Insights into riming and aggregation processes as revealed by aircraft, radar, and disdrometer observations for a 27 April 2011 widespread precipitation event: Insights into Riming and Aggregation

Journal Article · Thu May 19 04:00:00 UTC 2016 · Journal of Geophysical Research: Atmospheres

DOI: https://doi.org/10.1002/2015JD024537 · OSTI ID:1260164

Giangrande, Scott E. ^[1]; Toto, Tami ^[1]; Bansemer, Aaron ^[2]; Kumjian, Matthew R. ^[3]; Mishra, Subhashree ^[4]; Ryzhkov, Alexander V. ^[4]

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1. Atmospheric Sciences Division, Brookhaven National Laboratory, Upton New York USA
2. National Center for Atmospheric Research, Boulder Colorado USA
3. Department of Meteorology, Pennsylvania State University, University Park Pennsylvania USA
4. Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma and NOAA/National Severe Storms Laboratory, Norman Oklahoma USA

Our study presents aircraft spiral ascent and descent observations intercepting a transition to riming processes during widespread stratiform precipitation. The sequence is documented using collocated scanning and profiling radar, including longer-wavelength dual polarization measurements and shorter-wavelength Doppler spectra. Riming regions are supported using aircraft measurements recording elevated liquid water concentrations, spherical particle shapes, and saturation with respect to water. Profiling cloud radar observations indicate riming regions during the event as having increasing particle fall speeds, rapid time-height changes, and bimodalities in Doppler spectra. These particular riming signatures are coupled to scanning dual polarization radar observations of higher differential reflectivity (ZDR) aloft. Moreover, reduced melting layer enhancements and delayed radar bright-band signatures in the column are also observed during riming periods, most notably with the profiling radar observations. The bimodal cloud radar Doppler spectra captured near riming zones indicate two time-height spectral ice peaks, one rimed particle peak, and one peak associated with pristine ice needle generation and/or growth between -4°C and -7°C also sampled by aircraft probes. We observe this pristine needle population near the rimed particle region which gives a partial explanation for the enhanced ZDR. The riming signatures aloft and radar measurements within the melting level are weakly lag correlated (r~0.6) with smaller median drop sizes at the surface, as compared with later times when aggregation of larger particle sizes was believed dominant.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
• OSTI ID: 1260164
• Report Number(s): BNL--112320-2016-JA; KP1701000
• Journal Information: Journal of Geophysical Research: Atmospheres, Journal Name: Journal of Geophysical Research: Atmospheres Journal Issue: 10 Vol. 121; ISSN 2169-897X
• Publisher: American Geophysical UnionCopyright Statement
• Country of Publication: United States
• Language: English