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The influence of aerosol concentrations on the glaciation and precipitation of a cumulus cloud

Phillips, Vaughan LU ; Choularton, TW; Blyth, AM and Latham, J (2002) In Quarterly Journal of the Royal Meteorological Society 128(581). p.951-971
Abstract
The response of the glaciation and precipitation of U multi-thermal cumulus cloud to changes in the aerosol concentration has been assessed in a series of sensitivity tests with the UMIST Explicit Microphysics Model (EMM). A simulation of this cloud from the Met Office cloud-resolving model (CRM) has been utilized in these tests. This cumulus cloud was observed h aircraft during the initial stage of its growth over New Mexico on 10 August 1987. The growth of the simulated cloud is divided into two parts: a shallow phase followed by a deep phase. Maximum values of the cloud depth in these two phases were 5 and 9 km. respectively. In the EMM simulations including only the shallow phase, the precipitation efficiency was found to decrease... (More)
The response of the glaciation and precipitation of U multi-thermal cumulus cloud to changes in the aerosol concentration has been assessed in a series of sensitivity tests with the UMIST Explicit Microphysics Model (EMM). A simulation of this cloud from the Met Office cloud-resolving model (CRM) has been utilized in these tests. This cumulus cloud was observed h aircraft during the initial stage of its growth over New Mexico on 10 August 1987. The growth of the simulated cloud is divided into two parts: a shallow phase followed by a deep phase. Maximum values of the cloud depth in these two phases were 5 and 9 km. respectively. In the EMM simulations including only the shallow phase, the precipitation efficiency was found to decrease substantially with increasing atmospheric concentrations of cloud condensation nuclei (CCN). Also, the graupel mixing ratio and total ice concentration ere found to decrease as normalized CCN concentration are increased above typical continental values. These changes are explicable in terms of: (I) the Hallett-Mossop (H-M) process at -3 to -8 degreesC and the freezing of supercooled raindrops in collisions with ice splinters dominating the glaciation and (2) the warm-rain process being more significant for the overall precipitation production than the ice process in these particular Simulations. The almost complete suppression of precipitation by extreme CCN concentrations corresponding to a forest-fire plume in the EMM simulation is consistent with the analysis by Rosenfeld of satellite images of Indonesian cumuli engulfed by smoke from biomass burning. A clear tendency for ice crystals to be smaller and more numerous in the anvil as found with increasing CCN concentrations beyond typical continental values in long-term simulations that included the deep phase. The sensitivity of the precipitation rate to the normalized CCN concentration was found to be relatively low in these deep cases. (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
keywords
cloud-condensation nuclei, cloud-resolving model, Hallett-Mossop, process, riming
in
Quarterly Journal of the Royal Meteorological Society
volume
128
issue
581
pages
951 - 971
publisher
Royal Meteorological Society
external identifiers
  • wos:000175327800010
  • scopus:0036541855
ISSN
0035-9009
DOI
10.1256/0035900021643601
language
English
LU publication?
no
id
6554648c-1e07-4616-9216-60a02aec3838 (old id 4587611)
date added to LUP
2014-08-15 10:03:45
date last changed
2017-11-19 03:40:42
@article{6554648c-1e07-4616-9216-60a02aec3838,
  abstract     = {The response of the glaciation and precipitation of U multi-thermal cumulus cloud to changes in the aerosol concentration has been assessed in a series of sensitivity tests with the UMIST Explicit Microphysics Model (EMM). A simulation of this cloud from the Met Office cloud-resolving model (CRM) has been utilized in these tests. This cumulus cloud was observed h aircraft during the initial stage of its growth over New Mexico on 10 August 1987. The growth of the simulated cloud is divided into two parts: a shallow phase followed by a deep phase. Maximum values of the cloud depth in these two phases were 5 and 9 km. respectively. In the EMM simulations including only the shallow phase, the precipitation efficiency was found to decrease substantially with increasing atmospheric concentrations of cloud condensation nuclei (CCN). Also, the graupel mixing ratio and total ice concentration ere found to decrease as normalized CCN concentration are increased above typical continental values. These changes are explicable in terms of: (I) the Hallett-Mossop (H-M) process at -3 to -8 degreesC and the freezing of supercooled raindrops in collisions with ice splinters dominating the glaciation and (2) the warm-rain process being more significant for the overall precipitation production than the ice process in these particular Simulations. The almost complete suppression of precipitation by extreme CCN concentrations corresponding to a forest-fire plume in the EMM simulation is consistent with the analysis by Rosenfeld of satellite images of Indonesian cumuli engulfed by smoke from biomass burning. A clear tendency for ice crystals to be smaller and more numerous in the anvil as found with increasing CCN concentrations beyond typical continental values in long-term simulations that included the deep phase. The sensitivity of the precipitation rate to the normalized CCN concentration was found to be relatively low in these deep cases.},
  author       = {Phillips, Vaughan and Choularton, TW and Blyth, AM and Latham, J},
  issn         = {0035-9009},
  keyword      = {cloud-condensation nuclei,cloud-resolving model,Hallett-Mossop,process,riming},
  language     = {eng},
  number       = {581},
  pages        = {951--971},
  publisher    = {Royal Meteorological Society},
  series       = {Quarterly Journal of the Royal Meteorological Society},
  title        = {The influence of aerosol concentrations on the glaciation and precipitation of a cumulus cloud},
  url          = {http://dx.doi.org/10.1256/0035900021643601},
  volume       = {128},
  year         = {2002},
}