海河流域NDVI对气候变化的响应研究

Responses of NDVI to climate change in the Hai Basin

以海河流域为研究区,利用8km分辨率AVHRR/NDVI数据和气象资料,逐像元对1981—2000年时段的流域NDVI值、年降水量和年均气温的变化率进行分析,计算了NDVI和年降水量、年均气温的相关关系。结果表明,1981—2000年时段内,海河流域年降水量变化总体呈现北部和南部增加,中部减少的趋势,其变化范围在-80mm/10a—80mm/10a之间。全流域气温均呈上升趋势,其中五台山地区上升最显著,达2℃/10a左右。NDVI在京、津等大城市周围显著减小,变化率达-0.8/10a,在流域东南部平原及燕山部分山区增加趋势明显,达到0.8/10a左右。NDVI与降水、气温的相关关系空间差异明显。在海河流域冷湿区,如滦河上游草原区和五台山地区,植被指数对降水变化不敏感,与气温呈显著正相关关系。太行山南端暖湿气候环境中,降水增多影响植被生长。海河流域东部沿海平原及燕山北部等干燥环境下,NDVI与降水呈正相关关系,与气温呈显著负相关性,而在山前平原农灌区,作物对气候因子变化响应不敏感。

In this study,based on the RS and GIS systems,AVHRR/NDVI data of 8 km resolution and meteorological data were used to analyze NDVI,annual precipitation,and temperature change rates by pixel from 1981 to 2000.In addition,the correlation between NDVI,annual rainfall,and annual average air temperature were calculated.The results showed that annual precipitation increased in the northern and southern areas of the Hai Basin from 1981 to 2000 while declining in the central area,with a range of-80 to 80 mm/10 a（＇a＇ represents a year）.As basin-wide temperatures increased,the Wutai Mountains area had the most significant increase,up to about 2℃/10 a.The NDVI reduced significantly in Beijing,Tianjin and other large adjacent cities,with a change rate of about-0.8 NDVI/10 a while increasing in the southeast part of the plains of the Hai Basin and the Yanshan Mountains,at about 0.8 NDVI/10 a.The correlation between NDVI,precipitation,and air temperature had significant spatial variation.In the cold and wet areas of the Hai Basin,such as the grasslands in the upstream areas of the Luanhe River and the area of the Wutai Mountains,the vegetation index is not sensitive to precipitation while it is correlated positively with the air temperature.In the warm and wet climate areas,such as the south end of the Taihang Mountains,the precipitation affected vegetation growth when it increased.In dry conditions,such as the eastern coastal plain and north of the Yanshan Mountains of the Hai Basin,NDVI significantly was correlated positively with precipitation and negatively with air temperature.In the irrigated agriculture areas of the piedmont plain,crop growth was not sensitive to climate changes.