Monday, 3 June 2002: 11:15 AM
Cloud microphysics and the tropical climate: Idealized aquaplanet simulations using the cloud-resolving convection parameterization (CRCP)
The essence of tropical dynamics is a mutual interaction between moist
convection and large--scale flow. The interaction involves dynamical,
thermodynamical, radiative and surface processes acting on a wide range
of spatial and temporal scales. It is often argued that the structure of
the tropical atmosphere depends strongly on cloud microphysical
processes because these processes play fundamental roles in the release
of latent heat, formation of precipitation, and interactions between
clouds and radiation. Because of the range of scales involved, this
issue has been previously investigated using approaches with very
simple representations of cloud dynamics and cloud microphysics. This
paper will discuss links between cloud processes and the mean state of
the tropical atmosphere in idealized aquaplanet simulations which apply
the cloud-resolving convection parameterization (CRCP, the
super-parameterization). CRCP represents the subgrid scales of the global
model by embedding a 2D cloud-resolving model in each column of the
global model. The cloud-resolving models are aligned along the
east-west direction and allow for coupling of not only thermodynamic
variables, but the zonal momentum as well. The modeling setup is a
constant SST aquaplanet (with the size and rotation as Earth) in
radiative-convective equilibrium. Spontaneous formation of coherent
structures with deep convection on the leading edge and strong surface
westerly winds to the west (the westerly wind bursts) is observed
inside the equatorial waveguide. These coherent structures resemble the
Madden-Julian Oscillations (MJO) observed in the terrestrial tropics
and are present in simulations applying prescribed and interactive
radiation, various orientation of CRCP domains (east-west versus
north-south), and various horizontal resolutions of the global model.
This presentation will focus on the sensitivity of these results to the
representation of cloud microphysics in the 2D cloud-resolving models
of CRCP.
Supplementary URL: