Comparative Analysis between Daily Extreme Temperature and Precipitation Values Derived from Observations and Gridded Datasets in North-Western Romania (original) (raw)

Changes in precipitation extremes in Romania

Changes in daily extreme precipitation have been identified in many studies conducted at local, regional, or global scales. In Romania, little research on this issue has been done. The present study focuses on the analysis of the trends in daily extreme precipitation indices over a period of 53 years (1961e2013). Data sets of daily precipitation recorded in 34 weather stations were analyzed. Among them, three are located in the Carpathians and four on the Black Sea Coast. The main goal was to find out changes in extreme daily precipitation using a set of 13 indices adopted from the core indices developed by ETCCDMI adapted to suit to the studied area. The series of indices and their trends were generated using RClimDex software. The trends have been calculated by employing modified ManneKendall test and Sen's slope. Generally, the climate of Romania has become wetter over the 53-yr period considered, especially in the northern regions, although the spatial distribution of the significant trend slopes in the area is extremely irregular. Based on fixed threshold indices analysis, extreme precipitation events are characterized by a decreasing in the total number of precipitation days (R0.1), and a dominant increasing trend for the number of isolated days with moderate and heavy precipitation (R5, R10).

Investigation of climate extremes in the Carpathian region on harmonized data

2013

Climate change is expected to result in significant changes in Carpathian region due to more frequent extreme events. Studying the spatio-temporal changes of climate extremes can be implemented through the analysis of observations reliable in time and in space. Numerous climate indices are used in several projects on climate change as prevailing indicators of changes in extremes. The homogenized (MASH (Szentimrey)) and gridded (MISH (Szentimrey and Bihari)) datasets created in the frame of the CARPATCLIM are used in this study for investigations. The temporal resolution of the gridded database is daily for period 1961-2010, the spatial resolution is 0.1°. Many basic meteorological variables were homogenized and interpolated on this grid for the 50 years long time frame from 1961 to 2010 (Szalai et al., 2011). The harmonized database achieved in the project provides relevant outcomes for studying extremes. Several temperature and precipitation indices are calculated in this study for...

Seasonal and annual extreme temperature variability and trends of the latest three decades in Romania

2013

It was anticipated that every region in Europe will be negatively affected by the future climate changes. The latest European studies concluded that the intensity of extreme temperatures increased more rapidly than the intensity of more moderate temperatures over the continental interior due to increases in temperature variability. At the same time in many regions there is an asymmetry in the warming that undoubtedly will contribute to heterogeneity in ecological dynamics across systems. The objective of this work was to identify spatial variations of the seasonal and annual extreme temperature variability and trends over Romania in the period 1982-2011. Starting with a large climatological database (30 years of daily data for 29 locations from Romania), daily minimum, maximum and amplitude temperature data were condensed into normal probability functions for which the assumption of normal distribution was accepted by the Shapiro-Wilk statistical test (SPSS 14.0, USA). These functio...

Spatial and temporal variability of climate extremes in Romania and associated large-scale mechanisms

International Journal of Climatology, 2014

The simultaneous variability of several climate extremes in Romania on the one hand and the understanding of the large-scale mechanisms responsible for this variability on the other are examined. Ten indices associated with temperature and precipitation extremes computed at high spatial resolution for the period 1961-2010 are analysed. Significant increasing trends for the temperature extremes are detected in all seasons, except for autumn, with the highest increasing rate in summer and the lowest in spring. Regarding precipitation extremes, significant increasing trends over large areas in the frequency of very wet days and maximum daily amount during autumn and in the maximum duration of dry spells during summer are the only ones detected.

Regional analysis of extreme temperature and precipitation indices for the Carpathian Basin from 1946 to 2001

Global and Planetary Change, 2007

Since human and natural systems may be especially affected by changes of extreme climate events, the main objective of our research is to detect the possible changes of intensity and frequency of these extreme events. Several climate extreme indices are analyzed and compared for Central/Eastern Europe (focusing on Hungary) for the 20th century based on the guidelines suggested by the joint WMO-CCl/CLIVAR Working Group on climate change detection. These climate extreme indices include the numbers of severe cold days, winter days, frost days, cold days, warm days, summer days, hot days, extremely hot days, cold nights, warm nights, hot nights, the intra-annual extreme temperature range, the heat wave duration, the number of wet days (using several threshold values defining extremes, i.e., 10 mm and 20 mm), the maximum number of consecutive dry days, the highest 1-day precipitation amount, the greatest 5-day rainfall total, the simple daily precipitation intensity, the numbers of moderate wet days and very wet days, the annual fraction due to extreme precipitation events, etc. Therefore, daily maximum, minimum and mean temperature observations (from 13 stations) and daily precipitation amounts (from 31 stations) are used in the present statistical analysis. Our results suggest that similarly to the global and continental trends, regional temperature of Central/Eastern Europe has become warmer during the second half of the 20th century. Specifically, the strongest increasing tendency is detected in case of the annual numbers of hot days, summer days, warm days, warm nights, and the heat wave duration index. Before this warming period in the last quarter of the 20th century, most of the indices exhibit a cooling period until the middle of the 1970's. Furthermore, regional intensity and frequency of extreme precipitation has increased (as shown by the annual fraction due to extreme precipitation events, and the numbers of moderate wet days, very wet days, and very heavy precipitation days) between 1976 and 2001, while the total precipitation has decreased (as shown by numbers of precipitation days exceeding 0.1 mm, 1 mm, and 5 mm) in the region.

Variability of climate extremes in Romania and associated large-scale mechanisms

The simultaneous variability of several climate extremes in Romania on the one hand and the understanding of the large-scale mechanisms responsible for this variability on the other are examined. Ten indices associated with temperature and precipitation extremes computed at high spatial resolution for the period 1961-2010 are analysed. Significant increasing trends for the temperature extremes are detected in all seasons, except for autumn, with the highest increasing rate in summer and the lowest in spring. Regarding precipitation extremes, significant increasing trends over large areas in the frequency of very wet days and maximum daily amount during autumn and in the maximum duration of dry spells during summer are the only ones detected.

Some Aspects on Rainfall Maximum Intensity in Northwestern Romania

13th SGEM GeoConference on ENERGY AND CLEAN TECHNOLOGIES, 2013

As a consequence of the global warming we assist in the last decades at the intensification of extreme weather or hydrological events, such as droughts, hail storm or flash floods . This paper examines some spatial and temporal manifestations of maximum intensity of rainfall in the warm season, in Northwestern Romania. Diurnal variation, duration, and intensity of the maximum rainfall intensity as well as the return periods of the absolute values, the statistical probability of recording higher values and trends have been detected. Annual maximum intensity values of precipitation recorded in 14 weather stations over a period of 35 years ) have been considered. HYFRAN and MAKESENS software have been employed for statistical analysis. The data sets were tested to check if they were identical and independent distributed at the 95% of significance level. The main findings are: maximum intensity extreme values varies between 5.0 and 10.) mm/min; the highest frequency of rainfa ll maximum intensity is specitic in the afternoon and in the evening; the frequency of events with certain maximum intensity duration dramatically decreases from 45 .5 % for 1 minute period to 0.6 % in the case of those events lasting more than 8 minute; the return periods of absolute maximum intensities are generally ranging between 30 and 80 years, wh,jJe the absolute minimum intensities have the return periods between 1.002 and 1.06 years; almost 80 % of the locations indicated increasing trends in the maximum intensity of rainfall. All these findings are very important for modeling the flash flood parameters.

On the Examination of the Relationship between Mean and Extreme Precipitation and Circulation Types over Southern Romania

Atmosphere

The main goal of the present study is to identify the prevailing atmospheric circulation patterns (circulation types) that are associated with the occurrence of precipitation (both mean and extreme) over southern Romania. A daily circulation type calendar derived from an automatic and objective classification scheme is used in synergy with the daily precipitation time series from five weather stations in the study area for a sixty-year period (1961–2020). Both mean and extreme precipitation do not show statistically significant trends, except for the annual precipitation at Constanța, for the value with daily precipitation totals greater than the 95th percentile at Craiova and the number of days exceeding the 99th percentile at Buzău and Râmnicu -Vâlcea, where significant negative trends were noticed. Moreover, the precipitation trends were analyzed in relation to the atmospheric circulation types. Non-significant positive trends were observed for the precipitation amounts (annually...