U.S. Department of Energy Office of Biological and Environmental Research

BER Research Highlights

Importance of Microphysical Processes in Simulating Tropical Mesoscale Convective Systems
Published: November 07, 2012
Posted: March 26, 2013

High clouds associated with tropical mesoscale convective systems (MCSs) can extend thousands of kilometers and last tens of hours, strongly impacting the global radiation budget. Accurately representing these clouds in climate models requires understanding of microphysical processes that control cloud properties and lifetime. U.S. Department of Energy scientists at Brookhaven National Laboratory and their collaborators performed cloud resolving model simulations using three microphysics parameterizations of varying complexity, evaluating them against satellite-retrieved cloud properties. A new algorithm to identify and track MCSs was also developed and applied to observations and model simulations over the Tropical Western Pacific (TWP) to track the full lifetime of individual cloud systems. The results demonstrated that MCS simulations are sensitive to microphysics parameterizations. The most crucial element was the fall velocity of frozen particles (i.e., ice, snow, and graupel). While model simulations all had similar updraft characteristics, microphysics parameterizations that produced particles with lower fall velocities produced a larger buildup of ice in the upper troposphere, leading to longer lasting and/or larger MCSs than observed in satellite observations. In terms of cloud properties, the performance of more complex two-moment schemes was not superior to that of the simpler one-moment schemes for these tropical cloud systems. This result indicates that improvements to microphysical parameterizations need to focus on better representation of processes such as ice nucleation and aggregation of ice crystals into snowflakes that affect number concentration in tropical high clouds.

Reference: Van Weverberg, K., A. M. Vogelmann, W. Lin, E. P. Luke, A. Cialella, P. Minnis, M. Khaiyer, E. Boer, and M. P. Jensen. 2013. “The Role of Cloud Microphysics Parameterization in the Simulation of Mesoscale Convective Systems and Anvil Clouds in the Tropical Western Pacific,” Journal of the Atmospheric Sciences, DOI: 10.1175/JAS-D-12-0104.1. (Reference link)

Contact: Dorothy Koch, SC-23.1, (301) 903-0105, Sally McFarlane, SC-23.1, (301) 903-0943
Topic Areas:

  • Research Area: Earth and Environmental Systems Modeling
  • Research Area: Atmospheric System Research
  • Facility: DOE ARM User Facility

Division: SC-23.1 Climate and Environmental Sciences Division, BER


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