West-east contrast of phenology and climate in northern Asia revealed using a remotely sensed vegetation index

摘要: The phenology of the vegetation covering north Asia (mainly Siberia) and its spatial characterstics were investigated using remotely sensed normalized difference index (NDVI) data. analysis used weekly averaged NDVI over 5 years (1987-1991) second-generation global dataset (0.144�� 0.144� resolution). In seasonal cycle, three phenological events defined for each pixel: green-up week (NDVI exceeds 0.2), maxi- mum week, senescence drops below 0.2). Generally there was a west-early/east-late gradient in Asia. zonal transect between 45� 50�N, timing green-up, maximum, near 60�E (Kazakh) about 3.4, 8.7, 13.4 weeks earlier than 110�E (Mongolia) respectively. It has been suggested that Kazakh only flourishes during short period when water from snow melt is available late spring to early summer. Mongolia, abundant vegetation, even midsummer, because precipitation. 50-60�N transect, 40�E 3.8 3.9 115�E, As senescence, no clear west-east trend. This west-to-east related cumula- tive temperature (over 0 �C). Weeks which cumalative exceeded 40 �C 140 had similar distribution maximum NDVI.