Annual precipitation fields secular variation over global land areas for 1948—2000

摘要

The secular variation over the global land annual precipitation (GLAP) fields for 1948—2000 is investigated. Evidence suggests that the GLAP abruptly reduced around 1978 and experienced a decrease of 0.54 mm/a, on average. Fuzzy clustering is used to group the annual precipitation over commonly-used 36 latitudes belts into six belts for examining its secular variation. The results show that, except northern high-latitudes (60°—90°N) where it is slightly increased, the precipitation is decreased, especially in 35 °N—35°S, and the diminution is the maximum of 0.98 mm/a at tropics. Moreover, identification of 1948—2000 flood/drought years on a global basis is made, showing noticeable interdecadal variations. During the years of warm (cold) events the precipitation decreases (increases) by 15.4 mm (14.4 mm) per year, on average. It can be assumed that global warming and frequent ENSO occurrences from the end of the 1970s maybe serve as the root cause of the diminution.