Where have all the showers gone? Regional declines in light precipitation events in China, 1960-2000

摘要

China has seen a decline in recorded precipitation events over 1960-2000. We find that this decline is mainly accounted for by the decrease of light precipitation events, those with intensities of 0.1-0.3 mm/day. The annual number of light precipitation events drops off remarkably around 1978 and decreases rapidly until 1985. Trace precipitation events (precipitation noted but measuring < 0.1 mm/day) decrease abruptly from 1982 through the end of the period. Meanwhile, the annual frequency of precipitation events with intensities above 0.3 mm/day shows almost no change for the same period. The analysis uses daily data from 272 stations distributed across China. We note regional and seasonal differences in the rates of change of different intensities of precipitation events. With almost no change in the frequency of precipitation events of 0.4-0.6 and 0.7-0.9 mm/day during the same period, it is difficult to attribute the abrupt decreases to inhomogeneities of the precipitation data. The temporal pattern of light precipitation events is similar to those observed for solar irradiance and total cloud cover, suggesting that there may be some connections between these climatic variables. Declines in solar irradiance and total cloud cover along with increased aerosol loading may have contributed to the abrupt decrease of these light precipitation events. However, light and trace precipitation events display different spatial and temporal patterns of change, complicating this explanation.