Based on the data of daily precipitation in Lianyungang area from 1951 to 2012 and various climate signal data from the National Climate Center website and the NOAA website,a model for predicting whether the number of...Based on the data of daily precipitation in Lianyungang area from 1951 to 2012 and various climate signal data from the National Climate Center website and the NOAA website,a model for predicting whether the number of rainstorm days in summer in Lianyungang area is large was established by the classical C5. 0 decision tree algorithm. The data samples in 48 years( accounting for about 80% of total number of samples)was as the training set of a model,and the training accuracy rate of the model was 95. 83%. The data samples in the remaining 14 years( accounting for about 20% of total number of samples) were used as the test set of the model to test the model,and the test accuracy of the model was 85. 71%. The results showed that the prediction model of number of rainstorm days in summer constructed by C5. 0 algorithm had high accuracy and was easy to explain. Moreover,it is convenient for meteorological staff to use directly. At the same time,this study provides a new idea for short-term climate prediction of number of rainstorm days in summer.展开更多
Extremely heavy rainstorm occurred in Beijing on July 21,2012, which was the most serious since 1961. Based on analyzing the precipitation characteristics, formation mechanism of the rainstorm process was analyzed. Re...Extremely heavy rainstorm occurred in Beijing on July 21,2012, which was the most serious since 1961. Based on analyzing the precipitation characteristics, formation mechanism of the rainstorm process was analyzed. Results showed that when the precipitation process occurred, it was stable east-high and west-low situation at 500 hPa, and there was a steady stream of water vapor transportation at middle and low layers and strong vertical ascending motion at 700 hPa. The distribution of physical quantity field （relative humidity, vorticity and divergence） showed that they were all benefited to the formation of rainstorm. Then, falling zone of rainstorm and the movement of rain belt, generation, development and weakening of precipitation were analyzed. Finally, according to circulation situation and the distribution of physical quantity at each layer, vertical distribu- tion of physical quantity and distribution of water vapor and jet stream, ＂7 · 21＂ rainstorm model was summarized.展开更多
By using the durative rainstorm data in South China during May-early June in 2010,the forecast characteristics of K index and low level jet were analyzed.The results found that K2 had the good indication,advancement a...By using the durative rainstorm data in South China during May-early June in 2010,the forecast characteristics of K index and low level jet were analyzed.The results found that K2 had the good indication,advancement and relativity on the intensity and falling zone forecast of regional rainstorm in future 24 h,and the positive relative coefficient reached 0.987.The low level jet also had the same advancement and indication significance on the intensity and influence scope of regional rainstorm in 24 h in the future,and the relative coefficient reached above 0.8.K2 and the low level jet were selected as the main factors,and the basic conceptual model of rainstorm falling zone was established.The model has passed the computer program and realized the business automation.K2 provided the important basis for the forecast of rainstorm intensity and falling zone.展开更多
The numerical forecasts of mei-yu front rainstorms in China has been an important issue. The intensity and pattern of the frontal rainfall are greatly influenced by the initial fields of the numerical model. The 4-dim...The numerical forecasts of mei-yu front rainstorms in China has been an important issue. The intensity and pattern of the frontal rainfall are greatly influenced by the initial fields of the numerical model. The 4-dimensional variational data assimilation technology (4DVAR) can effectively assimilate all kinds of observed data, including rainfall data at the observed stations, so that the initial fields and the precipitation forecast can both be greatly improved. The non-hydrostatic meso-scale model (MM5) and its adjoint model are used to study the development of the mei-yu front rainstorm from 1200 UTC 25 June to 0600 UTC 26 June 1999. By numerical simulation experiments and assimilation experiments, the T106 data and the observed 6-hour rainfall data are assimilated. The influences of many factors, such as the choice of the assimilated variables and the weighting coefficient, on the precipitation forecast results are studied. The numerical results show that 4DVAR is valuable and important to mei-yu front rainfall prediction.展开更多
The authors use numerical model integral products in a third level forecast of synthetically multi-level analog forecast technology.This is one of the strongest points of this study,which also includes the re-ducing m...The authors use numerical model integral products in a third level forecast of synthetically multi-level analog forecast technology.This is one of the strongest points of this study,which also includes the re-ducing mean vacant-forecast rate method,which pos-sesses many advantages with regard to filtering the analog term.Moreover,the similitude degree between samples is assessed using a combination of meteorological elements,which works better than that described using a single element in earlier analog forecast studies.Based on these techniques,the authors apply the model output,air sounding,surface observation and weather map data from 1990 to 2002 to perform an analog experiment of the quasi-stationary front rainstorm.The most important re-sults are as follows:(1) The forecast successful index is 0.36,and was improved after the forecast model was re-vised.(2) The forecast precise rate (0.59) and the lost-forecast rate (0.33) are also better than those of other methods.(3) Based on the model output data,the syn-thetically multilevel analog forecast technology can pro-duce more accurate forecasts of a quasi-stationary front rainstorm.(4) Optimal analog elements reveal that trig-gering mechanisms are located in the lower troposphere while upper level systems are more important in main-taining the phase of the rainstorm.These variables should be first taken into account in operational forecasts of the quasi-stationary front rainstorm.(5) In addition,experi-ments reveal that the position of the key zone is mainly decided by the position of the system causing the heavy rainfall.展开更多
基金Support by Meteorological Open Research Foundation for the Huaihe River Basin(HRM201602)Foundation for Young Scholars of Jiangsu Meteorological Bureau(Q201708,KQ201802)+2 种基金Science and Technology Innovation Team Foundation for Marine Meteorological Forecast Technology of Lianyungang Meteorological BureauKey Technology R&D Program Project of Lianyungang City(SH1634)Special Project for Forecasters of Jiangsu Meteorological Bureau(JSYBY201811,JSYBY201812,JSYBY201810)
文摘Based on the data of daily precipitation in Lianyungang area from 1951 to 2012 and various climate signal data from the National Climate Center website and the NOAA website,a model for predicting whether the number of rainstorm days in summer in Lianyungang area is large was established by the classical C5. 0 decision tree algorithm. The data samples in 48 years( accounting for about 80% of total number of samples)was as the training set of a model,and the training accuracy rate of the model was 95. 83%. The data samples in the remaining 14 years( accounting for about 20% of total number of samples) were used as the test set of the model to test the model,and the test accuracy of the model was 85. 71%. The results showed that the prediction model of number of rainstorm days in summer constructed by C5. 0 algorithm had high accuracy and was easy to explain. Moreover,it is convenient for meteorological staff to use directly. At the same time,this study provides a new idea for short-term climate prediction of number of rainstorm days in summer.
文摘Extremely heavy rainstorm occurred in Beijing on July 21,2012, which was the most serious since 1961. Based on analyzing the precipitation characteristics, formation mechanism of the rainstorm process was analyzed. Results showed that when the precipitation process occurred, it was stable east-high and west-low situation at 500 hPa, and there was a steady stream of water vapor transportation at middle and low layers and strong vertical ascending motion at 700 hPa. The distribution of physical quantity field （relative humidity, vorticity and divergence） showed that they were all benefited to the formation of rainstorm. Then, falling zone of rainstorm and the movement of rain belt, generation, development and weakening of precipitation were analyzed. Finally, according to circulation situation and the distribution of physical quantity at each layer, vertical distribu- tion of physical quantity and distribution of water vapor and jet stream, ＂7 · 21＂ rainstorm model was summarized.
文摘By using the durative rainstorm data in South China during May-early June in 2010,the forecast characteristics of K index and low level jet were analyzed.The results found that K2 had the good indication,advancement and relativity on the intensity and falling zone forecast of regional rainstorm in future 24 h,and the positive relative coefficient reached 0.987.The low level jet also had the same advancement and indication significance on the intensity and influence scope of regional rainstorm in 24 h in the future,and the relative coefficient reached above 0.8.K2 and the low level jet were selected as the main factors,and the basic conceptual model of rainstorm falling zone was established.The model has passed the computer program and realized the business automation.K2 provided the important basis for the forecast of rainstorm intensity and falling zone.
基金This work was supported by the National Natural Science Foundation of China under Grant Nos.40105012,49928504,and 40221503“973”Project under Grant No.G1999032801the Key Innovation Direction Project of the Chinese Academy of Sciences under Grant No.KZCX2208.The authors warmly thank Wu Rongsheng and Wang Yuan of N anjing University for their valuable advice.
文摘The numerical forecasts of mei-yu front rainstorms in China has been an important issue. The intensity and pattern of the frontal rainfall are greatly influenced by the initial fields of the numerical model. The 4-dimensional variational data assimilation technology (4DVAR) can effectively assimilate all kinds of observed data, including rainfall data at the observed stations, so that the initial fields and the precipitation forecast can both be greatly improved. The non-hydrostatic meso-scale model (MM5) and its adjoint model are used to study the development of the mei-yu front rainstorm from 1200 UTC 25 June to 0600 UTC 26 June 1999. By numerical simulation experiments and assimilation experiments, the T106 data and the observed 6-hour rainfall data are assimilated. The influences of many factors, such as the choice of the assimilated variables and the weighting coefficient, on the precipitation forecast results are studied. The numerical results show that 4DVAR is valuable and important to mei-yu front rainfall prediction.
基金financially supported by the National Basic Research Program of China (Grant No. 2009CB421 401)
文摘The authors use numerical model integral products in a third level forecast of synthetically multi-level analog forecast technology.This is one of the strongest points of this study,which also includes the re-ducing mean vacant-forecast rate method,which pos-sesses many advantages with regard to filtering the analog term.Moreover,the similitude degree between samples is assessed using a combination of meteorological elements,which works better than that described using a single element in earlier analog forecast studies.Based on these techniques,the authors apply the model output,air sounding,surface observation and weather map data from 1990 to 2002 to perform an analog experiment of the quasi-stationary front rainstorm.The most important re-sults are as follows:(1) The forecast successful index is 0.36,and was improved after the forecast model was re-vised.(2) The forecast precise rate (0.59) and the lost-forecast rate (0.33) are also better than those of other methods.(3) Based on the model output data,the syn-thetically multilevel analog forecast technology can pro-duce more accurate forecasts of a quasi-stationary front rainstorm.(4) Optimal analog elements reveal that trig-gering mechanisms are located in the lower troposphere while upper level systems are more important in main-taining the phase of the rainstorm.These variables should be first taken into account in operational forecasts of the quasi-stationary front rainstorm.(5) In addition,experi-ments reveal that the position of the key zone is mainly decided by the position of the system causing the heavy rainfall.
