GLOBAL AND TERRESTRIAL PRECIPITATION - A COMPARATIVE-ASSESSMENT OF EXISTING CLIMATOLOGIES

Over the past 20 years, several global and terrestrial precipitation climatologies have been developed. These climatologies have been used extensively, for example, to evaluate general circulation model simulations of the present-day climate, as input fields in global hydrological studies, and to validate satellite precipitation algorithms. If these climatologies differ significantly, the results of these applications may be affected adversely. In this paper, three global precipitation climatologies-developed by Schutz and Gates, Jaeger, and Legates and Willmott-are examined comparatively. Additionally, three terrestrial precipitation archives-compiled by Eischeid et al., Leemans and Cramer, and Hulme-are compared with the Jaeger and the Legates and Willmott climatologies to assess precipitation over land areas and the importance of the time period of record on long-term averages. Results indicate that seasonal precipitation estimates from the Schutz and Gates climatology are considerably smaller than either of the other two climatologies and its annual average estimate is much smaller than most estimates of global precipitation made since 1960. Zonally, however, the smaller estimates are predominantly located in lower latitudes although the general spatial pattern is similar to that of the other two global climatologies. Spatial gradients and areas of precipitation maxima are much smaller in the Schutz and Gates climatology, which accounts for its lower estimates. Qualitatively, the Jaeger climatology agrees well with that of Legates and Willmott although Legates and Willmott's estimates are much greater along the Inter Tropical Convergence Zone. Oceanic estimates vary considerably which underscores the uncertainties in estimating oceanic precipitation. Over land, the Legates and Willmott climatology compares favourably with the observation-based estimates from the terrestrial archives, leading to the conclusion that observation-based climatologies are consistent regardless of the time period of record and are preferable to climatologies compiled subjectively.