An approach is proposed for predicting turning and acceleration motion trend of the tropical cyclones over the South China Sea for 72 h in the extrapolated track coordinates.Cross-track (CT)and along-track(AT)componen...An approach is proposed for predicting turning and acceleration motion trend of the tropical cyclones over the South China Sea for 72 h in the extrapolated track coordinates.Cross-track (CT)and along-track(AT)components are defined according to the persistently extrapolated track coodinates based on observed positions at the initial and past 24 h times.A kind of straight- forward measure may be provided with CT and AT components for typhoon turning motion and ac- celeration motion.Canonical correlation analysis(CCA)is performed to reveal the correlaotions be- tween tropical cyclone tracks and environmental 500 hPa geopotential height fields.A stepwise dis- criminate analysis technique is adopted to derive the classification functions of the respective three categories for AT and CT components.Especially,categorical combinations of CT and AT compo- nents are divided into possible 9 regions corresponding with tropical cyclone behaviors.Not only can 9 motion trends of a tropical cyclone be predicted,but also the location and its maximum error at least in certain direction are available.The perfect prediction(PP)verifications indicate that the percent corrects for the CT and AT categories are 67% and 69% in the independent samples,73% and 53% in the dependent samples,respectively,higher than that of 33.3% for random chance; moreover,the rate for successfully forecasting that in which one of the nine regions the tropical cy- clones will fall at 72 h is about 40%,also higher than the stochastic probability of 11%.The method has been proved to be skillful and promising.展开更多
利用2001年7月至2011年7月甘肃省榆中县地面观测站每日8次云量资料和同期NCEP每日4次等压面资料,由NCEP资料构造预报因子,以总云量和低云量为预报对象,分析预报因子和预报对象的相关性,采用逐步回归方法建立榆中县逐月每日8个时次的云...利用2001年7月至2011年7月甘肃省榆中县地面观测站每日8次云量资料和同期NCEP每日4次等压面资料,由NCEP资料构造预报因子,以总云量和低云量为预报对象,分析预报因子和预报对象的相关性,采用逐步回归方法建立榆中县逐月每日8个时次的云量预报方程并进行回代;并利用2012年的资料检验预报方程的预报效果。结果表明:云量主要受整层湿度、垂直运动、不稳定能量、槽强度指数和700 h Pa水汽通量散度影响,其中湿度条件和垂直运动是重要因素。建立的预报方程对总云量的预报效果比低云量好;总云量平均预报误差在2成左右,低云量平均预报误差在3成左右;预报值的变化趋势可以部分地反映实际云量的变化趋势。展开更多
文摘An approach is proposed for predicting turning and acceleration motion trend of the tropical cyclones over the South China Sea for 72 h in the extrapolated track coordinates.Cross-track (CT)and along-track(AT)components are defined according to the persistently extrapolated track coodinates based on observed positions at the initial and past 24 h times.A kind of straight- forward measure may be provided with CT and AT components for typhoon turning motion and ac- celeration motion.Canonical correlation analysis(CCA)is performed to reveal the correlaotions be- tween tropical cyclone tracks and environmental 500 hPa geopotential height fields.A stepwise dis- criminate analysis technique is adopted to derive the classification functions of the respective three categories for AT and CT components.Especially,categorical combinations of CT and AT compo- nents are divided into possible 9 regions corresponding with tropical cyclone behaviors.Not only can 9 motion trends of a tropical cyclone be predicted,but also the location and its maximum error at least in certain direction are available.The perfect prediction(PP)verifications indicate that the percent corrects for the CT and AT categories are 67% and 69% in the independent samples,73% and 53% in the dependent samples,respectively,higher than that of 33.3% for random chance; moreover,the rate for successfully forecasting that in which one of the nine regions the tropical cy- clones will fall at 72 h is about 40%,also higher than the stochastic probability of 11%.The method has been proved to be skillful and promising.
文摘利用2001年7月至2011年7月甘肃省榆中县地面观测站每日8次云量资料和同期NCEP每日4次等压面资料,由NCEP资料构造预报因子,以总云量和低云量为预报对象,分析预报因子和预报对象的相关性,采用逐步回归方法建立榆中县逐月每日8个时次的云量预报方程并进行回代;并利用2012年的资料检验预报方程的预报效果。结果表明:云量主要受整层湿度、垂直运动、不稳定能量、槽强度指数和700 h Pa水汽通量散度影响,其中湿度条件和垂直运动是重要因素。建立的预报方程对总云量的预报效果比低云量好;总云量平均预报误差在2成左右,低云量平均预报误差在3成左右;预报值的变化趋势可以部分地反映实际云量的变化趋势。
