Changes in the Local Growing Season in Eastern China during 1909-2012

Abstract

The lack of long-term daily observations limited the study of changes in thermal growing season in China during the 20th century. Changes in the Local Growing Season (LGS) are analyzed based on a set of homogenized monthly temperature series back to the 19th century at 16 stations in eastern China. The analysis contains three steps: (1) to calculate the LGS indices (including the start and end dates) based on the daily temperature records at the 16 stations for the period 1960-2011; (2) to establish a linear relationship between the LGS indices and monthly temperature records; (3) to reconstruct the long-term LGS index series based on this linear relationship and the long-term monthly temperature records. It is found that, in eastern China, start (end) of LGS exhibits an advancing (a delaying) trend of −1.0 (0.5) days per decade, resulting in a lengthening trend of growing season of 1.5 days per decade, for the period 1909-2012. Changes in LGS indices are not monotonic but with mutidecadal variability. In particular, enhanced LGS-lengthening trends occurred during 1910-1940 and 1965-2012. Especially from 1965 onward, the LGS has been significantly extended by 3.5 days per decade, of which about 35% is contributed from mutidecadal variability.