To initialize the model, Doppler radar observations are used. Radar reflectivity and radial velocity are assimilated into the model using the adjoint technique. The assimilation system, which includes a cloud-scale model and its adjoints, determines the 3D wind, thermodynamical, and microphysical fields of the storm by minimizing the difference between radar observed variables and their model predictions.
Preliminary results show that using two volume scans of radar observations separated by 6 minutes, the retrieval is able to recover the band structure of the storm. The wind fields are reasonable and fit relatively well to the observed radial velocity. One hour forecasts of this event have been performed using the retrieved fields as initial conditions. Results show that the model simulates the motion of the snowband reasonably well. Work is currently being done to improve the microphysical representation in the model to allow a better quantitative snowfall forecast. We will also use the output from a mesoscale model to provide boundary conditions for the cloud-scale model so that the forecast can be extended beyond one hour.
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