Abstract
In the past few years, demands on flash flood forecasting have grown. The Flash Flood Indicator (FFI) is a system used at the Czech Hydrometeorological Institute for the evaluation of the risk of possible occurrence of flash floods over the whole Czech Republic. The FFI calculation is based on the current soil saturation, the physical-geographical characteristics of every considered area, and radar-based quantitative precipitation estimates (QPEs) and forecasts (QPFs). For higher reliability of the flash flood risk assessment, calculations of QPEs and QPFs are crucial, particularly when very high intensities of rainfall are reached or expected. QPEs and QPFs entering the FFI computations are the products of the Czech Weather Radar Network. The QPF is based on the COTREC extrapolation method. The radar-rain gauge-combining method MERGE2 is used to improve radar-only QPEs and QPFs. It generates a combined radar-rain gauge QPE based on the kriging with an external drift algorithm, and, also, an adjustment coefficient applicable to radar-only QPEs and QPFs. The adjustment coefficient is applied in situations when corresponding rain gauge measurements are not yet available. A new adjustment coefficient scheme was developed and tested to improve the performance of adjusted radar QPEs and QPFs in the FFI.
Highlights
The purpose of this paper is to describe radar-based quantitative precipitation estimates (QPEs) and quantitative precipitation forecasts (QPFs) computation and its utilization for flash flood nowcasting at the Czech Hydrometeorological Institute (CHMI)
The radar-only QPE is based on the PseudoCAPPI 2 km radar product [17,18], which was identified to be optimal for rainfall estimates over the territory of the Czech Republic [6]
The local bias (LB) field is not computed for each individual rain gauge, because based on its large spatial variability, it yields much worse results when applied to the QPF
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The Czech Hydrometeorological Institute (CHMI) is the national weather service of the. Czech Republic and, as such, it operates the Czech Weather Radar Network (CZRAD) [1,2]
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