Impact of Pathfinder AVHRR Data Error on the Large-scale NDVI/Temperature Coupling
资料误差对大尺度NDVI-气温关系的影响

The pathfinder AVHRR NDVI data are widely used for analyzing the response of vegetation condition to climate change. However, the Pathfinder NDVI data sets contain a lot of random errors due to various factors such as cloud, aerosols, instrumental interruption and changes and so on. To what extent these errors can influence the results of NDVI/climate connections? In the present work,the authors analyzed the impacts of NDVI errors on NDVI/temperature coupling in spring, by using singular value composition analysis technique. Four kinds of errors are tested, including the continuous, discontinuous and volcanic errors, and the error trends as well. Results show that when the errors are less than half the original NDVI standard deviation the SVD spatial modes and temporal changes are stable and independent of the error. However, if the error gets larger, the results would be distorted apparently. Comparison experiments conducted in the present study suggest that the upper limit of potential errors for reasonable results is about 0 5 standard deviations of the original NDVI series. Actual errors are likely to be within this limit, thus the results from the original data are acceptable. In addition, the methods applied in the study can be applied to the similar research to test the significance and robustness of the results in case of unknowing how large the error is.