Thursday, 18 January 2007: 11:30 AM
Impact and indicator based perspectives of ENSO influence on U.S. climate during winter
214B (Henry B. Gonzalez Convention Center)
Traditional ENSO impact analysis is recast to investigate the boreal winter teleconnections between U.S. climate and varying indicator regions of SST anomalies in the tropical Pacific. This serves the dual purpose of finding a targeted indicator region for a particular impact zone (i.e. a localization of the teleconnection pattern) and indirectly assessing the viability of well-established ENSO indices (i.e. the Niño indices). Based on a selection of impact grid points with known ENSO responses, it appears that the most appropriate indicator region often varies from one impact grid point to another, as well as from warm SST phase to cold SST phase. In addition, air temperature composites behave differently than precipitation composites. In order to simultaneously consider the “impact perspective” detailed above with the typical “indicator perspective” (in which climate impacts are computed based on the well-established Niño indices), EOF analysis of composited climate fields, conditioned on SST phase, as functions of indicator region and impact zone was performed. The resulting modes represent indicator-impact pairs. Each mode has an impact amplitude function (a spatial temperature or precipitation anomaly signature over the impact region) and an associated indicator weighting function, which modulates the impact amplitude function based on the location of the indicator region. Based on this approach, the unusual, yet well-established, La Niña air temperature impact over the U.S. when using the Niño 1+2 region is accounted for as the superposition of two EOF modes. In addition, a teleconnection between tropical Pacific SST and Southeastern U.S. temperature anomalies is documented that appears to be unrelated to ENSO.