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The impact of atmospheric aerosols on precipitation from deep organized convection: A prescribed‐flow model study using double‐moment bulk microphysics
Author(s) -
Slawinska Joanna,
Grabowski Wojciech W.,
Morrison Hugh
Publication year - 2009
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.450
Subject(s) - squall line , precipitation , convection , environmental science , cloud physics , depth sounding , atmospheric sciences , meteorology , cloud condensation nuclei , precipitation types , convective available potential energy , inflow , flow (mathematics) , geology , mechanics , physics , aerosol , cloud computing , oceanography , computer science , operating system
Abstract This note discusses the results of numerical simulations in which a prescribed‐flow model is merged with a double‐moment warm‐rain and ice microphysics scheme to investigate the impact of microphysical processes on precipitation from deep organized convection. The prescribed two‐dimensional flow mimics an idealized squall line, with a narrow region of strong convective updraft and much wider region of weak stratiform updraft overlaying a stratiform downdraft. To cover the broad range of conditions that are possible for a squall line as well as to explore precipitation dependence on different parameters, 25 pairs of simulations are performed. Simulated cases differ in the dynamics (e.g. changing the updraft strength or large‐scale shear), thermodynamics (e.g. changing the inflow sounding) or microphysics (e.g. changing the collision efficiencies). Each pair features cloud condensation nuclei (CCN) in either a pristine or polluted environment. Total surface precipitation and partitioning between convective and stratiform precipitation in each pair appears to be almost the same, with the difference being typically a few tenths of 1%. However, the dynamical and thermodynamical parameters do affect the precipitation significantly. It follows that the surface precipitation from organized convection can differ between pristine and polluted environments only through the feedback of CCN on cloud dynamics. In this feedback, small differences in the latent heating for the same flow pattern lead to different flow patterns in subsequent squall‐line evolution. Details of this feedback need to be investigated using a dynamical model. Copyright © 2009 Royal Meteorological Society