Global Land Surface Extremes of Precipitation: Data Limitations and Trends

The lack of ready availability of daily precipitation data is a barrier to global analyses of long-term trends in extreme precipitation over land areas. Good availability of station data in the readily accessible Global Historical Climatological Network dataset is concentrated in Northern Hemisphere (NH) mid and high latitudes. The NH subtropics, the tropics, and Southern Hemisphere land areas are not well represented in this dataset. Our analysis of global trends for 1951–2014 spans a transition from slowly increasing greenhouse gas concentrations in the 1950s to accelerating increases after the 1960s. We have examined common metrics as well as ones that are more extreme than what is typically studied and thus are more relevant to engineering applications. The area of increasing trends is approximately 1.5–2 times the area of decreasing trends for all of the metrics. These results show an increase at mid and high latitudes with a high level of confidence. Some areas with predominantly downward trends include western North America, the east and west coasts of Australia, and the Mediterranean Sea region. Recent studies on extreme precipitation have added to our knowledge of historical trends for selected regions. A number of studies for regions in China indicate a mix of upward and downward trends, but dominated by upward trends. Trends for India are not consistent among studies and thus no clear statement can be made. Studies for Africa are of limited use because the periods of analysis are shorter (due to lack of data availability) and thus cannot be directly compared with other regions. Overall, these recent regional studies do not cover sufficient area to make any general statements for zonal belts outside the NH mid and high latitudes.