| The northwest vulnerable ecotone(the contiguous area of Shanxi-Gansu-Ningxia-Inner Mongolia)is a specific region which plays the significant role in the ecology,energy supply and social development.Under the global climate change,the frequency,intensity and loss of the meteorological disasters happened in vulnerable ecotone are increased and tend to be on a regular basis.Since the earth science tends to be more phenomenological,symmetry has played an important role in the research on natural disasters,its thoughts and methods will be the new areas of exploration for the research of natural disasters and trend judgments.The paper will make researches and explorations on meteorological disasters' space-time structure and trend,and then come up with some risk management countermeasures about symmetry;the work could enrich symmetry's case studies in the field of natural disasters and perfect the method system of natural disaster research.Based on 40 national meteorological station's date from 1961 to 2013 in northwest vulnerable ecotone,the research will explore the degree of response to the global climate change of vulnerable ecotone and make meteorological disaster identifications.Through the statistical analysis of disasters,it will expand commensurability method by taking symmetry as the breakthrough point,set up some evolution models about space-time symmetry of meteorological disasters combined with GIS spatial analysis method,and explore the main meteorological disasters'space-time symmetry structure in northwest vulnerable ecotone,such as the drought,rainstorm,windstorm disaster and cold damage.Hereunder,it could judge the disaster trend,find the inner mechanism of the meteorological disasters on the basis of symmetry,and perfect the research method system of the natural disaster.Meteorological disaster trend judgment aims to improve the scientific management abilities of disasters.Considered about the result of disaster trend judgment,the study has built a more perfect meteorological disaster risk evaluation index system and has made the risk assessments and risk divisions in northwest vulnerable ecotone.On this basis,the paper will innovatively put forward the symmetry management countermeasures of the meteorological disaster risk in northwest vulnerable ecotone,which gives new research ideas to meteorological disaster risk management.The results of study:i.The response to global climate change of the northwest vulnerable ecotone was prominent which conformed to the trend of the global warming.The trend of global warming was obviously higher than the rate of global warming(0.1 ?/10a)as well as the China's warming rate(0.15 ?/10a).From the spatial distribution,the heating rate of the northwest Tengger sand area in mesoscale partitions and Dongsheng sand area in small scale sites were the fastest.The precipitation(1961-2013)of northwest vulnerable ecotone was decreased in general,and the reduction rate was 3.29 mm/10 a,this was opposite to the country's increasing trend of precipitation in recent 100 years.From spatial distribution and changes,the precipitation reduced gradually from southeast to northwest and the place that has the highest average annual precipitation was in southeast Loess hilly region,while the lowest was in northwest Tengger sand area.From the trend of precipitation change,it gradually transited from reduction to increase along the southeast to northwest.The precipitation of the northeast Maowusu sandy area and Tengger sand area has increased,and the precipitation of the southwest Loess ravine region and southeast loess hilly region has decreased.ii.Under the background of global warming,the drought in northwest vulnerable ecotone has a trend of strengthening gradually,the trend of rainstorm and windstorm disaster have no difference,maybe a little decrease,and the cold damage would weaken dramatically.In the future,the work for meteorological disasters prevention in northwest vulnerable ecotone should focus on the drought,rainstorm and windstorm disaster,and the cold damage prevention can be appropriately reduced.During all meteorological disasters in northwest vulnerable ecotone,in contrast,the symmetry characteristics of drought,rainstorm disasters and cold damage in the historical period were the most notable and the symmetry characteristics of windstorm disaster were not outstanding.After the analysis and trend judgment of large,medium and small scale region's meteorological disasters symmetry characteristics,the result showed that the symmetry characteristics of small and medium scale region was the most obvious and the credibility of the judgment result was the highest,this will be a revelation to study disaster species and spatial scales for symmetry's application in the research of meteorological disasters.Through the space-time symmetry research of the drought,rainstorm,windstorm disaster and cold damage in large,medium,and small scale region of the northwest vulnerable ecotone,in the short term,the study has estimated the trend of all kinds of meteorological disasters' occurrence time and spatial tendency and all the judging results still need to practice and inspect in the future.iii.The research has put the result of disasters trend judgment into risk evaluation index system of the meteorological disaster and has made the risk assessment of all kinds of meteorological disasters in northwest vulnerable ecotone,and the results found that different kinds of meteorological disasters have differnt high disaster risk areas.The areas that have high meteorological disaster risk mainly located in Yulin and Dingbian of the northeast Maowusu sandy area,Luochuan and Xifeng of southeast loess hilly region,and Alxa left banner,Zhongning,and Zhongwei of northwest Tengger sand area,etc.The study plays a guiding role to improve the regional meteorological disaster defense ability of northwest vulnerable ecotone and will provide new thoughts and case study for the application of symmetry regularity in catastrophology and management. |
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