Tropical Cirrus in Global Storm-Resolving Models. Part I: Role of Deep
Convection
Abstract
Pervasive cirrus clouds in the upper troposphere and tropical tropopause
layer (TTL) influence the climate by altering the top-of-atmosphere
radiation balance and stratospheric water vapor budget. These cirrus are
often associated with deep convection, which global climate models must
parameterize and struggle to accurately simulate. By comparing
high-resolution global storm-resolving models from the Dynamics of the
Atmospheric general circulation Modeled On Non-hydrostatic Domains
(DYAMOND) intercomparison that explicitly simulate deep convection to
satellite observations, we assess how well these models simulate deep
convection, convectively generated cirrus, and deep convective injection
of water into the TTL over representative tropical land and ocean
regions. The DYAMOND models simulate deep convective precipitation,
organization, and cloud structure fairly well over land and ocean
regions, but with clear intermodel differences. All models produce
frequent overshooting convection whose strongest updrafts humidify the
TTL and are its main source of frozen water. Inter-model differences in
cloud properties and convective injection exceed differences between
land and ocean regions in each model. We argue that global
storm-resolving models can better represent tropical cirrus and deep
convection in present and future climates than coarser-resolution
climate models. To realize this potential, they must use available
observations to perfect their ice microphysics and dynamical flow
solvers.