engleski

Skill of 2-m Temperature Seasonal Forecasts over Europe in ECMWF and RegCM Models

The 50-km Regional Climate Model (RegCM3) is used to dynamically downscale 9-member ensembles of ECMWF global experimental seasonal forecasts over Europe for winter and summer seasons during the period 1991 to 2001. Three sets of RegCM3 experiments with different soil moisture initializations are performed: the RegCM3 default initial soil moisture which is based on vegetation and soil type, seasonally and annually varying initial soil moisture taken from ECMWF seasonal forecasts and initial soil moisture obtained from RegCM3 ERA-Interim driven integrations (RegCM3 climatology). Both deterministic and probabilistic measures of forecast quality are analyzed for 2-m temperature seasonal forecasts. The impact of initial soil moisture on RegCM3 forecast skill is seen in summer in the relatively dry southern part of the integration domain. When regional model soil moisture was initialized from ECMWF seasonal forecasts, systematic errors are reduced and deterministic skill is enhanced relative to the other RegCM3 experiments. There is no major impact of soil moisture initialization on forecast skill in winter. However, some significant improvements in RegCM3 probabilistic skill scores for positive anomalies in winter are found in the central part of the domain where RegCM3 systematic errors are smaller than in global model. Although the 2-m temperature systematic errors in RegCM3 are generally not much reduced when compared to ECMWF model, in regions and seasons where such a reduction of errors is seen, the deterministic and probabilistic skill of regional model is improved relative to the global model.

seasonal forecasts; dynamical downscaling; RegCM

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