Gauge-based monthly analysis of global land precipitation from 1971 to 1994

Monthly gridded fields of global land precipitation have been constructed on 2.5 degrees latitude/longitude grids for a 24-year period from 1971 to 1994 by interpolating gauge observations at over 6000 stations contained in the Global Historical Climatology Network of the Carbon Dioxide Information Center of U.S. Department of Energy and the Climate Anomaly Monitoring System of the Climate Prediction Center of National Oceanic and Atmospheric Administration. Sensitivity tests indicated that this gauge-based analysis has relatively high quality in general and that its quantitative accuracy increases with the gauge network density. Significant value-dependent bias and random error, however, exist in the analysis over grid areas with few gauges. The mean distribution and annual cycle of the 24-year gauge-based analysis showed close agreement with those of several published long-term means, and the inter-annual variations in precipitation associated with the El Nino-Southern Oscillation phenomenon were evident. Despite the ability of this gauge-based analysis to describe large-scale precipitation over global land areas, further efforts are needed to improve the interpolation algorithm, to increase gauge network density, and to combine the gauge analysis with other information sources based on satellite observations, especially over grid areas with poor gauge coverage.