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

Over the past 20 years, several global and terrestrial precipitation c limatologies have been developed. These climatologies have been used e xtensively, for example, to evaluate general circulation model simulat ions of the present-day climate, as input fields in global hydrologica l studies, and to validate satellite precipitation algorithms. If thes e climatologies differ significantly, the results of these application s 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 p recipitation archives-compiled by Eischeid et al., Leemans and Cramer, and Hulme-are compared with the Jaeger and the Legates and Willmott c limatologies to assess precipitation over land areas and the importanc e of the time period of record on long-term averages. Results indicate that seasonal precipitation estimates from the Schutz and Gates clima tology are considerably smaller than either of the other two climatolo gies and its annual average estimate is much smaller than most estimat es of global precipitation made since 1960. Zonally, however, the smal ler estimates are predominantly located in lower latitudes although th e general spatial pattern is similar to that of the other two global c limatologies. Spatial gradients and areas of precipitation maxima are much smaller in the Schutz and Gates climatology, which accounts for i ts lower estimates. Qualitatively, the Jaeger climatology agrees well with that of Legates and Willmott although Legates and Willmott's esti mates are much greater along the Inter Tropical Convergence Zone. Ocea nic 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 observat ion-based climatologies are consistent regardless of the time period o f record and are preferable to climatologies compiled subjectively.