ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 42 Issue 12 > 2016,42(12):1456-1464. DOI:10.7519/j.issn.1000-0526.2016.12.003 Prev Next
The ECMWF Model Precipitation Systematic Error in the East of Southwest China Based on the Contiguous Rain Area Method for Spatial Forecast Verification
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Abstract:
The contiguous rain area (CRA) is an objectoriented verification procedure. By setting a threshold for precipitation, the CRA is identified and isolated, and the forecast error of the rain area can be analyzed. This method can avoid the “double penalty” effect of traditional score method. The horizontal displacement is determined by translating the forecast rain field to the observation. This allows a decomposition of total error into components due to the rain location, amount and pattern. 119 CRAs from May to September in 2011-2014 over the east of Southwest China were found by using the CRA technique. Their location and intensity errors of the forecast by ECMWF model in 36 h were analyzed by the CRA verification method in this paper. Then these cases were classified into three types according to the weather systems, i.e., the low vortex and shear line over the east of Southwest China (the first type), the shear line located over Jianghuai Basin and the east of Southwest China (the second type), and the southerly wind type (the third type), respectively. The systematical error of each type was presented. The results showed that the pattern error for all CRAs is the greatest about 60% of the total error, then is the location error, about 30%, and the amount error is the least, about 10%. The average location error is 0.7° westward to observation, and the meridional displacement error is not clear. The mesoβscale rain area may fail to be forecasted by the model. However the horizontal scale larger than mesoβscale rain events would be overforecasted to have more rain area and total rainfall, but weaker intensity. The intensity error is similar to the first and the second types, in which the rain areas are overforecasted and the average rain intensity and maximum rainfall are underforecasted. However, the intensity is underforecasted or the event is missed for the third type. For the location error, it is westward for the first type, northwestward for the second type, and southwestward for the third type.
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