Convective Meteorology (Mesoscale Dynamics)

Evaluation of Unified Model (UM) microphysics using polarimetric radar observations and retrieved radar variables

Marcus Johnson

School Of Meteorology

12 February 2016, 3:00 PM

National Weather Center, Room 5600
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK

The UK Met Office Unified Model (UM) is being used by many weather forecasting agencies around the globe. This model is designed to run across spatial and time scales and known to produce reliable prediction for large-scale weather systems. However, the model has only recently begun running at high resolution with a horizontal grid spacing of 1.5 km. As its microphysics scheme is designed and tuned for large-scale precipitation systems, we investigate the performance of UM microphysics to determine both potential inherent biases or weaknesses that arise from the one-moment nature of the scheme. Three case studies are considered in this study: a changma (stationary) front, heavy rain, and Typhoon Sanba. UM model output is compared to observations using a polarimetric radar data simulator and retrieved radar variables. Initial results show that the UM model grossly overestimates rain number concentration, perhaps due to the diagnostic rain N0 formulation in the scheme. Further, the UM model generally fails to capture large rainwater content found in observations. In regard to convection, the model generally fails to replicate observed large-scale precipitation structure as model precipitation cores tend to be detached and isolated.

Convective Meteorology (Mesoscale Dynamics) Seminar Series website