Analysis of short-term precipitation for design purposes at Hungarian Meteorological Service

The water cycle has accelerated, and warmer air can hold more moisture, increasing the risk of heavy and intense downpours. This intensification of rainfall makes it necessary to update the rainfall intensity-duration-frequency (IDF) curves that were originally developed for stormwater drainage design in the 1970s in Hungary. Recently the previously used uniform functions was replaced with locally tailored maximum rainfall distribution functions that better reflect the climatic conditions at the planned drainage site.

Estimating the parameters of Generalized Extreme Value (GEV) distributions to compute the return values requires time series of precipitation data for short durations such as 10, 20, or 30 minutes. Once these data are available, after fitting the GEV function, the Intensity-Duration-Frequency (IDF) curves can be constructed. These curves allow for determining the return period of a given precipitation intensity over a specified duration.

HungaroMet has developed a service to support design applications, mainly used for drainage systems. The downloadable intensity values are based on automatic measurements from 100 monitoring sites. After entering the location of the planned project, users can access site-specific intensity values for planning purposes. As the measurement time series continue to grow, the design values can be regularly updated using the most comprehensive data available in the HungaroMet database.

To better reflect the effects of climate change, in addition to the IDF curves based on observations, we are analysing daily “prhmax” values (daily maximum hourly precipitation intensity) from six regional climate model simulations from the EURO-CORDEX selection, recently used at Hungarian Meteorological Service. The analysis covers three emission scenarios and two future time periods: 2041–2070 and 2071–2100.  The aim is to use the “prhmax” for calculating return values of short-term precipitation for design puposes.

"This work has been implemented by the National Multidisciplinary Laboratory for Climate Change (RRF-2.3.1-21-2022-00014) project within the framework of Hungary's National Recovery and Resilience Plan supported by the Recovery and Resilience Facility of the European Union."