The role of cloud microphysics parameterization in the simulation of mesoscale convective systems in the Tropical Western Pacific

 
Poster PDF

Authors


Andrew M. Vogelmann — Brookhaven National Laboratory
Wuyin Lin — Brookhaven National Laboratory
Edward Luke — Brookhaven National Laboratory
Alice T. Cialella — Brookhaven National Laboratory
Patrick Minnis — NASA - Langley Research Center
Mandana Khaiyer — Science Systems and Applications, Inc. (SSAI)
Erwin Boer — LUEBEC
Michael Jensen — Brookhaven National Laboratory

Category

Modeling

Description

High clouds, related to tropical convection, have been a challenge to climate modeling ever since its inception, even as the representation of clouds improved and grid spacings became smaller over the years. Progress in the representation of convective cloud structures within cloud-resolving models can only be achieved if the physical reasons for discrepancies between the different models are truly understood. This poster presents a detailed analysis of convection-permitting cloud simulations, aimed at increasing the understanding of the role of parameterized cloud microphysics in the simulation of mesoscale convective systems (MCSs) in the Tropical Western Pacific (TWP). Simulations using three commonly used cloud parameterizations with varying complexity have been compared against satellite-retrieved cloud properties. An MCS identification and tracking algorithm was applied to the observations and the simulations to evaluate the number, spatial extent, and microphysical properties of individual cloud systems. Different from previous studies, these individual cloud systems could be tracked over larger distances due to the large TWP domain studied. The analysis demonstrates that the simulation of MCSs is very sensitive to the parameterization of microphysical processes. The most crucial element was found to be the fall velocity of frozen condensate. Differences in this fall velocity between the experiments were more related to differences in particle number concentrations than to fall speed parameterization. Microphysics schemes that exhibit slow sedimentation rates for ice aloft experience a larger buildup of condensate in the upper troposphere. This leads to more numerous and/or larger MCSs with larger anvils. Surface precipitation was found to be overestimated and insensitive to the microphysical schemes employed in this study. In terms of the investigated properties, the performance of complex two-moment schemes was not superior to the simpler one-moment schemes, since explicit prediction of number concentration does not necessarily improve processes such as ice nucleation, the aggregation of ice crystals into snowflakes, and their sedimentation characteristics.

Van Weverberg, K, AM Vogelmann, W Lin, EP Luke, A Cialella, P Minnis, M Khaiyer, ER Boer, and MP Jensen. 2013. “The role of cloud microphysics parameterization in the simulation of mesoscale convective system clouds and precipitation in the Tropical Western Pacific.” Journal of the Atmospheric Sciences, in press.