Subtropical Marine Low Stratiform Cloud Deck Spatial Errors in the E3SMv1 Atmosphere Model

Abstract

Marine low‐level clouds continue to be poorly simulated in models despite many studies and field experiments devoted to their improvement. Here we focus on the spatial errors in the cloud decks in the Department of Energy Earth system model (the Energy Exascale Earth System Model [E3SM]) relative to the satellite climatology by calculating centroid distances, area ratios, and overlap ratios. Since model dynamics is better simulated than clouds, these errors are attributed primarily to the model physics. To gain additional insight, we performed a sensitivity run in which model winds were nudged to those of reanalysis. This results in a large change (but not necessarily an improvement) in the simulated cloud decks. These differences between simulations are mainly due to the interactions between model dynamics and physics. These results suggest that both model physics (widely recognized) and its interaction with dynamics (less recognized) are important to model improvement in simulating these low‐level clouds.

An Overview of Atmospheric Features Over the Western North Atlantic Ocean and North American East Coast—Part 2: Circulation, Boundary Layer, and Clouds

“…Moreover, E3S-Mv1 is the only model evaluated here able to simulate the dynamical covariation in winter between cloud fraction and two atmospheric stability metrics. In addition, Brunke et al (2019) noted that interactions between large-scale dynamical motions and the parameterizations of subgrid-scale processes also contribute to errors in the simulation of clouds. This may be the reason for the slight differences between the clouds in E3SMv1 and CESM2.…”

“…In addition, Brunke et al. (2019) noted that interactions between large‐scale dynamical motions and the parameterizations of subgrid‐scale processes also contribute to errors in the simulation of clouds. This may be the reason for the slight differences between the clouds in E3SMv1 and CESM2.…”

An Introduction to the E3SM Special Collection: Goals, Science Drivers, Development, and Analysis

“…Journal of Advances in Modeling Earth Systems simulations analyzed and reported in this special collection include the ocean barrier layer (Reeves Eyre et al, 2019), stratocumulus clouds (Brunke et al, 2019), and monsoonal water cycle (Harrop et al, 2019).…”

Stratocumulus cloud clearings: statistics from satellites, reanalysis models, and airborne measurements

“…Various vertical levels were used for some MERRA-2 products as a way of obtaining representative information for different layers of the MBL and free troposphere (FT). Of note is that the MERRA-2 aerosol reanalysis relies on the GEOS-5 Goddard Aerosol Assimilation System (Buchard et al, 2015) for which the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) model (Chin et al, 2002) simulates 15 externally mixed aerosol tracers including sulfate, dust (five size bins), sea salt (five size bins), and hydrophobic and hydrophilic black carbon and organic carbon. Of relevance to this study, GOCART applies wind-speed-dependent emissions for sea salt.…”

“…Stratocumulus clouds also play an important role in the global radiation budget due to their high albedo contrast with the underlying ocean surface ( Hartmann and Short, 1980 ; Herman et al, 1980 ; Stephens and Greenwald, 1991 ). Challenges in accurately simulating the presence and properties of stratocumulus clouds include the difficulty in separating the influence of microphysical and dynamical factors and the existence of multiple feedbacks in cloud systems ( Brunke et al, 2019 ). Therefore, accurate characterization of cloud formation and evolution is critical.…”