engleski

HyMeX activities in Croatia during SOP1

The HYdrological cycle in the Mediterranean EXperiment (HyMeX) is intended to improve the capabilities to predict high impact weather events. In its framework, the first Special Observation Period (SOP1), 5 September to 6 November 2012, was aimed to study heavy precipitation events and flash floods. Here we present high impact weather events over Croatia that occurred during SOP1. A particular attention is given to eight Intense Observation Periods (IOP)s during which high precipitation occurred over the eastern Adriatic and Dinaric Alps. During the entire SOP1, the operational models forecasts generally represented well medium intensity precipitation, while heavy precipitation was frequently underestimated by the ALADIN model at 8 km grid spacing and overestimated at higher resolution (2 km grid spacing). During IOP2 intensive rainfall occurred in wider area of the city of Rijeka in the northern Adriatic. Short-range maximum rainfall totals achieved maximum values ever recorded at Rijeka station since the beginning of measurements in 1958. The rainfall amount measured in intervals of 20, 30 and 40 minutes are exceptional with return periods of more than thousand, few hundreds and hundred years respectively. The operational precipitation forecast using ALADIN model at 8 km grid spacing provided guidance on the event but underestimated the rainfall intensity. Evaluation of numerical sensitivity experiments suggested that forecast was slightly enhanced by improving the initial conditions through variational data assimilation. The operational non-hydrostatic run at 2 km grid spacing using configuration with ALARO physics package further improved the forecast. This article highlights the need for an intensive observation period in the future over the Adriatic region, to validate the simulated mechanisms and improve numerical weather prediction via data assimilation and model improvements in description of microphysics and air-sea interaction.

HyMeX SOP1, heavy precipitation, ALADIN, Adriatic Sea, air-sea interactions

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