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contributor authorMuller, Caroline J.
contributor authorHeld, Isaac M.
date accessioned2017-06-09T16:54:36Z
date available2017-06-09T16:54:36Z
date copyright2012/08/01
date issued2012
identifier issn0022-4928
identifier otherams-76366.pdf
identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4218805
description abstractn models of radiative?convective equilibrium it is known that convection can spontaneously aggregate into one single localized moist region if the domain is large enough. The large changes in the mean climate state and radiative fluxes accompanying this self-aggregation raise questions as to what simulations at lower resolutions with parameterized convection, in similar homogeneous geometries, should be expected to produce to be considered successful in mimicking a cloud-resolving model.The authors investigate this self-aggregation in a nonrotating, three-dimensional cloud-resolving model on a square domain without large-scale forcing. It is found that self-aggregation is sensitive not only to the domain size, but also to the horizontal resolution. With horizontally homogeneous initial conditions, convective aggregation only occurs on domains larger than about 200km and with resolutions coarser than about 2km in the model examined. The system exhibits hysteresis, so that with aggregated initial conditions, convection remains aggregated even at our finest resolution, 500m, as long as the domain is greater than 200?300km.The sensitivity of self-aggregation to resolution and domain size in this model is due to the sensitivity of the distribution of low clouds to these two parameters. Indeed, the mechanism responsible for the aggregation of convection is the dynamical response to the longwave radiative cooling from low clouds. Strong longwave cooling near cloud top in dry regions forces downward motion, which by continuity generates inflow near cloud top and near-surface outflow from dry regions. This circulation results in the net export of moist static energy from regions with low moist static energy, yielding a positive feedback.
publisherAmerican Meteorological Society
titleDetailed Investigation of the Self-Aggregation of Convection in Cloud-Resolving Simulations
typeJournal Paper
journal volume69
journal issue8
journal titleJournal of the Atmospheric Sciences
identifier doi10.1175/JAS-D-11-0257.1
journal fristpage2551
journal lastpage2565
treeJournal of the Atmospheric Sciences:;2012:;Volume( 069 ):;issue: 008
contenttypeFulltext


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