| Binzhou city is located in the lower reaches of the Yellow River,Lubei Plain.It's the hinterland of the Yellow River Delta and on the south of Bohai Bay,also known as the “North Gate” of Shandong Province.Hail weather is one of the most destructive weathers over there.Hail weather has a strong locality and it is difficult to predict,often causing significant social and economic losses.The previous study emphasizing on hail in Binzhou is limited to single hail example conventional weather analysis and radar detection data applications.Analysis of the climate characteristics of hail,weather classification and other work have not carried out,and there is no hail forecast method set especially objective prediction method.Therefore,in order to further strengthen the recognition of local hail weather characteristics and causes and improve the accuracy of hail weather forecast and give earlier warning,so as to achieve better service and defense effect,this paper carried out the research.Based on the data of hail process in Binzhou City from 2001 to 2011,the data of high and low level,as well as physical field were collected and analyzed.The temporal and spatial distribution characteristics of hail,the characteristics of weather scale and the general physical characteristics were studied,the representative physical quantity indexes were selected by using weather and statistical methods,the hail potential physical quantity index forecasting method in Binzhou Area is established on the basis of weather typing.The main results are as follows:(1)Hail weather in Binzhou has unique temporal and spatial distribution characteristics.From 2001 to 2011,the number of hail days in Binzhou City was 96 days,the average annual distribution was 8.7 days,and the annual distribution showed a decreasing trend.Every year,the hail appeared in April to October,and was concentrated from May to July.Among them,the number of hail days in June was the highest,and the number of hail in July was the second.The earliest date of hail was April 7,the latest date was October 14.Hail were most from 14:00pm to 2:00am the next day,followed by 8:00am to 2:00pm,and 2:00am to 8:00am with least.From the spatial distribution of hail,it has a strong local nature,the hail which only occurred in one country accounted for 44.79%,the hail which occurred in 2 countries accounted for 26.04%,the hail which occurred in 3 countries accounted for 15.63%,and the hail which occurred in more than 4 countries accounted for only 13.54%.(2)Through statistical analysis,most of the hail process has caused varying degrees of meteorological disaster,and the disaster losses were mostly more than 1 million yuan.Among them,there were 6 hail days which lost less than 1 million yuan,25 hail days which lost between 1 million to 10 million yuan,21 hail days which loss between 10 million to 100 million yuan,and 3 hail days which lost more than 100 million yuan.Generally,hail with diameter above 1cm and duration of above 2 minutes might cause a disaster,and most will be associated with strong winds,heavy rain and other disasters.The largest observed diameter of hail was 6 cm during the eleven years in Binzhou.(3)According to the weather situation of hail in Binzhou,four major types of hail weather were summed up:(1)low vortex type,(2)low-level trough type,(3)transverse trough type,(4)north-west airflow type.In addition,under the influence of the shear line,the edge of the high-pressure ridge and the south-west airflow,there would be hail weather occasionally,but small range of falling hail.Among them,(1)the low vortex type of hail indicated there has been accompanied by a cold vortex activity in the range of 37 ~ 45?N and 105 ~ 135?E at 500 hPa.Under its influence,Binzhou area appeared hail.According to the vortex centrel distribution,the first and second key areas of the low vortex hail were given.(2)The low trough type of hail referred to in the range of 35 ~ 45?N,105 ~ 120? E at 500 hPa,there were low-level troughs moved from west to east to affect Binzhou,with low-level trough,shear line,inverted trough or other low-value system in low level to match.Almost there was a strong warm ridge at 850 hPa in this type every time.Most of the low-level trough hail occurred during the day,afternoon to evening,and rarely occurred at night.The low-level trough type of hail was also divided into four types: the front trough type,the stepped trough type,,the deeper low-level trough type,and the type of trough associated with low latitude system.In the front trough type and stepped trough type,mostly caused hail in more than 2 countries.The other two types mostly caused hail in only 1 to 2 counties.(3)The transverse trough type hail meant there was a high-pressure ridge near the Lake Baikal(sometimes weak)at 500 hPa,existed low vortex or high-altitude though in China's northeastern or eastern Russia,and existed transverse though in the southeastern part of Inner Mongolia to the north China.Under the guidance of the north-west airflow,the transverse through with a strong cold air turned the south swing near the north China and affected the occurrence of hail in Binzhou area where had a warm surface.The effect of transverse though type of hail was wide and destructive,most of this type could cause hail in more than 2 counties.(4)The north-west airflow type of hail performed two circulation situation at 500hPa: the first was that there was a high-pressure ridge near the Lake Baikal,existed low vortex or high-altitude though in China's north-eastern or eastern Russia,and existed strong north-west airflow before the ridge from Mongolia to Shandong;The second was the high pressure ridge near the Baikal Lake,but was not obvious.It's consistent north-west airflow from Xinjiang Province to Shandong Province,low-value system strengthened into the north-west airflow near to or on the east of Baikal Lake.The wind speed was larger above 700 hPa,and a stable warm ridge was showed in the 850 hPa.There were wind shear or the strengthening southwest wind,constituting a strong vertical wind shear and the stratification instability of cold on the warm situation with high altitude system,which caused hail in Binzhou.(4)Based on the statistical method,the physical quantity indexes such as K index(K)and Showalter index(SI)were analyzed by the coefficient of variation,scatter plot,box diagram and histogram.The 8 kinds of physical quantity indexes of the height of 0? layer at 0? and 20? and the thickness between them,K index(K),total index(TT),storm severity Index(SSI),strong weather threat index(SWEAT)were obtained,they had a high degree of concentration and stability.The physical characteristics of the different indicators were statistically analyzed from the different categories,such as disaster,regional size,diameter,time of occurrence,influencing system.The single-index fitting method was used to determine the combination of three types of hail forecast physical indicators in June,July to August,as well as other months,and established potential objective prediction method of hail in Binzhou Area.(5)Based on the objective forecasting method of hail potential,the hail potential forecasting system in Binzhou was developed by using PHP,HTML5,AJAX,MySQL and other technology.The system combines forecasting methods with modern information technology and realizes the query of the research results,realizes the browsing of the historical hail process,and realizes the intuitive display of the data input to the system result,provides new technical support for the forecast,service and defense of the hail in Binzhou City. |
PDF Full Text Request