Wednesday, 24 May 2000
This presentation will discuss numerical results pertinent to the
problem of large-scale convection organization in the tropics. The
problem spans a wide range of spatial and temporal scales and involves
several physical processes, such as atmosphere-ocean interaction, moist
convection, cloud microphysics, radiative transfer, and equatorial wave
dynamics. Many theories have been proposed in the past to explain the
observed large-scale convection organization (e.g., wave-CISK, WISHE,
water vapor feedback, stochastic convective excitation, etc.). First,
2D (x-z) cloud-resolving simulations will be presented in which a
periodic global-scale horizontal domain is used (20,000 km) and a
horizontally homogeneous SST is assumed. These idealized simulations
are relevant to understanding the interaction between tropical
convection and eastward-propagating Kelvin waves. Indeed, the
spontaneous organization of convection into eastward-propagating
super-cloud-clusters is observed in some of the 2D simulations. Second,
the interaction between equatorially-trapped disturbances and tropical
convection as simulated by a nonhydrostatic global model applying the
cloud-resolving convection parameterization (CRCP, Grabowski and
Smolarkiewicz, 1999, Physica D) will be discussed. The CRCP technique
represents subgrid scales of the global model by imbedding a 2D
cloud-resolving model in each column of the global model. Such an
approach is tailored for distributed memory architectures. The modeling
setup is a constant SST aquaplanet (with the size and rotation as
Earth) in radiative-convective equilibrium. Spontaneous development of
eastward-propagating equatorially-trapped disturbances coupled with
tropical super-cloud-clusters is observed in these simulations. The
presentation will discuss these results in the context the current
theories explaining the coupling between convection and large-scale
dynamics in the tropics.
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