The North Pacific as regulator of summertime climate over Eurasia and North

• Main Authors: K. -m. Lau, J. -y. Lee, K. -m. Kim, I. -s. Kang
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Pacific; North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.589.5671; http://climate.snu.ac.kr/2005_new/pub/papers/p66.pdf

The role of the North Pacific as a regulator of boreal summer climate over Eurasia and North America is investigated using observational data. Two summertime interannual climate modes associated with sea surface temperature (SST) variability in the North Pacific are identified. The first mode shows an elongated zone of warm (cold) SST anomalies in the central North Pacific along 408N, with temporal variability significantly correlated with El Niño during the preceding spring, but its subsequent evolution is quite different from El Niño. The second mode exhibits a seesaw SST variation between the northern and southern North Pacific and is independent of El Niño. Both modes are linked to coherent SST anomalies over the North Atlantic, suggesting the presence of an ‘‘atmospheric bridge’ ’ linking the two extratropical oceans. Using the principal component of the most dominant mode as the North Pacific index (NPI), composite analyses show that the positive (negative) phase of NPI features a warm (cold) North Pacific associated with the formation of contemporaneous low-level stationary anticyclones (cyclones) over the North Pacific and North Atlantic, respectively. The anticyclones (cyclones) are linked by quasi-zonally symmetric circulation anomalies in the middle to upper troposphere spanning Eurasia and North America, accompanied by a poleward (equa-torward) shift of the subtropical jet and storm tracks. Associated with the positive (negative) phase of NPI, are