The Research Of Model Perturbation On T213Ensemble Model Of15-day Integration

Research and application of model perturbation is a hot issue of ensemble forecastingperturbation technique, while the development of extension period ensemble forecasting isalso one of the goals of the world’s major numerical prediction center. This article referred tothe model stochastic perturbation scheme in European Center for Medium-range WeatherForecasts, based on our T213global medium-term ensemble forecast system, designed twodifferent model stochastic perturbation schemes, the first scheme introduced perturbation onthe total tendency of physical processes and dynamic processes (referred STPS),the secondscheme perturbed only on the tendency of parameterized physical process (referredSPPS).First,These two schemes are introduced into ensemble model to perform a summernumerical test, the forecast performance of these two schemes are validated, and the ability ofSPPS scheme for winter forecast and heavey rainfall forecast are valued. Then thecharacteristics of SPPS scheme are discussed.In addition, the performance of15-dayintertration ensemble forecast with SPPS scheme has been analysed.(1) Although STPS scheme has the advantages on reducing the rooth mean square error inthe region of tropical and East Asian, SPPS scheme can improve the spread of summerensemble forecasts in the region of Northern and Southern hemisphere, East Asian andTropical, and reduce the forecast root mean square error in the region of Southern andNorthern hemisphere,when compared with STPS scheme.Both two schemes can not improveall the accuracy score at the same time, but the brier score (BS) and continous rankedprobability score (CRPS) of ensemble forecast of500hPa geopetential height and250hPawind is significantly improved with the SPPS scheme.(2) SPPS scheme can improve the spread of winter forecast in above four regions slightly,but it has no significant improvement in the root mean square error.The BS and CRPS ofwinter forecasts for250hPa wind is improved most significantly with SPPS scheme. And theBS and CRPS of winter forecast for500hPa geopetential height is improved significantlybefore5-day integration. But the improvement of850hPa temperature forecast accuracyscore is not significant.T213global medium-term ensemble forecast model by addingstochastic physical perturbation scheme(SPPS), can enhance the intensity forecast of heavyrainfall center and improve the precipitation score of moderate rain.Besides,the probabilisticprediction skill of precipitation forecast can been improved to a certain degree.(3) SPPS scheme can reasonably reflect the model uncertainty.Beisides, there are similarities and differences in the perturbation characteristics between winter forecast andsummer forecast with SPPS scheme.In addition, The total perturbation energy of SPPSscheme has a character that propagates from small scale to large scale with increasingintegration time.(4) The accuracy of15-day integration daily ensemble forecast with SPPS scheme is muchbetter than the deterministic model.Besides,5-day mean ensemble forecast is more crediblethan daily ensemble forecast in10-15day period.