Abstract
This paper describes the first implementation of the d x=3.25 km version
of the Energy Exascale Earth System Model (E3SM) global atmosphere model
and its behavior in a 40 day prescribed-sea-surface-temperature
simulation (Jan 20-Feb 28, 2020). This simulation was performed as part
of the DYnamics of the Atmospheric general circulation Modeled On
Non-hydrostatic Domains (DYAMOND) phase 2 model intercomparison.
Effective resolution is found to be $\sim 6x the
horizontal grid resolution despite using a coarser grid for physical
parameterizations. Despite this new model being in an immature and
untuned state, moving to 3.25 km grid spacing solves several
long-standing problems with the E3SM model. In particular, Amazon
precipitation is much more realistic, the frequency of light and heavy
precipitation is improved, agreement between the simulated and observed
diurnal cycle of tropical precipitation is excellent, and the vertical
structure of tropical convection and coastal stratocumulus look good. In
addition, the new model is able to capture the frequency and structure
of important weather events (e.g. hurricanes, midlatitude storms
including atmospheric rivers, and cold air outbreaks). Interestingly,
this model does not get rid of the erroneous southern branch of the
intertropical convergence zone nor the tendency for strongest convection
to occur over the Maritime Continent rather than the West Pacific, both
of which are classic climate model biases. Several other problems with
the simulation are identified, underscoring the fact that this model is
a work in progress.