Mesoscale Convective Systems tracking Method Intercomparison (MCSMIP):
Application to DYAMOND Global km-scale Simulations
Abstract
Global kilometer-scale models are the future of Earth system models as
they can explicitly simulate organized convective storms and their
associated extreme weather. Here, we comprehensively examined tropical
mesoscale convective system (MCS) characteristics in the DYAMOND
(DYnamics of the atmospheric general circulation modeled on
non-hydrostatic domains) models for both summer and winter phases by
applying eight different feature trackers to the simulations and
satellite observations. Although different trackers produce substantial
differences (a factor of 2-3) in observed MCS frequency and their
contribution to total precipitation, model-observation differences in
MCS statistics are more consistent among the trackers. DYAMOND models
are generally skillful in simulating tropical mean MCS frequency, with
multi-model mean biases of 2.9% over land and -0.5% over ocean.
However, most models underestimate the MCS precipitation amount (23%)
and their contribution to total precipitation (17%) relative to
observations. These biases show large inter-model variability, but are
generally smaller over land (13%) than over ocean (21%) on average.
MCS diurnal cycle and cloud shield characteristics are better simulated
than precipitation. Most models overestimate MCS precipitation intensity
and underestimate stratiform rain contribution (up to a factor of 2),
particularly over land. Models also predict a wide range of precipitable
water in the tropics compared to reanalysis and satellite observations,
and many models simulate a greater sensitivity of MCS precipitation
intensity to precipitable water. The MCS metrics developed in this work
provide process-oriented diagnostics for future model development
efforts.