Towards a Unified Setup to Simulate Mid-Latitude and Tropical Mesoscale
Convective Systems at Kilometer-Scales
Abstract
Mesoscale convective systems (MCSs) are the main source of precipitation
in the tropics and parts of the mid-latitudes and are responsible for
high-impact weather worldwide. Studies showed that deficiencies in
simulating mid-latitude MCSs in state-of-the-art climate models can be
alleviated by kilometer-scale models. However, whether these models can
also improve tropical MCSs and weather we can find model settings that
perform well in both regions is understudied. We take advantage of
high-quality MCS observations collected over the Atmospheric Radiation
Measurement (ARM) facilities in the U.S. Southern Great Plains (SGP) and
the Amazon basin near Manaus (MAO) to evaluate a perturbed physics
ensemble of simulated MCSs with 4\,km horizontal grid
spacing. A new model evaluation method is developed that enables to
distinguish biases stemming from spatiotemporal displacements of MCSs
from biases in their reflectivity and cloud shield. Amazon MCSs are
similarly well simulated across these evaluation metrics than SGP MCSs
despite the challenges anticipated from weaker large-scale forcing in
the tropics. Generally, SGP MCSs are more sensitive to the choice of
model microphysics, while Amazon cases are more sensitive to the
planetary boundary layer (PBL) scheme. Although our tested model physics
combinations had strengths and weaknesses, combinations that performed
well for SGP simulations result in worse results in the Amazon basin and
vice versa. However, we identified model settings that perform well at
both locations, which include the Thompson and Morrison microphysics
coupled with the Yonsei University (YSU) PBL scheme and the Thompson
scheme coupled with the Mellorâ\euro“Yamadaâ\euro“Janjic (MYJ) PBL
scheme.