A Simple Framework for Testing the Quality of Atmospheric Limited-Area Models

Abstract

A framework is designed for efficient experimentation with atmospheric forecast models on a limited area. It is shown that extended range atmospheric simulations on a limited area, using analyzed boundary values from a global model may be used as a tool to diagnose model deficiencies. Examples are given of model diagnosis on a limited area centered over Northern Europe, based on simulations with the High-Resolution Limited-Area Model over periods of one month. The effect of the lateral boundaries is investigated by comparing simulation results with forecasts from the global model up to a range of 10 days. The diagnosis is consistent with operational experiences with the limited-area model. The potential of the experimental framework is further investigated by testing the impact of two alternative parameterization schemes for radiation and condensation, respectively. The radiation scheme has not previously been tested in a forecast model. It is shown that these schemes have a marked positive impact on the model's vertical bias structure for temperature and humidity.