Trends of regional precipitation and their control mechanisms during the 1979–2013 global warming

Abstract:

Trends in precipitation are critical to water resources. Considerable uncertainty remains concerning trends of regional precipitation in response to global warming and their controlling mechanism(s). Here we use an inter-annual difference method to derive trends of regional precipitation from data of Global Precipitation Climatology Project (GPCP) and Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis in the near-global domain of 60°S–60°N during a major global warming period of 1979–2013. We find that trends of regional annual precipitation are primarily driven by changes in the top 30 % heavy precipitation which in turn are controlled by changes in precipitable water in response to global warming, i.e. by thermodynamic processes. Significant drying trends are found in most of the US and eastern Canada, the Middle East, and eastern South America, while significant increases in precipitation occur in northern Australia, southern Africa, western India and western China. In addition, as the climate warms there are extensive enhancements and expansions of the three major tropical precipitation centers, namely the Maritime Continent (MC), Central America, and tropical Africa, leading to a significant strengthening of the global hydrological cycle. However, there are significant discrepancies between observed trends derived from GPCP and those from a typical climate model (MPI ECHAM5) during the period 1979–2013, raising a serious concern regarding the capability of climate models in their projections of trends of regional precipitation in response to global warming.