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3:30 p.m.
Atlantic Building Room 2400 & Zoom

AOSC Seminar by Dr. Greg Thompson, 2/24/2022

AOSC Seminar

Dr. Greg Thompson



Title: Using a Stochastic Parameter Perturbation to Represent Process-Based Uncertainty in a Microphysics Parameterization


Most regional NWP model ensemble systems are under-dispersive, producing unreliable and overconfident ensemble forecasts (e.g., Buizza et al. 2005, Romine et al. 2015, Jankov et al. 2017, 2019).  Besides initial and boundary condition uncertainties, other sources of error are contained within a model's physical parameterization schemes.  Whether considering a model's radiation, cumulus, boundary-layer, land-surface, or microphysics scheme, each has a plethora of internal constants or diagnosed variables that are known to vary widely yet were typically picked from prior literature as constants.  For this reason, Berner et al. (2009, 2015) created a stochastic pattern generator to perturb various parameters within physical parameterization schemes.  The stochastic parameter perturbation (SPP) method has been used by Jankov et al. (2017, 2019) to introduce perturbations to the land-surface and planetary boundary-layer scheme and by Griffin et al. (2019) to perturb the microphysics scheme.  In these studies, various number of ensemble members were compared with typical weather observations such as near-surface and upper-level temperature and winds, radar reflectivity, quantitative precipitation forecasts and satellite brightness temperatures.

In this talk, we will present the methods and outcomes of three applications of SPP within the Thompson and Eidhammer (2014) aerosol-aware microphysics scheme in the Weather Research and Forecasting (WRF) model.  The three aspects were specifically chosen as they involve perhaps the most highly uncertain internal elements in the scheme:  1) the size distribution of cloud droplets; 2) the size distribution of graupel/hail; 3) the activation of cloud condensation and ice nuclei.



Dr. Greg Thompson is a research scientist at the Joint Center for Satelite Data assimilation, where he uses his expertise in cloud microphysics to improve satellite data assimilation capabilities for numerical weather prediction. Greg earned his B.S. in meteorology from Pennsylvania State University in 1990, his M.S. in atmospheric science from Colorado State University in 1993, and his Doctor of Philosophy in Atmospheric Science from the University of Colorado. He is internationally recognized for his research on numerical weather modeling, particularly the parameterization of cloud physics and precipitation processes. He developed a bulk microphysical parameterization that is widely used in community weather models. The latest version of the now aerosol-aware Thompson-Eidhammer microphysics scheme is operationally used in the Rapid Refresh (RAP) and High-Resolution Rapid Refresh (HRRR) models run at the National Center for Environmental Prediction (NCEP). Simultaneous to improving cloud physics parameterizations in weather models, Greg has greatly contributed towards the development of automated aircraft and ground icing forecast applications using model output and explicit prediction of super-cooled liquid water together with various surface, radar, and multispectral satellite data to create icing hazard guidance products that are now routinely generated by NCEP to serve the aviation industry. In addition, Greg pioneered the automation and delivery of weather data and graphics to the web starting in 1994 with the NCAR RAP/RAL Real-Time Weather Data website. The immediate success of this site led to the Aviation Digital Data Service (ADDS) project. Under Greg’s leadership, the ADDS team successfully delivered the first-ever NCAR technology transfer of operational systems to the National Weather Service, where it continues to run today. The ADDS team won the UCAR Outstanding Technical Achievement award in 1999, as well as a U.S. Government Technology Achievement award in 2000.


Contact: Jonathan Poterjoy

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AOSC Seminar

Pre-seminar refreshment: N/A
Seminar: 3:30-4:30pm, Room: ATL 2400(only when in-person)
Meet-the-Speaker: 4:30-5:00pm, Room: ATL 3400(only when in-person) [For AOSC Students only]

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