青藏高原冬季NDVI与西南地区夏季气温的滞后关系

该文利用EOF分解得到的1982—2001年西南地区夏季平均、最高和最低气温的时空特征显示, 西南地区夏季平均、最高气温的时空变化具有很好的一致性, 尤其是川渝地区20世纪80年代为气温负距平, 90年代开始有明显升温。利用GIMMS NDVI和西南4省市96个台站的气温资料进行了相关分析、合成分析以及SVD分析, 得到前期冬季青藏高原植被影响该区夏季气温的滞后关系以及影响较大的区域。结果表明:西南地区夏季平均气温、最高气温对青藏高原冬季植被变化较敏感, 其中青藏高原西部NDVI与西南地区夏季气温的相关强于东部; 青藏高原NDVI异常偏高对应西南地区夏季气温偏高, 其中最高气温升高较明显, 增温最大值出现在7月, 位于西南地区北部; 青藏高原冬季植被变化与西南地区平均气温、最高气温和最低气温的最佳耦合模态中影响程度及关键区域略有差异, 青藏高原冬季NDVI与夏季平均气温关系最密切, 其中青藏高原东北大部分地区和南部 (包括拉萨及林芝东部地区) 的影响最大, 气温对前期青藏高原NDVI变化反应的敏感区主要位于四川盆地及其附近地区。

The Lag Relationship Between Winter NDVI over Tibetan Plateau and Temperature of the Southwest China

Many studies show the importance of vegetation to climate. Southwest China neighbors to Tibetan Plateau, by which climate of this region is influenced by its own system. Therefore, taking account of both factors it is considered that climate of Southwest China is affected by vegetation over Tibetan Plateau to some extent. The lag relationships between NDVI over Tibetan Plateau and temperature of Southwest China are discussed by using statistical methods. Empirical orthogonal function (EOF) analysis is made first to describe temporal and spacial characteristics of mean temperature, highest temperature and lowest temperature in summer over Southwest China during the period of 1982—2001. The results show that there is a coincidence between mean temperature and highest temperature, especially Sichuan and Chongqing are in a cool period during 1980s and getting warm in 1990s. Based on the monthly Normalized Difference Vegetation Index (NDVI) data that is made by GIMMS (Global Inventory Modeling and Mapping Studies) workgroup and the monthly mean air temperature, maximum air temperature and minimum air temperature data of 96 stations in Southwest China, the relationships between NDVI over Tibetan Plateau and temperature of Southwest China and key regions are analyzed by applying correlation, composite and singular value decomposition (SVD). The results show that mean temperature and highest temperature are more sensitive to vegetation change, and the correlation between temperature and preceding NDVI has a significant difference between tow parts of the Plateau, vegetation over the West Plateau shows a stronger influence on temperatures than the east part. Compared with the years of abnormally low NDVI, abnormally high NDVI in winter over the Plateau corresponds to a warming in Southwest China in summer, highest temperature increases most obviously, the maximum increase occurs in July in north of Southwest China. The best coupled patterns of NDVI and tem peratures are showed respectively, the extent of vegetation's impact on temperatures and key regions are distinguished. The strongest correlation is found between the Plateau NDVI of winter and mean temperature of summer; mean temperature is driven by vegetation in northeast part of the Plateau, Lhasa and Linzhi predominately. For highest temperature the area of remarkable correlation is located in west of the Plateau and the large area along the north edge of the Plateau, and for the lowest temperature is the belt region along the north edge of the Plateau. The regions sensitive to the change of winter NDVI are mainly located in Sichuan Basin and the vicinity of it.