A phase analysis of season on the earth surface using GVIP data

October is the peak of fall in the middle latitude whereas August is the beginning of the season in the northern polar region. In the northern polar region, the peak of the infrared reflectance arrives at the beginning of August and it marks the onset of sleet. Thus, fall starts earlier in the northern polar region. However, the emergence of red-leaf is what is actually used as an index of fall. Reddening of leaves progresses from the north to the south. When fall is defined as the period in which leaf blossom is at its peak, then the period could be used to analyze the time of fall in the region. On the contrary, fall dose not occur in the tropical region. However, it is known that the tropics vegetation reaches full blossom a few weeks after the end of the rainy season. This time could be defined as being equivalent to fall. Thus, our objective is to determine the time of fall all over the world by making a phase analysis of a time series of NOAA/AVHRR data. The first approach makes use of a method, which considers the date on which the channel 2 data records the peak value to be the date of fall. A global view of fall obtained by this method is presented. Progress of fall is indicated correctly in the eastern part of the Asian continent and the North American continent. The equivalent of fall in West Africa is discussed as representative of the season in the tropical region.