Rainfall variability in Bulgaria and its relation with
Rainfall variability in Bulgaria and its relation with North Atlantic oscillation Nina Nikolova Sofia University “St. Kliment Ohridski” Bulgaria e-mail: nina@gea. uni-sofia. bg
Rainfall variability in Bulgaria and its relation with North Atlantic oscillation • Main questions: 1) whether the observed trend of rainfall variability in Bulgaria corresponds to the global climate change? 2) what is the influence of the NAO of rainfall variability in Bulgaria
Rainfall variability in Bulgaria and its relation with North Atlantic oscillation STUDY AREA Data - monthly and annual precipitation totals (investigated period is 1931 – 2000) - NAO indices
Rainfall variability in Bulgaria and its relation with North Atlantic oscillation Meteorological stations in Bulgaria under the present study
Rainfall variability in Bulgaria and its relation with North Atlantic oscillation STUDY AREA Methods - linear regression - correlation analysis
Rainfall variability in Bulgaria and its relation with North Atlantic oscillation REZULTS Linear regression Vasilev (1996), Vekilska &. Rathcev (2000), Velev (1996, 2000), Zlatunova & Penkov (2002) During the 1981 – 1990 the precipitation are 10 % lower than precipitation during the 1961 – 1990 and during 1985 – 1995 the decrease is bigger (Koleva, 1995)
Rainfall variability in Bulgaria and its relation with North Atlantic oscillation REZULTS Linear regression
Rainfall variability in Bulgaria and its relation with North Atlantic oscillation REZULTS Correlation between annual precipitation totals and NAO
Rainfall variability in Bulgaria and its relation with North Atlantic oscillation REZULTS Correlation between monthly precipitation totals and NAO 1931 - 2000
Rainfall variability in Bulgaria and its relation with North Atlantic oscillation REZULTS Correlation between monthly precipitation totals and NAO 1961 -2000
Rainfall variability in Bulgaria and its relation with North Atlantic oscillation CONCLUSION • negative trends for monthly and annual precipitation totals • correlation between rainfall and NAO: - negative for most of months and annual values - well established for wintertime
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