Comparison of the new LTDR AVHRR reflectance with the GIMMS AVHRR

8 9 The GIMMS Advanced Very High Resolution Radiometer (AVHRR) NDVI dataset has nearly 10 three decades of observations and is the most widely used vegetation index dataset. In this 11 short communication, we compare AVHRR normalized difference vegetation index (NDVI) 12 data from the GIMMS group with NDVI created from the Long Term Data Record (LTDR) 13 daily reflectance. The two datasets have substantially different processing characteristics, 14 with the LTDR offering daily channel data, higher resolution and more complete 15 atmospheric correction than the reflectance from which the GIMMS data were derived, but 16 the data ends in 1999. Understanding and characterizing the impact of the differences 17 between the GIMMS and LTDR datasets is a first step in being able to exploit the temporal 18 and spatial resolutions offered by the new LTDR AVHRR dataset. We found that although 19 there are significant differences between the datasets, they are broadly comparable during 20 the 1981-1999 period. The LTDR AVHRR dataset will provide a solid foundation for future 21 AVHRR datasets once it has been extended through to the present. 22 23 Manuscript