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

Scott E. Giangrande, Tami Toto, Aaron Bansemer, Matthew R. Kumjian, Subhashree Mishra, Alexander V. Ryzhkov

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

This 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 saturationwith 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. 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. This pristine needle population gives a partial explanation for the enhanced ZDR we observe near this rimed particle region. The riming signatures aloft and radar measurements within the melting level are weakly lag correlated (r~0.6) with smallermedian drop sizes at the surface, as compared with later times when aggregation of larger particle sizes was believed dominant.

Original languageEnglish (US)
Pages (from-to)5846-5863
Number of pages18
JournalJournal of Geophysical Research
Volume121
Issue number10
DOIs
StatePublished - 2016

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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