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SUMMARY:A study of aerosol impacts on clouds and precipitation development
  in a large winter cyclone - Greg Thompson (NCAR)
DTSTART:20150518T100000Z
DTEND:20150518T110000Z
UID:TALK59013@talks.cam.ac.uk
CONTACT:Dr Amanda Maycock
DESCRIPTION:Aerosols influence cloud and precipitation development in comp
 lex ways due to myriad feedbacks at a variety of scales from individual cl
 ouds through entire storm systems. This paper describes the implementation
 \, testing\, and results of a newly modified bulk microphysical parameteri
 zation with explicit cloud droplet nucleation and ice activation by aeroso
 ls. Idealized tests and a high-resolution\, convection-permitting\, contin
 ental-scale\, 72-h simulation with five sensitivity experiments showed tha
 t increased aerosol number concentration results in more numerous cloud dr
 oplets of overall smaller size and delays precipitation development. Furth
 ermore\, the smaller droplet sizes cause the expected increased cloud albe
 do effect and more subtle longwave radiation effects. Although increased a
 erosols generally hindered the warm-rain processes\, regions of mixed-phas
 e clouds were impacted in slightly unexpected ways with more precipitation
  falling north of a synoptic-scale warm front. Aerosol impacts to regions 
 of light precipitation\, less than approximately 2.5 mm/h\, were far great
 er than impacts to regions with higher precipitation rates. Comparisons of
  model forecasts with five different aerosol states versus surface precipi
 tation measurements revealed that even a large-scale storm system with nea
 rly a thousand observing locations did not indicate which experiment produ
 ced a more correct final forecast\, indicating a need for far longer-durat
 ion simulations due to the magnitude of both model forecast error and obse
 rvational uncertainty. Last\, since aerosols affect cloud and precipitatio
 n phase and amount\, there are resulting implications to a variety of end-
 user applications such as surface sensible weather and aircraft icing.
LOCATION:Todd Hamied\, Department of Chemistry
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