Evaluation of extreme precipitation events at the sub-daily scale

0508681 - ÚFA 2020 DE eng A - Abstrakt
Müller, Miloslav - Bližňák, Vojtěch - Kašpar, Marek - Zacharov, Petr, jr. - Kvak, Róbert
Evaluation of extreme precipitation events at the sub-daily scale.
EMS Annual Meeting Abstracts, Vol. 16. Berlin: European Meteorological Society, 2019.
[EMS Annual Meeting 2019. 09.09.2019-13.09.2019, Copenhagen]
Institucionální podpora: RVO:68378289
Klíčová slova: Extreme precipitation events * numerical weather prediction * COSMO model
Obor OECD: Meteorology and atmospheric sciences
https://meetingorganizer.copernicus.org/EMS2019/EMS2019-648.pdf

Exact evaluation of extreme precipitation events (EPEs) is necessary mainly for climatological and hydrological
purposes. However, differences among EPEs in their spatial extent, intensity distribution, and duration make their
comparison extremely difficult. Therefore, there is no universal criterion for evaluation of EPEs. Everybody who
analyzes a set of EPEs within a region, must look for a proper tool for their selection and evaluation.
Frequently, EPEs are simply characterized either by maximum daily precipitation totals or by the areal means
of precipitation (usually for a fixed number of days). While the first criterion does not represent the size of the
affected area, the other one does not reflect the spatial concentration of precipitation within the considered region.
Using daily precipitation data from Central-European rain gauges (since 1961), we present significant differences
between the two sets of EPEs selected by the two criteria at several spatial levels. Moreover, we demonstrate the
fact that EPEs produced by convective storms tend to be significantly underestimated as they frequently last only
several hours in fact.
Therefore, we suggested the Weather Extremity Index (WEI) which combines the areal extent of the affected area
with return periods of precipitation totals there. Using daily precipitation totals, the index enables to compare
EPEs with different duration of several days because it can employ return periods of precipitation totals during up
to 5 or even more days. However, torrential rains remained underestimated in studies based on the WEI because
precipitation totals recorded even in one hour were considered as daily totals.
The presented study is based on two types of hourly precipitation data from Czechia. For selected historical EPEs,
hourly data were disaggregated from recorded daily totals by the NWP model COSMO. For the evaluation of EPEs
since 2002, we used radar-derived precipitation estimates adjusted by daily rain-gauge data. The latter dataset
was also used for the estimation of return levels of precipitation totals from 1 to 24 hours. The study proofs the
improvement of the evaluation procedure by the WEI when sub-daily precipitation totals and respective return
periods are employed.
Trvalý link: http://hdl.handle.net/11104/0299519