Teleconnection Influences on Extreme Daily Temperatures in California, 1950-2005.

Frequencies of extreme daily temperature events are compared between high and low phases of two teleconnection patterns that affect California—the Pacific/North America (PNA) pattern and the Southern Oscillation Index (SOI, representing ENSO). The positive phase of the PNA is associated with an increased number of hot extremes, especially in fall and winter, along with a decrease in winter and spring cold extremes. The positive phase of the SOI corresponds to an increased frequency of extreme events in both maximum and minimum temperatures, with the most effect on minimum temperatures in spring. Variations in these relationships with changes in the phase of the Pacific Decadal Oscillation (PDO) are also examined—the PNA pattern produces fewer cold extremes when the PDO is positive, and the difference is larger for the negative PNA. The positive SOI produces more spring hot events and fewer cold events when the PDO is also positive. [ABSTRACT FROM AUTHOR]