Tropical Cirrus in Global Storm-Resolving Models. Part II: Cirrus Life
Cycle and Top-of-Atmosphere Radiative Fluxes
Cirrus clouds of various thicknesses and radiative characteristics
extend over much of the tropics, especially around deep convection. They
can be difficult to observe due to their high altitude and sometimes
small optical depths.
They are also difficult to simulate in conventional global climate
models, which have coarse grid spacings and simplified parameterizations
of deep convection and cirrus formation.
We investigate the representation of tropical cirrus in global
storm-resolving models (GSRMs), which have higher spatial resolution and
explicit convection and could more accurately represent cirrus cloud
processes. This study uses GSRMs from the DYnamics of the Atmospheric
general circulation Modeled On Non-hydrostatic Domains (DYAMOND)
project. The aggregate life cycle of tropical cirrus is analyzed using
joint albedo and outgoing longwave radiation (OLR) histograms to assess
the fidelity of models in capturing the observed cirrus cloud
populations over representative tropical ocean and land regions. The
proportions of optically-thick deep convection, anvils, and cirrus vary
across models and are reflected in the vertical distribution of cloud
cover and top-of-atmosphere radiative fluxes. Model differences in
cirrus populations, likely driven by sub-grid processes such as ice
microphysics, dominate over regional differences between
convectively-active tropical land and ocean locations.