZe. The DSD indicates that the stratiform precipitation was characterized by higher number concentrations of smaller drops than observed previously in convective cells in a Baiu frontal convective precipitation region around Okinawa Island. The DSD also suggests the presence of larger raindrops than in convective cells embedded in a Baiu frontal stratiform precipitation region around Okinawa Island. In the ice region at 5–6 km, just above the melting layer and 6 km below the cloud top, the differential reflectivity and specific differential phase showed positive values, and videosonde measurements revealed that the number concentration of column‐, plate‐, and capped‐column‐like crystals (maximum dimensions of ≥0.1 mm) was 112 L−1. The high number concentration of these crystals contributed to the intense stratiform rainfall associated with the Baiu front. Key Points Contribution of high ice crystal concentration to Baiu intense stratiform rain Higher number density smaller raindrops than in Baiu convective cells Presence of larger raindrops than in Baiu embedded convective cells