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MS Defense

Department of Atmospheric Science

Thur., Nov. 29, 3:10 pm, EN6085

Modeling the Sensitivity of the February 22-24, 2017 Winter Storm to Microphysics Parameterization and Microphysics Processes over Colorado and Wyoming

Ethan Collins

University of Wyoming

Abstract

Accurate weather forecasts are crucial to the profitability of industry in the United States, such as the transportation of goods across the country via semi-trailer trucks. This topic is of particular concern over the state of Wyoming, as wintertime weather forecasts are often inadequate. Wyoming not only has a sparse network of surface and upper air observations but also complex terrain that cannot be properly represented in regional numerical models. Model forecast errors can have a substantial impact on the ability to issue advisories and close highways if necessary.

We focus on improving our understanding of why regional numerical weather prediction (NWP) models often fall short of predicting accurate snow totals via a case study that occurred on February 22-24, 2017. High-resolution simulations are run using the Weather Research and Forecasting (WRF) model. Four different microphysics parameterizations are utilized in this study: Thompson, Morrison two-moment, Predicted Particle Properties (P3), and the WRF Single-Moment 6-Class Scheme; the coupling between cloud properties and radiation as well as the role of latent heat release due to individual microphysical processes are also explored. The simulated precipitation is compared with both SNOTEL and PRISM data to quantify model errors and improvements using higher-resolution simulations and advanced microphysical parameterization.

The results support past studies which suggest that a dependency exists regarding the choice of microphysics parameterization and resolution over this region. All of the parameterizations utilized in this study overpredict snowfall accumulation; no clear bias as a function of altitude is identified. The coupling between the cloud microphysics and radiation is also found to have a minimal impact on storm strength, storm track, and snowfall amounts. Lastly, certain microphysical processes and the resultant latent heating are found to affect the storm characteristics.

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