Change of mean annual precipitation

The change of the mean annual precipitation is calculated based on the land surface precipitation climatology from rain gauges of the reference periods 1961 to 1990 and 1981 to 2010. Note that the number of rain gauge stations is highest for the 1980s and 1990s, with up to 50 000 stations, while this number decreases below 30 000 until the year of 2010 Source: GPCC