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The paper analysis the precipitations associated to the cut-off lows and their regional distribution induced by the air circulation types and the position of cut-off lows in relation to the different regions of the country, in Romania in 2014. Cut-off lows have been identified using geopotential, air temperature and circulation maps at 500 and 300 hPa levels within the region of latitude 40 to 50 °N and longitude 15 to 35 °E. To establish the atmospheric circulation type for each cut-off event, HYSPLIT model was used (Draxler and Rolph, 2012). Based on the daily precipitation data for the year 2014 from 150 meteorological stations from Romania, divided into historical and geographical regions, the total amount of precipitation for each cut-off low event was determined. It was also calculated the monthly and annual amount of precipitation for each weather station and the ratio between the monthly (and annual) amount of precipitation and those associated to the cut-off lows. The most important findings are: 13 cases of cut-off lows were identified, the highest number in July (3 cases); in most of the cases the cut-off lows lasted for 2 days (5 cases), the longest case having 8 days; the most significant amounts of precipitation were recorded in May and April, and the highest value recorded exceeded 100 mm (125.7 mm in Banat region); masses of air reach in moisture advected from the south (S, SV, SE) and west (V, NV), recorded a high frequency; high percentages of precipitations induced by cut-off lows from the total rainfall of the year were recorded in the regions situated in the south, east, south-west and west part of Romania as a consequence of air circulation types generating cut-off lows existence. [ABSTRACT FROM AUTHOR]

The paper analyzes the frequency and trend of the rainfall amounts of the rainy periods lasting 2, 3 and 4 days, which occurred at 4 weather stations in MaramureŠ County, in the period 1961-2016. The homogeneity of the daily data set has been analyzed, using the methodology described by Wijngaard et al. (2003), based on Pettitt, Standard normal homogeneity, Buishand and von Neumann tests, at the 99% significance level and for the frequency analysis, HYFRAN software was used. Subsequently, the frequency of the precipitation amounts of the mentioned periods was calculated, using the method of equal intervals. The cumulative amounts in 2-day intervals show the highest frequency for Class 1 (0.2-6.5 mm), with a probability of occurrence of 45-55%, the cumulative amounts in 3 days for Classes 1 (0.4-7.4 mm) and 2 (7.5-14.5 mm), with a probability of 22-37%, and the cumulative amounts in 4 days for Class 2 (9.9-17.8 mm), with a probability of 21-30%. The decadal distribution of periods accumulating exceptional amounts of precipitation, ≥50 mm, was then analyzed and it was established that the maximum risk interval of their occurrence is June-September. The frequency, trend, degree of assurance and variability of the maximum annual rainfall quantities of the mentioned periods were also studied. The return periods of maximum annual rainfall quantities registered in 2-4 days are ranging between 29.8 and 580 years. [ABSTRACT FROM AUTHOR]

The paper analyzes some characteristics of annual and seasonal amounts of rainfall recorded in 24 hours in Romania. Annual and seasonal frequency distribution of rainfall quantities registered in 24 hours, air circulation type regarding these events, and the return periods of the absolute maximum values have been analyzed. Annual and seasonal values of maximum 24-hour precipitation amount from 23 weather stations from Romania, located between 3 and 661 m, have been considered over a period of 55 years (1961-2015). First, the data sets were tested using homogeneity distribution test at 99 % of significance level provided by XLSTAT software. HYFRAN software and HYSPLIT model have been employed in order to calculate statistics based on frequency analysis and to identify the atmospheric circulation type, respectively. The main findings are: absolute maximum annual rainfall quantities vary between 65.3 and 224.0 mm, with the highest values (over 120 mm) in the east and south-east part of the country; most of the weather stations have the highest annual frequency between 25- 50 mm, while winter, spring, and autumn are characterized by high frequency of 0-25 mm amounts; for the winter season, the maximum 24-hour precipitation has never exceeded 75 mm, in spring and autumn they are under the 125 mm threshold, while in summer locally exceeded 200 mm; the return periods of maximum annual quantities of rainfall are generally ranging between 32.2 and 387 years, highlighting the continental climate of some regions of the country; four types of air circulation have been detected, more frequent from south and southwest part of the Europe, bringing warm and moist air masses. [ABSTRACT FROM AUTHOR]

This paper analyzed the spatial and temporal variability of the rainy periods that occurred in the county of Maramureş. In this regard, daily precipitation data have been used from 4 weather stations, for the period 1961-2013. In the first stage the homogeneity of the daily data set has been analyzed, based on Pettitt, Standard normal homogeneity, Buishand and von Neumann tests, at the 1% significance level. The analyzed data belonged to Class 1 („useful"), as they reject the null hypothesis of 3 out of the 4 mentioned tests. Subsequently, the annual, monthly and seasonal number of rainy periods has been analyzed, the length of the periods, their frequency depending on length and their spatial and temporal variability. Based on the CurvExpert 1.37 program, the trend of the annual number of rainy periods depending on their duration was studied. The result was a total number of over 8100 periods, for the 4 stations. The number of rainy periods increases from the west to the east, once with the growth of land altitude. During a year may occur, on average, between 37-40 periods with an average length of 4-4.5 days. The length of the rainy periods varies between 2-35 days. The most periods are recorded in the intervals May-July and December-January. The most periods lasting ≥ 10 days, occurred in the decade 2001-2010 or 1961-1970. [ABSTRACT FROM AUTHOR]