Using the ARM-SGP variational analysis to evaluate a PDF-based parameterization for boundary layers and clouds

 

Authors

Leo Donner — Geophysical Fluid Dynamics Laboratory
Yanluan Lin — Tsinghua University

Category

Modeling

Description

Single-column model (SCM) studies with a parameterization for boundary layers and associated clouds, based on multi-variate probability density functions including dynamics (MVD PDFs), have shown great promise in simulating cloud microphysics, macrophysics, and cloud-aerosol interactions. These studies have used Global Cloud System Study (GCSS) test cases for cumulus, stratocumulus, and mixed cloud types. In this study, we report on our tests of MVD PDFs using the ARM variational analysis for the SGP site. While the MVD PDFs simulate clouds when applied to the GCSS sounding and forcings, they do not do so when applied for corresponding periods to the ARM variational analysis. We examine the roles of the ARM-GCSS differences in surface fluxes, temperature and moisture advection, and initial soundings in explaining the behavior of the MVD PDFs. We will explore the possibility that horizontal averaging of vertical structures in the fields driving the MVD PDFs is responsible for the degraded performance of the MVD PDFs using the ARM analysis and the prospects for improving their performance using smaller-scale ARM observations.