2.3 Trend analysis
Based on the derived EP and SP data, the development modes of the various NH ecosystems in productivity and the snow scenarios in phenology during the study period could be analyzed at the geo-grid level. Specifically, for each of the geo-grids, its individual EP-case- or SP-case-related trend could be characterized by using least-squares linear regression analysis (Harter, 1983). This method can derive the optimal relationship
, (4)
where denotes the serial values of the concerned EP (LEP, AEP, and HEP) or SP (snow-onset and -end SP) case, relates to the related year series, and the fitted coefficient indicates the trend (year-1). Then, we could compare the LEP and HEP ecosystems with the whole ecosystems around the Arctic in terms of the -quantified EP trend.