Abstract: The temporal and spatial variation of annual precipitation in Henan province was researched based on the theory of information entropy. The annual precipitation time series at 83 stations from 1960 to 2006 was selected. The estimated information entropy of the annual precipitation time series and the relative value of annual precipitation to its minimum at each station, as well as the estimated information entropy of the annual precipitation’s spatial distribution and the relative value of annual precipitation to its multi-year average in each year,were calculated. Results show that the interannual variation of annual precipitation increases from northwest to southeast and from west to east, and reduces from south to north, but has no obvious regularity from southwest to northeast; while the interannual variation of the relative value of annual precipitation to its minimum increases from southwest to northeast but has no obvious regularity in the other directions. The spatial distribution of annual precipitation was uniform in 1966, 1976, 1999 and 2001 and nonuniform in 2000; the spatial distribution of the relative value of annual precipitation to its multi-year average is uniform in 1986 and nonuniform in 2000.

Key words: information entropy, annual precipitation, temporal and spatial variation, uncertainty