On the mechanisms of rain formation in an idealized supercell storm

Matthew Robert Kumjian, Zachary J. Lebo, Hughbert C. Morrison

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Deep convective storms produce raindrops through three mechanisms: condensation and coalescence growth of cloud liquid droplets (i.e., warm processes), melting of ice hydrometeors, and shedding from wet hailstones. To investigate the relative importance of these mechanisms and their contributions to exotic drop size distributions (DSDs) observed near the surface in supercell storms, an idealized simulation of a supercell is performed using a modified version of the Morrison two-moment microphysics scheme. The modified scheme includes separate categories for warm, shed, and melted rain. Rain originating from melting ice dominates the rain mass at low levels, especially along the right forward-flank precipitation shield, whereas shed-rain drops dominate a region within the left forward flank. Warm rain is only dominant in the upshear portion of the rear flank of the storm at low levels, though it dominates the total rain mass within the main updraft aloft. The warm-rain mass at low levels is associated with strong low-level downdrafts, consistent with previously published hypotheses based on polarimetric radar observations. Raindrops produced via warm processes are smaller on average than those produced by shedding and melting; drops in the latter class tend to be the largest. Overall, the simulations fail to reproduce the diverse nature of observed supercell DSDs, although the modified microphysics scheme does increase the variability of surface DSDs compared to the Control run. This implies that more sophisticated treatment of rain microphysics is needed to capture the natural variability of supercell DSDs, including the ability to evolve the DSD spectral shape through sedimentation and collisional processes.

Original languageEnglish (US)
Pages (from-to)2754-2773
Number of pages20
JournalMonthly Weather Review
Volume143
Issue number7
DOIs
StatePublished - Jan 1 2015

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supercell
melting
raindrop
ice
rain
updraft
coalescence
droplet
simulation
condensation
shield
radar
sedimentation
liquid

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Cite this

Kumjian, Matthew Robert ; Lebo, Zachary J. ; Morrison, Hughbert C. / On the mechanisms of rain formation in an idealized supercell storm. In: Monthly Weather Review. 2015 ; Vol. 143, No. 7. pp. 2754-2773.
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On the mechanisms of rain formation in an idealized supercell storm. / Kumjian, Matthew Robert; Lebo, Zachary J.; Morrison, Hughbert C.

In: Monthly Weather Review, Vol. 143, No. 7, 01.01.2015, p. 2754-2773.

Research output: Contribution to journalArticle

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