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UID:20260810T122511EDT-3026p21Zug@132.216.98.100
DTSTAMP:20260810T162511Z
DESCRIPTION:Please join us as we welcome Dr. Allison Wing from the Lamont D
 oherty Earth Observatory at Columbia University for her seminar titled Org
 anization of tropical convection: Self-aggregation and spontaneous tropica
 l cyclogenesis. Refreshments will be served.\n\nAbstract\n\nTropical cloud
 s and relative humidity play a key role in both the planetary energy balan
 ce and the sensitivity of global climate to radiative forcing. Both clouds
  and relative humidity are also strongly modulated by the organization of 
 tropical convection\, which results in a large fraction of tropical cloudi
 ness and rainfall. Here\, we investigate the organization of tropical conv
 ection in the context of self-aggregation\, a spontaneous transition in id
 ealized numerical  simulations from randomly distributed to organized conv
 ection despite homogeneous boundary conditions. Specifically\, the System 
 for Atmospheric Modeling is used to perform 3-d simulations of radiative-c
 onvective equilibrium in a non-rotating framework\, with interactive radia
 tion and surface fluxes and fixed sea surface temperatures. The results of
  simulations employing a highly elongated 3-d channel domain\, in which se
 lf-aggregation takes the form of multiple moist and dry bands\, are compar
 ed to that of a square domain\, in which self-aggregation takes the form o
 f a single moist cluster. For both domain types\, and across a range of te
 mperatures\, we characterize the fundamental physical mechanisms that lead
  to self-aggregation as well as its growth rate and spatial scale. In both
  geometries\, cloud-radiative feedbacks and surface flux feedbacks are fou
 nd to be important in the initial instability\, but advection only contrib
 utes to aggregation in the square geometry.\n\nSelf-aggregation has primar
 ily been studied in a non-rotating framework\, but it has been hypothesize
 d to be important to tropical cyclogenesis. In numerical simulations of tr
 opical cyclones\, a broad vortex or moist bubble is often used to initiali
 ze the circulation. Here\, we instead allow a circulation to develop spont
 aneously from a homogeneous environment in 3-d cloud-resolving simulations
  of radiative-convective equilibrium (RCE) in a rotating framework\, and c
 ompare the resulting tropical cyclogenesis to non-rotating self-aggregatio
 n. We find that in the initial development of a broad circulation\, the fe
 edback processes leading to cyclogenesis are similar to the initial phase 
 of non-rotating aggregation. Sensitivity tests in which the degree of inte
 ractive radiation is modified are also performed to determine the extent t
 o which the radiative feedbacks that are essential to non-rotating self-ag
 gregation are important for tropical cyclogenesis.\n
DTSTART:20160118T203000Z
DTEND:20160118T213000Z
LOCATION:Room 934\, Burnside Hall\, CA\, QC\, Montreal\, H3A 0B9\, 805 rue 
 Sherbrooke Ouest
SUMMARY:Seminar: Dr. Allison Wing
URL:/channels/event/seminar-dr-allison-wing-257174
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