Abstract
Abstract. Characteristics of rainfall events in an ensemble of 23 regional climate model (RCM) simulations are evaluated against observed data in the Czech Republic for the period 1981–2000. Individual rainfall events are identified using the concept of minimum inter-event time (MIT) and only heavy events (15 % of events with the largest event depths) during the warm season (May–September) are considered. Inasmuch as an RCM grid box represents a spatial average, the effects of areal averaging of rainfall data on characteristics of events are investigated using the observed data. Rainfall events from the RCM simulations are then compared to those from the at-site and area-average observations. Simulated number of heavy events and seasonal total precipitation due to heavy events are on average represented relatively well despite the higher spatial variation compared to observations. RCM-simulated event depths are comparable to the area-average observations, while event durations are overestimated and other characteristics related to rainfall intensity are significantly underestimated. The differences between RCM-simulated and at-site observed rainfall event characteristics are in general dominated by the biases of the climate models rather than the areal-averaging effect. Most of the rainfall event characteristics in the majority of the RCM simulations show a similar altitude-dependence pattern as in the observed data. The number of heavy events and seasonal total precipitation due to heavy events increase with altitude, and this dependence is captured better by the RCM simulations with higher spatial resolution.
Highlights
Potential changes in characteristics of precipitation due to climate change may have significant societal impacts
The regional climate model (RCM)-simulated rainfall event characteristics are evaluated with respect to the observed data for the validation period (1981–2000) using ratios of mean characteristics, quantile ratios, and histogram ratios
This study presents a methodology for analysis of precipitation characteristics in RCM simulations from an event-based perspective
Summary
Potential changes in characteristics of precipitation due to climate change may have significant societal impacts. Several studies have reported significant changes in daily precipitation extremes in observed data Alexander et al, 2006; Trenberth, 2011; Westra et al, 2014) as well as in climate model projections (e.g. Kyselý et al, 2011; Hanel and Buishand, 2012; Madsen et al, 2014). The climate change scenarios for precipitation are frequently based on simulations of regional climate models (RCMs). RCMs usually rely, on convection parameterization schemes, even though these are known sources of significant uncertainties and errors (Brockhaus et al, 2008; Hohenegger et al, 2008; Kendon et al, 2012). That is especially the case for the simulated sub-daily precipitation (Westra et al, 2014)
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