Study of the vegetation index-meteorological factor correlation adjusted by accumulated growing degree days

In previous studies, the correlation between the vegetation index and meteorological factors were investigated with in intervals defined by the day-of-year. Compared with the day-of-year, the accumulated growing degree days (AGDD) more effectively reflect vegetation growing stage, which serves as important references in agricultural management and disaster prediction. From this end, it is also worth to investigate vegetation-meteorological factor correlation within intervals defined by the AGDD. In this paper, pixel-wise VCI-meteorological factor (i.e. precipitation and temperature) correlation was analyzed in grass/pasture land by different intervals adjusted by the AGDD. According to results, variances of VCI-meteorological factor correlation were unveiled across different intervals. Summarily, the temperature serves as the dominant factor on VCI dynamics before the heating accumulation necessary for grass growing is achieved. Within these intervals, the precipitation is weakly correlated with the VCI. As excessive heating is received after necessary heating condition is met, the precipitation replaces the temperature as the controlling factor and shows increasingly positive correlation with the VCI. Within the same intervals, VCI-temperature correlation coefficient decreases to negative level. The work in this paper is helpful to better understand intra-annual variances of VCI-meteorological factor correlation. Results from this paper will also serve as the reference for agricultural practices and management.