Analysis of phenological change patterns using 1982-2000 Advanced Very High Resolution Radiometer (AVHRR) data

Using the National Oceanic & Atmospheric Administration (NOAA) National Aeronautics & Space Administration (NASA) Pathfinder Land dataset (PAL data) from 1982-2000, vegetation phenology (onset, peak and offset) was defined and analysed with climate data. In areas of precipitation-dependent phenology such as Central Africa, it was found that Normalized Difference Vegetation Index (NDVI) is affected approximately 20-40 days after the occurrence of precipitation, depending on land cover types. In areas of temperature-dependent phenology such as Siberia, the relationship of phenology and latitude/elevation was investigated. Using temporal NDVI data of 1982-2000, changes in seasonal NDVI pattern were classified into 11 classes and mapped in the Northern Hemisphere. From this analysis, increasing trends of the annual sum of NDVI were found in Siberia, NE Europe and the northern part of North America where good correspondence with the increasing trend of air temperature was recognized. In contrast, some areas such as the east of the Aral Sea showed a decreasing trend of the annual sum of NDVI. It was found that, in the Northern Hemisphere, the area with increasing trend of the annual sum of NDVI is approximately 12 times larger than the area with the decreasing trend. Also, it was found that areas of increasing/decreasing trend of the annual sum of NDVI correspond roughly to areas with increasing/decreasing trend of air temperature from 1982 to 1995.