Drought Characteristics And Forecast Model In Western Semi-Arid Area Of Heilongjiang Province

Heilongjiang Province is a major agricultural province in China, it is also an important commodity grain base.The development of agriculture is constrainted by the weather conditions.on the background of global climate change,the frequency of droughts become more frequent,,drought is the most proround impact,serious and destructive in meteorlogical disasters.thus,study of the basic law of arid climate and blobal warming trends in the context of drought is necessary. By the studying the changes of meteorological drough in accordance with regional characteristics of rational planning and efficient use of water resources,the development of modern water-saving agriculture have important strategic significance on China's food security ecological security and resource security.This paper has studied the city of Qiqihar. The data of Qiqihar City using data provided by the bureau of meteorology,specific research papers reads as follows:(1) The changes in temperature and precipitation trends and interdecadal variations were anylysised by using M-K rank correlation,cumulative filter method,anomaly analysis from the two-year and seasonal time scales. The results show that:Qiqihar City was upward trend in temperature changes in the past 50 years, the rate of changes tend was 0.486℃/10a,each season starting from 70 years to present.There was various degrees of upward trend,,but the most signeficant warming-up was in winter,followed by spring;Annual precipitation in the downward trend,trends was not obvious,spring and winter precipitation was an increase in the overall trend,and the winter increase in precipitation rate is higher than that in spring, autumn rainfall is decreasing trend.Terms of the changes from the trend to the next years,summer and autumn rainfall will continue to decrease,while the spring and winter precipitation will continue to increase.(2)With the standard deviation method,precipitation was diveded into five grades:logging, partial waterlogging,normal,partial drought and drought.The city's scale and frequency of drought and flood analysis table were listed, droughts and changes in time and space characteristics were obtained.In time, drought and flood has a freqrency alternating with the continuity and universal character.In all these years,the year of drought and flood occurred far more than anormal year,indicating Qiqihar City is a disaster-prone area,and the frequency of drought occurrence is higher than that floods.In space,.statistical tables from the drought and flood frequency analysis with regional characteristics shows that:Fuyu county in all counties in either drought or flood,the probability of occurrence were the largest one, followed by Yian and Longjiang County,Baiquan,Tailai County,Kedong,Keshan,Nehe City,and Gannan County is relatively small,but the probability of drought minimum 31.4%,the probability of flooding is also 50 percent more than the minimum,Against the severity of desasters,then presents a desaster countermeasures.(3)Markov chain is both the state and time-descrete Markov process,referred to as "Markov chain".Precipitation.It is a random sequence,in line with Markov property,can be applied to the weighted Markov model.Precipitation in the state of Qiqihar City in 2009 to predict the results of partial flood year.Weighted Markov model overcomes the shortcoming of the traditional Markov,reaching the purpose of fully and rationally use of information,but also predicts that a future time interval of precipitation is a change,rather than a specific value, this way,the projected scope of the its predicted reliability can be increased accordingly.(4)Application of genetic algorithm based on projection pursuit autoregressive model predicted precipitation,results showed that PPAR models to predict precipitation is feasible and effective. PPAR model calculation is simple,applicable to overcome the shortcomings of the computational complexity and programming difficulties of traditional projection pursuit method. Projection pursuit method is conducive to the promotion and application providing a new approach in order to deal with linear time series prediction worth exploring.