engleski

Extreme precipitation event over the Northern Adriatic during the HyMeX SOP1-IOP2

During the late evening hours of 12th September 2012 a rainy episode with very heavy rain falling over only a few hours have been recorded over the city of Rijeka at the northern coast of Kvarner Bay in the eastern Adriatic sea and its mountainous hinterland of Gorski kotar in Croatia. During the event, record breaking precipitation of 46.7 mm / 20 min was measured. According to the report of the Municipal Water and Sewer Company of the city of Rijeka (http://www.youtube.com/kdvik ) some major city roads became rivers and streams, sewage manhole covers were discharged and massive caps flew into the air up to two meters, and then a spate of them were carried up to one hundred meters away from the shaft. This event coincides with the HyMeX SOP1/IOP2 field campaign over the western Mediterranean and NE Italy. The event was associated to a warm and moist low level air-mass from the Adriatic Sea and a cold air outbreak crossing the Alps which resulted with the appearance of squall-line in the late afternoon and evening. Rain-gauges recorded a 24 hourly precipitation up to 160 mm over the north-eastern Italy and reaching 220 mm in Rijeka. A peak intensity of 85.3 mm in one-hour period was registered from 21 to 22 UTC, with 20.6 and 51.7 mm/h in the previous and the following hour. A detailed insight into the temporal rainfall distribution during the short-term interval of this heavy rainfall event is provided by an ombrograph at the meteorological station Rijeka. Maximum 20, 30, 40, 50, 60 and 120 minutes rainfall totals, measured during the most intense part of the rainfall episode, have not been recorded at Rijeka station since the beginning of measurements in 1958. Especially intense were the rainfall intervals of 20, 30 and 40 minutes that could be expected once in a more than thousand, few hundreds and hundred years respectively, and they belong to the extraordinary rare event. The maximum amounts that fall in the interval of two and four hours could be expected ones in 40 and 50 years respectively. Operational forecasts did forecast rainfall amounts exceeding 100 mm in 24 hours, but most forecast runs put the area of maximum intensity over Slovenia, and only one operational forecast run moved the high intensity precipitation towards Rijeka. This study has highlighted the need for a dense network of observations, especially radar measurements, to validate the simulated mechanisms and improve the numerical forecasts through data assimilation.

HyMeX SOP1/IOP2; HPE; Rijeka; statistical estimation; numerical forecast

nije evidentirano