Search

We develop an algorithm to identify cold pools at the DOE's Eastern North Atlantic (ENA) site on Graciosa Island and examine the statistics of retrieved cold pools for the entire observational record from late 2016 to 2023. The retrieval strategy relies on leveraging above-background bivariate deviations in near-surface temperature and water vapor mixing ratio from the ENA station time series. Cold pools at ENA tend to be weak with a prominent annual cycle peaking in the cooler months and caused by reductions in the background turbulence during those months. Often, surface rain events are not associated with cold pools due to a combination of factors including but not limited to high background turbulence, high relative humidity, and low rain rate. The retrieval correctly identifies cold pools that are not associated with observed surface rain at the met station. Understanding the factors that lead to the formation of weak cold pools will lead to a greater understanding of the dynamics of the marine boundary layer at ENA and how those dynamics feed back to the cloud morphological structures. [ABSTRACT FROM AUTHOR]

Parameterized boundary layer turbulence and moist convection remain some of the largest sources of uncertainty in general circulation models. High-resolution climate modeling aims to reduce that uncertainty by explicitly attempting to resolve deep moist convective motions. An example of such a model is the Simple Cloud-Resolving E3SM Atmosphere Model (SCREAM) with a target global resolution of 3.25 km, allowing for a more accurate representation of complex mesoscale deep convective dynamics. Yet, small-scale planetary boundary layer turbulence and shallow convection still need to be parameterized, which in SCREAM is accomplished through the TKE-based Simplified Higher-Order Closure (SHOC)--a simplified version of the assumed doubled-Gaussian PDF higher-order closure method. In this paper, we implement a stochastic multiplume Mass-Flux (MF) parameterization of dry and shallow convection in SCREAM to go beyond the limitations of double-Gaussian PDF closures and couple it to SHOC (SHOC+MF). The new parameterization implemented in a single-column model type version of SCREAM produces results for two shallow cumulus convection cases (marine and continental shallow convection) that agree well with the reference large-eddy simulation data, thus improving the general representation of the thermodynamic quantities and their turbulent fluxes as well as cloud macrophysics in the model. Furthermore, SHOC+MF parameterization shows weak sensitivity to the vertical grid resolution and model time step. [ABSTRACT FROM AUTHOR]