Correlation Analysis Between Meteorologic Factors And NDVI

Recently, along with social development, the accelerated process of industrialization, human excess exploring and irrationality using natural resource, the environments destroyed, the greenhouse gases' concentration, for example CO₂ are rising, meanwhile, climate change is more obvious. The climate change affects human survival and abidance able development. So, study on the global climate change has become one of hotspot in international science. The purpose of global climate change is to clarify its impacts on terrestrial ecosystem and the reflection of terrestrial ecosystem. Thus, the corresponding strategies can be found out and human can do something to lessen the bad influences furthest. And so, the earth will realize sustainable development. As an important factor of ecology, vegetation is not only enduring the climate change but also has a feedback on climate change positively. It is a sensitive indicator for environment change.The correlation between vegetation and climate exhibition on two aspects: the adaptability of vegetation for climate and the feedback action of vegetation to climate. Climate is the uppermost factor deciding vegetation type and distributing on the earth, while vegetation is the brightest reflection and integration symbol about climate. In plant ecological viewpoint, main vegetation type exhibition vegetable kingdom adapts to main climate type, each climate type or subarea has a corresponding vegetation type. On the other band, different vegetation type affects climate by impact the interchange of substance (water, carbon dioxide, et) and energy (solar radiation, momentum, quantity of heat, et) between vegetation and atmosphere, alterative climate effects vegetation growth by exchanging substance and energy between atmosphere and vegetation, finally will bring on vegetation type change.In china, because of its broad span, complex terrain and remarkable difference of elevation, there are various climate zones and natural sights from doldrums to alp Frigid Zone and from tropical rain forest to drought desert. More over, vegetation index is a reflection of surface vegetation coating and growth status, and through vegetation index it can estimate vegetation coating, growth status and biology capability, et. So, studying the correlation of vegetation index and climate factors has important theory and practice meaning on completely and deeply realizing the apiece elements make up of china natural environment, making clear climate status of china each area, better programming and processing various construction, affording gist of query, application and research for relate departments, such as farming, forest, browse, irrigation, traffic and national defense, and exactitude evaluating and forecasting the affection of global climate alter and affording theory gist for adopting reply policy.In this study, by applying the remote sensing data and time serial analytical method, and by combining geographic information system, remote sensing, statistic tools, analyzed the change rule of NDVI in multi-temporal scale, analyzed the change character of annual or month change of temperature and precipitation, analyzed difference province' the change rule of 12 months multi-annual mean and season multi-annual mean, research the relationship between vegetation and weather factor on annual mean, intra-annual change and inter-annual change. The main results lisit below.Both annual mean and month mean of countrywide NDVI are exhibition stability. Although annual mean NDVI is difference among years, it keeps slowly rise with wave change, While month mean NDVI exhibitions periodicity. Province's NDVI changing trend is similar between two temporal scale, 12 months multi-annual mean and season multi-annual mean, but the NDVI values are contrast difference.On annual mean and month mean two temporal scales, the change trends of countrywide precipitation and temperature are similar. On the 12 months and multi-annual mean scales, the temperature change curves of provinces are closely, while the precipitation change curves are difference distinctly. More over, the season multi-annual mean change curve is complete or not is closely relation to the precipitation of this season or province.Combined the countrywide 303 observatory data and the NDVI data from 1990 to 2001, we can find that, on multi-annual mean level, temperature and precipitation are great effecting on vegetation growth status, and precipitation is effecting more. The total trends are: when precipitation is less than 50mm, NDVI is increasing quickly along with precipitation; when precipitation is more than 50mm, NDVI is calm with little rise. Temperature is plus effect on vegetation growth, but its effect tune is lower than precipitation, and when temperature is under 0℃, NDVI keeps around 03.On the level of during-year's change, most provinces' NDVI has high or middle positive correlation with weather factors of this month. The NDVI OF other provinces which didn't achieve to this strong correlation was also positive correlated to weather factors of this month, only NDVI of few provinces was negative correlated to the weather factors, such as the correlation between NDVI of Yunnan and its monthly mean precipitation, NDVI of Fujian, Jiangxi and monthly mean precipitation. The correlation between NDVI of each province and weather factors of last month was stronger than the correlation between NDVI of each province and weather factors of this month, moreover, the NDVI of most provinces also showed middle correlation with weather factors of last two months. Thus, it can be seem that NDVI has very strong correlation with monthly mean temperatures and monthly precipitation, and shows obviously lag effect.On the level of between-years' change, the main weather factors which effected vegetation's growth was temperature in spring, and its NDVI was middle positive correlated to temperature. The vegetation's growth had a certain lag effect to the precipitation of winter. The precipitation of summer could accelerate the vegetation's growth of arid area, and their correlation was positive, however, the summer NDVI of the other area was negative correlated to precipitation. The summer NDVI mainly showed low or fearfully weak negative correlation, some provinces showed low or middle positive correlation. The vegetation's growth of autumn was positive correlated to temperature, and negative correlated to precipitation, and positive correlated to precipitation of last season, that showed the precipitation of spring and summer could accelerate the vegetation's growth of autumn. In addition, the vegetation's growth of winter was positive correlated to temperature and negative correlated to precipitation. The precipitation of this summer could accelerate the vegetation's growth of winter, but the precipitation of autumn could restrain the vegetation's growth of winter.