The objective analysis of daily rainfall by distance weighting schemes on a Mesoscale grid

Abstract

The authors studied the error of spatial interpolation in the context of a climatic data gridding project (CLI-GRID). Four objective analysis (QA) techniques were implemented: the empirical techniques of Barnes, Cressman and Shepard, and a Gandin-based statistical technique. These were applied to the interpolation of irregularly distributed daily rainfall data. Spatial resolution of the interpolated arrays was 0.05 degree of latitude by 0.05 degree of longitude.In this experiment, radar rainfall patterns served as reference data for evaluations of O A techniques. Each reference pattern was sampled at the irregularly spaced locations of a climatic rain-gauge network. The sampled data were then input to one of the four OA techniques. The resulting analysis was subtracted from the corresponding reference pattern. Absolute values of the differences were recorded. This sampling-to-difference cycle was repeated with 63 reference patterns. Every map of absolute differences was summed. The resulting map of total errors was normalized by the sum of the reference patterns. Average bias, average RMS error and averages of the ratios of the standard deviations were also computed.All four OA techniques were evaluated separately. The authors recognized that totally unbiased intercomparisons were not possible because of the range in execution parameters for each O A technique. Reasonable efforts were made to minimize subjectivity in the setting of parameters. For application to the specific project grid, the statistical optimal interpolation technique displayed the lowest RMS errors. This technique and Shepard OA, were found more suitable than the other two techniques studied. Statistical and Barnes OA displayed zero average bias and would be useful for areal average computations. The Cressman OA was judged least suitable for interpolation of daily rainfall.An application of the two-dimensional error maps to network analysis was demonstrated by plotting the relationship between interpolation errors and distance (D) from the closest station. Error increased as D 1/2 . It was also verified that error and station density were inversely related. RÉSUMÉ Les auteurs ont étudié V erreur d'interpolation spatiale dans le contexte a" un projet pour le quadrillage de données climatiques « CLI-CRID» . On a implanté quatre techniques d'analyse objective « AO » : les techniques empiriques de Barnes, de Cressman et de Shepard, ainsi qu'une technique statistique du même type que celle de Gandin. On a utilisé celles-ci pour effectuer l'interpolation de données de hauteurs des précipitations espacées irrégulièrement. La résolution spatiale des matrices d'interpolation était de 0,05 degré de latitude par 0,05 degré de longitude. Dans cette expérience, on a utilisé des patrons radar, en tant que données de référence, pour l'évaluation de techniques d'OA. On a échantilloné chaque patron aux positions irrégulières des stations d'un réseau de pluviomètres. On a ensuite fourni ces données échantillonées à l'une des quatres techniques d'AO. On a soustra...

A description of the global land-surface precipitation data products of the Global Precipitation Climatology Centre with sample applications including centennial (trend) analysis from 1901–present

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A 50‐year high‐resolution atmospheric reanalysis over France with the Safran system

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Interannual and seasonal variability of modelled soil moisture in Oklahoma

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