Extended Abstract (436K)JP5.6
Interannual and interdecadal variability in the Pacific region SST anomaly patterns and their impact on local climate
Anthony R. Lupo, University of Missouri, Columbia, MO; and F. A. Akyuz, I. I. Mokhov, E. P. Kelsey, D. K. Weitlich, and J. E. Woolard
Previous research by Kung and Chern (Atmosfera, 1995) has demonstrated that Pacific Region SSTs and SST anomalies can be separated into seven general synoptic classifications (“clusters”) for Pacific Region SSTs and SST anomalies (A-G). Each of these clusters is shown to have a distinct impact on the barotropic component of the mean tropospheric height distributions as well. Clusters A, B, E, and G (C, D, and F) are shown to be representative of La Nina (El Nino) type SST distributions. Further, an analysis of the SST patterns from 1955 – 1993 demonstrated that clusters A – D (especially A and B-type) were prominent from 1955 – 1977, while types E and F dominated the later period. Type G clusters were comparatively rare, but occurred in both periods. In retrospect, this shift in prominent patterns during 1977 corresponds roughly with a change in phase of the Pacific Decadal Oscillation (PDO). It is suggested here that after updating the analysis to include the 1994 to 2003 period, there was a corresponding change in the predominant SSTs associated with a change in phase of the PDO during 1999 and 2000. The results show that during this period, SST patterns did evolve from predominantly E and F-type anomalies during 1994 to A, B, D, and G-type anomalies through 2002 and into mid-2003. By July 2003, an El Nino resulted in the transition of the SST distributions to a D-type pattern, and then to A and B type anomalies. Thus, these results suggested that A through D-type SST clusters are characteristic of the negative phase of the PDO, while C, E, and F type are more characteristic of the positive phase of the PDO. Also, in spite of forecasts for a warmer than normal winter in the northern states, the winter of 2002 – 2003 was cooler than normal for this region. This indicates that the association of warm winters with El Nino conditions may need to be revised. Also, B and G anomalies tend to be associated with warmer-than-normal conditions in the mid-west, while C, D, and E type anomalies tend to be cooler than normal. C, F, and G anomalies were associated with drier than normal conditions across the mid-west, and the other SST anomalies did not produce definite results. Additionally, using an improved technique for generating phase diagrams, it is shown that there are significant interannual and interdecadal variations in the mid-Mississippi region monthly mean surface temperatures and precipitation records associated with the ENSO and PDO.
Joint Poster Session 5, Climate Variability (JOINT with THE 15TH SYMPOSIUM ON GLOBAL CHANGE AND CLIMATE VARIATIONS AND THE 14TH CONFERENCE ON APPLIED CLIMATOLOGY; Hall 4AB)
Wednesday, 14 January 2004, 2:30 PM-4:00 PM, Hall 4AB
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