A Lagrangian perspective on tropical anvil cloud lifecycle in present
and future climate
- Blaz Gasparini,
- Philip J. Rasch,
- Dennis L. Hartmann,
- Casey James Wall,
- Marina Duetsch
Philip J. Rasch
Pacific Northwest National Laboratory (DOE), Pacific Northwest National Laboratory (DOE)
Author ProfileDennis L. Hartmann
University of Washington, University of Washington
Author ProfileCasey James Wall
Scripps Institution of Oceanography, Scripps Institution of Oceanography
Author ProfileMarina Duetsch
University of Washington, University of Washington
Author ProfileAbstract
The evolution of tropical anvil clouds from their origin in deep
convective cores to their slow decay determines the climatic effects of
clouds in tropical convective regions. Despite the relevance of anvil
clouds for climate and responses of clouds to global warming, processes
dominating their evolution are not well understood. Currently available
observational data reveal instantaneous snapshots of anvil cloud
properties, but cannot provide a process-based perspective on anvil
evolution. We therefore conduct simulations with the high resolution
version of the Exascale Earth System Model in which we track mesoscale
convective systems over the Tropical Western Pacific and compute
trajectories that follow air parcels detrained from peaks of convective
activity. With this approach we gain new insight into the anvil cloud
evolution both in present day and future climate. Comparison with
geostationary satellite data shows that the model is able to simulate
maritime mesoscale convective systems reasonably well. Trajectory
results indicate that anvil cloud lifetime is about 15 hours with no
significant change in a warmer climate. The anvil ice water content is
larger in a warmer climate due to a larger source of ice by detrainment
and larger depositional growth leading to a more negative net cloud
radiative effect along detrained trajectories. However, the increases in
sources are counteracted by increases in sinks of ice, particularly snow
formation and sedimentation. Furthermore, we find that the mean anvil
cloud feedback along trajectories is positive and consistent with
results from more traditional cloud feedback calculation methods.27 Feb 2021Published in Journal of Geophysical Research: Atmospheres volume 126 issue 4. 10.1029/2020JD033487