A possible approach for the extended-range forecast of winter minimum temperature over Southern China
Extended-range forecast of the next 10～30 days has been a persistent challenge.In this study,a leading 25 days extension prediction model is constructed for the winter minimum temperature(Tmin)over southern China where is extremely sensitive to extreme low temperature events.The winter daily datasets during 1979/1980-2019/2020 are from the fifth generation ECMWF reanalysis.The pentad increment method is suggested to build the forecast model,in which 5 pentad increment is calculated by subtracting the leading 5 pentad value from the current day value.Compared to the original format,the pentad increment format can amplify and extend the prediction signal at the intraseasonal scale.The soil temperature and the 50 hPa geopotential height in the stratosphere are chose as predictors.They can modulate the Tmin by influencing the circulation anomalies in Siberia,the North Atlantic Oscillation,and the Eurasian teleconnection pattern.Based upon the quasi-50-days periodicity and 5 pentad significant autocorrelation,above two predictors in the pentad increment format can skillfully predict the pentad increment of Tmin at leading 5 pentads(PI_Tmin).The predicted PI_Tmin is add to the observation at 5 pentad ago to obtained final predicted Tmin.During the independent hindcast period of 2009/2010-2019/2020 winter,the correlation skill of Tmin is 0.45 and the hit rate for extreme cold days is 57％.The incremental method used in this study can provide new ideas for the extension period forecasting of current extreme weather events.
NETL
NSTL
万方数据
