Climate Prediction and Diagnostic Analysis of Typhoon Precipitation in Midsummer of Yongzhou

By consulting the typhoon yearbook and restoring the historical weather chart,technical separation of typhoon precipitation in Yongzhou from July to September of 1981-2015 was conducted.On this basis,climatic characteristics of typhoon precipitation in midsummer of Yongzhou were analyzed,and climate prediction and diagnostic analysis were carried out.The research results showed that typhoon precipitation was an important component of midsummer precipitation in Yongzhou,but its contribution to total precipitation was not as much as precipitation of the westerly belt system.When the ridge line of the western Pacific subtropical high was northward,typhoon precipitation was more than westerly precipitation in midsummer of Yongzhou;when the subtropical high was southward,there were more patterns of westerly precipitation year;when the subtropical high was normally northward,typhoon precipitation and westerly precipitation were less,with more dry years.In summer,abnormal cold sea surface temperature(SST)in tidal zone and warm pool zone of western Pacific and abnormal warm SST in NinoZ zone(strong El Nino event)were favorable for that the ridge line of the western Pacific subtropical high was southward,and there were more patterns of westerly precipitation year in midsummer of Yongzhou.On the contrary,when subtropical high was northward or normally northerly,there was less westerly precipitation.In non La Nina years when the subtropical high was northward,most of them were typhoon precipitation years.In La Nina years when the subtropical high was northward,most of them were dry years.

BMA probability quantitative precipitation forecasting of land-falling typhoons in south-east China

The probability of quantitative precipitation forecast(PQPF)of three Bayesian Model Averaging(BMA)models based on three raw super ensemble prediction schemes(i.e.,A,B,and C)are established,which through calibration of their parameters using 1-3 day precipitation ensemble prediction systems(EPSs)from the China Meteorological Administration(CMA),the European Centre for Medium-Range Weather Forecasts(ECMWF)and the National Centers for Environmental Prediction(NCEP)and observation during land-falling of three typhoons in south-east China in 2013.The comparison of PQPF shows that the performance is better in the BMA than that in raw ensemble forecasts.On average,the mean absolute error(MAE)of 1 day lead time forecast is reduced by 12.4%,and its continuous ranked probability score(CRPS)of 1-3 day lead time forecast is reduced by 26.2%,respectively.Although the amount of precipitation prediction by the BMA tends to be underestimated,but in view of the perspective of probability prediction,the probability of covering the observed precipitation by the effective forecast ranges of the BMA are increased,which is of great significance for the early warning of torrential rain and secondary disasters induced by it.

Interaction Between Typhoon Vicente(1208) and the Western Pacific Subtropical High During the Beijing Extreme Rainfall of 21 July 2012

The heaviest rainfall in recent six decades fell in Beijing on 21 July 2012, reaching a record of 460 mm within 18 h. This rainfall was a typical remote precipitation event related to Typhoon Vicente（1208）.Observational analysis indicates that Vicente influenced distant heavy rainfall by transporting water vapor northward to the Beijing area. This moisture transport was mainly driven by the interaction between Vicente and the western Pacific subtropical high（WPSH） associated with the formation of a low-level southeasterly moisture channel. A set of numerical sensitivity experiments were performed with prescribed typhoons of different intensities to investigate the interaction between Vicente and the WPSH and its effects on this rainstorm process. The results indicate that the WPSH interacting with typhoons of different intensities may exert varying degrees of influence on the development of a southeasterly moisture channel, resulting in a change in rain rate and location over the Beijing area. Specifically, in the presence of an enhanced typhoon,the WPSH shows remarkable withdrawal to the east, which is favorable for a northward extension of the southeasterly moisture channel, thereby increasing moisture supply for the rainstorm. The WPSH tends to stretch westward in a zonal pattern if the typhoon is weakened or removed, hindering the northward extension of the moisture channel. Thus, the rainfall area may be expected to expand or contract, with corresponding increases or decreases in rain rate over the Beijing area with a strengthened or weakened typhoon, respectively.