Improving Bulk Microphysics Schemes for Deep Convective Systems Using MC3E Data

Principal Investigator(s):
Edward Zipser, University of Utah

There are five objectives for this project.

1. Primary Objective: Fully utilize all applicable high quality observations from the MC3E (2011) field campaign at the ARM Southern Great Plains site to evaluate cloud-resolving simulations, focusing on the performance of bulk microphysics schemes and the interaction of microphysics and dynamics, and how these affect larger-scale convective and stratiform structures.

2. Take advantage of the large spectrum of convective vertical velocities within the MC3E database to evaluate whether model simulations are able to capture this variety accurately, and if not, why not.

3. Compare these results with our research group’s previous simulations in the tropical monsoon region near Darwin Australia in the TWP-ICE campaign, and learn reasons for differences and/or similarities between these two differing large-scale regimes.

4. Identify problematic parts of microphysics schemes and develop scheme alterations to test the sensitivity of simulations to the identified problematic parts of microphysics schemes, focusing on two issues: Convective initiation and mesoscale system evolution, and dynamic-microphysical interactions in convective drafts and their relation to convective and stratiform structural properties.

5. Discuss implications for GCM convective and large-scale precipitation parameterizations as well as radiative impacts of anvil cirrus.

Our approach will begin by selecting three of the best-observed high priority MC3E case studies, for which quality-controlled observations will be available soonest. Using WRF, we will run several multinested limited area model simulations, being consistent with our TWP-ICE simulations. We shall use at least 10 different microphysics schemes, with specific focus on the 2-moment Morrison scheme, for which several variants have been established based on our TWP-ICE results. We will also test sensitivity to horizontal resolution because of its effect on resolved turbulent entrainment in convective drafts. The PI and members of his research group were at the SGP site covering the entire MC3E campaign, and we will use this knowledge to assemble all useful observations as they become available for critical comparisons with simulations. For example, we will be comparing the simulated convective vertical velocities with those derived from X-SAPR and C-SAPR multi-Doppler estimates. The PI will also acquire the HIWRAP vertical velocity data from ER-2 overflights of many of the convective storms, as well as the in situ microphysics data from the UND Citation, mostly within stratiform regions.

Our expected results will include sound evaluations of the strengths and weaknesses of numerous bulk microphysics schemes, and together with numerous informal collaborators, lead to specific proposed improvements, some of which we expect to test. Our careful evaluation of the products from the SGP ARM-acquired instrumentation may well lead to improvements in retrieval techniques, in collaboration with many of the VAP providers.

Major participants include the PI, Edward Zipser, with overall responsibility for supervision of project activities. Adam Varble is expected to complete his Ph.D. dissertation in December 2012, supported by this project, and if this proposal is accepted, to play a very important role in carrying out the modeling as outlined herein. At least one Graduate Research Assistant, most likely Sarah Bang, already familiar with the MC3E database, will be responsible for data analysis and assisting in detailed comparison with model output. While not named formally, we have numerous existing collaborations with the modeling community, including Steve Krueger (U. of Utah), Ann Fridlind (NASA GISS), Hugh Morrison (NCAR), and others. We also have many others assisting with QC and use of the MC3E data, including Scott Collis (ANL), Scott Giangrande/Mike Jensen (BNL), and numerous members of the NASA Science Team.