Investigation of precipitation and stream-flow variations in the Biga Peninsula and associations with the atmospheric oscillation indices

The aim of this study is to determine long-term changes and trends in airtemperature, precipitation and streamflow series in Biga Peninsula and itssurroundings. In addition, the linkages between interannual variations ofclimatological/hydrological series and several atmospheric oscillation indices wereinvestigated. According to results of Mann-Kendall test, mean, maximum andminimum air temperatures have generally tended to increase in all seasons exceptautumn. The decreasing trend in winter precipitation started in 1970?s and graduallybecome evident in 1990?s.A statistically significant negative correlation was found in winter betweeninterannual variability of mean, maximum and minimum air temperatures and theNorth Atlantic Oscillation (NAO), Mediterranean Oscillation (MO) and ArcticOscillation (AO) indices, except the El Niño-Southern Oscillation (EÑSO). Springair temperatures were found strongly and positively correlated with the EÑSO. Theconnection is strongest for minimum air temperature.In the study, canonical correlation analysis was also applied for determiningeffects of the atmospheric teleconnection patterns on mean, maximum and minimumair temperatures and precipitation total data. According to the canonical correlationanalysis, there are diagnostic effects of the AO, MO and NAO indices over all winterair temperature series. While AO is effective inner part of study area, the NAO andMO indices are most effective on the coastal zone. In spring, all air temperatureseries are better explained with the EÑSO, whereas the NAO variability betterexplains interannual variations in summer air temperatures. On the other hand,interannual variations in all autumn air temperatures are closely explained with theAO. The most apparent influence among the atmospheric oscillation indices onprecipitation total series is of the AO and NAO in winter. The AO and NAO indiceshave an influence on precipitation in spring, while the summer precipitation is mostlycharacterized with the local influences. Year-to-year variability of the NAO and AObetter explain year-to-year variability in autumn precipitation.