Changes in the winter precipitation in Romania and its relation to the large-scale circulation (original) (raw)
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Are the Regional Precipitation and Temperature Series Correlated? Case Study from Dobrogea, Romania
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In the context of climate change, this article tries to answer the question of whether a correlation exists between the precipitation and temperature series at a regional scale in Dobrogea, Romania. Six sets of time series are used for this aim, each of them containing ten series—precipitation and temperatures—recorded at the same period at the same hydro-meteorological stations. The existence of a monotonic trend was first assessed for each individual series. Then, the Regional time series (RTS) (one for a set of series) were built and the Mann–Kendall test was employed to test the existence of a monotonic trend for RTSs. In an affirmative case, Sen’s method was employed to determine the slope of the linear trend. Finally, nonparametric trend tests were utilized to verify if there was a correlation between the six RTSs. This study resulted in the fact that the only RTS presenting an increasing trend was that of minimum temperatures, and there was a weak correlation between the RTS ...
Winter precipitation variability and large-scale circulation patterns in Romania
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The spatial and temporal variability of winter precipitation and its links to the large-scale atmospheric circulation patterns in Romania are examined. The data set is composed of observed rainfall at 30 meteorological stations during the 1961-1996 period. The large-scale field is represented by the observed geopotential height at 500 hPa (Z500) over the same period, covering the latitudinal belt between 20 N-90 N (resolution 2.5 Â 2.5 ).
Variability of the precipitation regime for the first decade of XXI st century in southwestern Romania. The first decade of the XXI st century was a period marked by an increase in frequency of extreme weather events. The period analyzed in this paper (2001-2010) was characterized by a high variability in terms of spatial and temporal distribution of precipitation amounts recorded. Some absolute monthly and annual records of rainfall values have been exceeded during this decade in Oltenia (southwestern Romania), standing out the years 2007 and 2008, like dry years, and 2004 and 2005, as excessively rainy years. The aim of this paper is to analyze the spatial and temporal evolution of the annual amounts of rainfall recorded in southwestern Romania between 2001 and 2010. For this paper daily diagnostic data recorded in 14 synoptic weather stations in the Oltenia Regional Meteorological Center were used. The synoptic weather stations with reduced operating hours have been excluded from...
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Extreme events in Romania associated with large-scale atmospheric circulation
In the Northern hemisphere, the interaction between warm air from medium latitudes and polar cold air largely determines the weather regime throughout the year. In recent years, the European continent has been affected by extreme phenomena, such as severe floods or prolonged droughts. In Romania, the heating phenomenon follows the same trend of evolution, so that in the first decade of this century the average annual air temperature increased by about 0.4 °C, compared to the decade 1961-1970. In this paper were analyzed from a thermal and rainfall point of view, two extreme years, 2007, characterized by extremely hot winter and summer and 2010, during which the rainfall was surplus in almost all months. In order to detect whether the highlighting trend is real for these two seasons, statistical methods were applied to this data.
Changes in precipitation (P), evapotranspiration (ET) and, implicitly, in the climatic water balance (CWB), are imminent effects of climate warming. However, changes in the CWB, as a response to changes in P and ET, have not yet been analysed thoroughly enough in many parts of the world, including Romania. The present study explores the spatio-temporal changes of the CWB (difference between P and reference evapotranspiration, ET o) in Romania, based on a wide range of climatic data (P, as well as temperature, relative air humidity, sunshine duration and wind speed, necessary for computing ET o with the FAO-56 Penman-Monteith method) recorded at 70 weather stations across the country in the 1961–2013 period. As a secondary objective, the study attempts to identify the possible connections between the index's trends and large-scale atmospheric circulation, assessed based on the dynamics of certain European-scale relevant teleconnection indices. Thus, the Mann–Kendall test and Sen's slope methods were used to analyse CWB trends (but also P and ET o trends, in order to explain CWB pattern changes) annually, seasonally and in the maize and wheat growing seasons. Also, the Spearman correlation procedure and a composite analysis between interannual series of teleconnection indices and CWB were used to assess the influence of atmospheric circulation on the index's variability for all analysed time scales. The results generally showed CWB decreases (for the most part of up to −2 mm/yr, yet with a relatively low statistical significance) and highlighted an overall amplification of drier conditions on all time scales, except for autumn (CWB increases, generally of up to 1 mm/yr, but with low statistical significance). Moreover, net changes of even under −200 mm/53 yrs annually and −175 mm/53 yrs in summer and for the maize and wheat growing seasons were found in the CWB. Spatially, it was found that the country's southwestern and southeastern regions are the main epicentres of drier trends, while the northwest appears to have become wetter. Overall, the negative CWB trends are due to partial P decreases (statistically insignificant) and general ET o increases (highly statistically significant, even 100% in summer). It seems that the amplification of the climatic water deficit across the country is especially linked to the positive phases of the Arctic Oscillation and North Atlantic Oscillation, but also, in part, to those of several other teleconnection indices that affect Europe. Our results signal the necessity to adapt anthropic and ecological systems to future dryness trends countrywide, which will most likely intensify against the background of climate change expected to occur by the end of the century.
International journal of …, 2002
This paper investigates the temporal and spatial variability of the seasonal mean of maximum air temperature in Romania and its links with the large-scale atmospheric circulation. The Romanian data sets are represented by time series at 14 stations. The large-scale parameters are represented by the observed sea-level pressure (SLP) and geopotential height at 500 hPa (Z500). The period analysed was 1922-98 for winter and 1960-98 for all seasons. Before analysis, the original temperature data were tested to detect for inhomogeneity using the standard normal homogeneity test. Empirical orthogonal functions (EOFs) were used to analyse the spatial and temporal variability of the local and large-scale parameters and to eliminate noise from the original data set. The time series associated with the first EOF pattern of the SLP and mean maximum temperature in Romania were analysed from trend and shifts point of view using the Pettitt and Mann-Kendall tests respectively. The covariance map computed using the Z500 and the seasonal mean of maximum temperature in Romania were used as additional methods to identify the large-scale circulation patterns influencing the local variability.
Statistical Analysis of the Precipitation from Constanța (Romania) Meteorological Station
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This study is focused on the analysis of precipitation on the Eastern part of Romania, namely the Dobrudja region, since the water resources in the region are sensitive to climate change. The results of statistical analysis of precipitation data from Constanta meteorological station for the period 1885-2009 are presented. The statistical analysis indicates an increasing trend of the mean annual precipitation and the existence of some break points in the data series. After 1994, the mean annual precipitation increased by 100 mm, a value in agreement with existing estimations for the whole of Europe.