Climate Comfortable Index Changes And Its Response To Ecological Environment In The Weihe River Basin

Climate change has a significant impact on human society, which is closely related toecology, environment, water, energy sources and sustainable development, therefore climatechange plays an extremely important role in the climate comfort index. Wei River is thebiggest tributary of Yellow River. It rises in North part of Qinling Mountain and the LoessPlateau, belonging to the continental monsoon climate zone and covering semi-humid andsemi-arid areas. In the northern area of WeiHe River basin soil erosion is severe andecosystem is fragile. Weihe Rive basin has a long history of agriculture development and isthe birthplace of Chinese national civilization. During the Chinese history process andmodern time this region has played an important role and considered as key area in term ofeconomy development and ecological environment care. Therefore, it has a certain practicalsignificance to study the climate index changes due to climate change, and to evaluate therelationship among climate, regional environment and climate index.Based on temperature, wind speed, relative humidity and NDVI image data in terms ofthe tendency analysis, change point, spatial interpolation, accumulated variance analysis,Mann-Kendall method, and statistics analysis has been systematically analyzed by differentmethods. According to meteorological and NDVI data in Wuqi station during1998－2008, toanalyze the relation of climate change, Vegetation cover changes and climate comfortableindex. The main results have been showed:(1)The annual temperature in southeast is higher than the annual temperature innorthwest, annual temperature, annual max temperature, and annual min temperature showeda significant increasing trend during the past50a,rate of annual temperature is0.23℃/10a, itis pass the95%the confidence level interval, and the rate is higher than nationwide, but islower than northwest.The temperature in1990s increased faster than the other decade. Thechange point occurs during late1980s to early1990s, especially in1993and1995. It is thesame trend to the change of northwest.The annual relative humidity and wind speed of most station are showed a significantdecreased trend, the speed change is0.07. The wind speed has significant decreased in1960s, the peed change is0.071. and both meteorological factor pass the95%the confidence levelinterval.(2)All the climate comfortable index has changed in the Weihe river basin, and hasincreased except index1(cold days) which changed most significant during the past50a, andthe descent speed is5.5d/10a. Index4～5(comfortable days) which are showed a significantraised trend,index1and4～5have both passed95%the confidence level interval.Meanwhile the cold days increased from east to west, and from south to north, the highelevation region has more cold days and less comfortable days.(3) Vegetation NDVI has an increased trend during the past10a, the lowest vegetationcover in1999, but highest in2003. Meanwhile the low vegetation cover area is decreased;high vegetation cover area is increased. It is negetive correlate between vegetation cover andclimate comfortable days, higher vegetation cover to less comfortable days.(4) Comparing with the whole Weihe river basin, the annual temperature is decreased by0.655℃/10a in Wuqi County, which is on the contrary to the whole basin, but have not passed95%the confidence level interval. The decent speed is faster in Wuqi County than raisedspeed in whole basin. The change trend of relative humidity and wind speed in Wuqi is thesame as the whole basin, but the speed of change is slower. The speed of the vegetationcover is faster than the vegetation cover in whole basin. High vegetation coverage hasraised, but low vegetation coverage has descended. It is positive correlate between vegetationcover and climate comfortable days, higher vegetation cover to more comfortable days, and itis negetive correlate between vegetation cover and cold days.