Undergraduate Research and Creativity

URECA

2008-2009

Characteristics of extreme temperatures in coastal waters of North America

Karen Bubelnik and Kamazima Lwiza
School of Marine and Atmospheric Sciences

This study uses daily sea surface coastal temperature records from four stations from the west coast and one station from east coast in USA to examine characteristics of temperature extremes in coastal waters. Quantiles of winter and summer temperatures from 1945 to 2006 are used to examine seasonal extremes and their statistical characteristics. More than 70% of the interannual variability in the extremes is driven by the interannual variations in the mean temperature, and the probability distribution functions are approximately invariant with time. The wavelet analysis reveals significant peaks at periods of 3, 4-6, 16-20 years for winter extremes. The energy for summer extremes is significant at 2-3 and 4-8 years between 1920 and 1940. Then the system goes into a quiescent period between 1940 and 1955 followed by peaks which operate between 3-6 and 14-18 years. Processes operating at long time scales (14-18 years) seem to be transcontinental because they exist on both coasts at about the same time. Short-time scale (<5 years) processes seem to be driven by local processes on each coast and each station. It seems that large-scale ocean variations, e.g., Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), and Arctic Oscillation (AO) seem to exert strong influence on the coastal extreme temperatures. However, their exact individual contributions to the extreme variability are not clear because their frequencies are very similar. The stationarity of the centered quantiles of the extremes implies that for each station we can use one extreme value distribution function for each season. This would be useful for predictions of extreme temperatures of future climatic scenarios.