Framework for improvement by vertical enhancement: A simple approach to improve representation of low and high‐level clouds in large‐scale models

Abstract

Low and high clouds of shallow extent, especially stratocumulus and even more so for high‐level cirrus clouds that reside where vertical resolution is particularly coarse, are poorly represented in large‐scale models such as global climate models and weather forecasting models. This adversely affects, among others, estimation of cloud feedbacks for climate prediction and weather forecasts. Here we address vertical resolution as a reason for the failure of these models to adequately represent shallow clouds. We introduce a new methodology, the Framework for Improvement by Vertical Enhancement (FIVE). FIVE computes selected processes on a one‐dimensional vertical grid with local high resolution in the boundary layer and near the tropopause. In addition to the host model, variables on the locally high‐resolution grid are predicted in parallel so that high‐resolution information is retained. By exchanging tendencies with one another, the host model and high‐resolution field are always synchronized. The methodology is demonstrated for drizzling stratocumulus capped by a sharp inversion. First, FIVE is applied to a single‐column model to identify the cause of biases associated with computing an assigned process at low resolution. Second, a two‐dimensional regional model coupled with FIVE is shown to produce results comparable to those performed with high vertical resolution. FIVE is thus expected to represent low clouds more realistically and hence reduce the low‐cloud bias in large‐scale models. Finally, we propose a number of methods that will be developed and tested to further optimize FIVE.

The Energy Exascale Earth System Model Simulations With High Vertical Resolution in the Lower Troposphere

“…The companion paper of Lee et al. (2021) addresses a potential solution, which involves the implementation of the Framework for Improvement by Vertical Enhancement (FIVE, Yamaguchi et al (2017)) to E3SM. The implementation of FIVE into E3SM will allow select physics processes to be run on a higher vertical resolution grid relative to the rest of model, which could provide a useful framework in obtaining similar results seen in this article but with a computation cost that is more digestible.…”

“…For example, while Bogenschutz et al (2012) found that the Community Atmosphere Model (CAM) coupled with CLUBB produces an improved simulation of stratocumulus and cumulus-under-stratocumulus regimes, compared to the control version of CAM when the standard 30 layer configuration was used, it wasn't until the vertical resolution was increased by a factor of four when cloud and temperature profiles more resembled those of observations and LES. Yamaguchi et al (2017) found substantial improvements in the simulated stratocumulus layer for CRMs when physics processes (including CLUBB) were run at much higher vertical grid than dynamical processes.…”

“…Yamaguchi et al. (2017) found substantial improvements in the simulated stratocumulus layer for CRMs when physics processes (including CLUBB) were run at much higher vertical grid than dynamical processes.…”

The Radiative Forcing of Aerosol–Cloud Interactions in Liquid Clouds: Wrestling and Embracing Uncertainty

“…In addition, the multiscale modeling framework (an embedded cloud resolving model within a GCM grid box) [48,104,111,117] provides a way forward. Vertical resolution is a persistent problem for shallow clouds, particularly stratocumulus, and new ideas have been proposed to locally apply an adaptive vertical mesh [85,159] …”

Marine Boundary Layer Clouds Associated with Coastally Trapped Disturbances: Observations and Model Simulations

“…To alleviate the computational expense of using a large number of vertical levels, new modeling techniques, such as the Framework for Improvement by Vertical Enhancement (FIVE;Yamaguchi et al 2017), may be incorporated in future efforts in which resolving strong vertical gradients is desired.…”