Analysis and verification of reconstructed historical extreme precipitation events in an hourly resolution
Abstrakt
Our knowledge of the course of extreme precipitation events (EPEs) based on both radar and automatic rain gauge measurements is limited to the last two decades; historical events can usually be characterized only by daily precipitation totals. This paper applies a newly developed method that enables the reconstruction of the subdaily course of historical precipitation events using precipitation simulations by the numerical weather prediction (NWP) model COSMO.
The method is based on the adjustment of 24-h model precipitation sums by daily rain gauge measurements and on the subsequent correction of 10-min precipitation intensities simulated by the model. The method was applied to obtain subdaily reconstructions of 24 historical EPEs that occurred in the territory of the Czech Republic between 1960 and 2001.
Hourly pluviograph records were used as reference data for verification of the reconstructions. In addition, the reconstructed precipitation (adjusted model precipitation) was compared with the raw model precipitation to objectively assess the improvement/deterioration of the precipitation reconstruction using the presented method.
The verification was performed using a "fuzzy" point-based approach that considers the model precipitation not only in the pixel where the pluviograph is located but also in neighbouring pixels. The results show that the adjusted model precipitation is in good agreement with pluviograph records in the majority of the reconstructed EPEs, especially if a larger neighbourhood area is considered.
In agreement with our previous results, the application of the reconstruction method improves precipitation reconstructions in cases of local convective precipitation. Widespread, predominantly stratiform precipitation is usually well reforecasted by the NWP model; therefore, the presented method does not significantly improve the reconstruction.