Time series analysis of the delta (super 2) H, delta (super 18) O and d (sub excess) values in correlation with monthly temperature, relative humidity and precipitation in Ramnicu Valcea, Romania; 2012 to 2018

To investigate the influence of local climate and transboundary circulation of moisture on the stable isotope of precipitation in Ramnicu Valcea, Romania, monthly values of delta (super 2) H, delta (super 18) O, deuterium excess (d (sub excess) ), temperature, relative humidity and precipitation were determined between January 2012 and December 2018.Monthly analysis showed differences in d (sub excess) varying between 24.2 ppm (October 2015) and -23.7 ppm (July 2013) with a multi-annual average of 6.1+ or -5.9 ppm, suggesting an Atlantic origin of moisture with episodic Mediterranean transport. Also it was noticed a significant correlation between the North Atlantic Oscillation on the local temperature during winter season. The Local Meteoric Water Line (LMWL) for the entire period showed slope and intercept values similar to neighboring localities with the same altitude. When the analyze was extended to summer (April-October) and winter (November-March) seasons, the LMWL slope and intercept were different, reflecting the summer-winter difference of temperatures and air circulation. The monthly values of all parameters formed equal spaced Time Series (TS) whose detailed analysis confirmed at p<0.01 that delta (super 2) H, delta (super 18) O, temperature and relative humidity show a well evidenced one year periodicity. By contrast, precipitation and d (sub excess) seasonality were almost unrecognizable, most probably due to the reduced number of observations.