On the observed relationships between variability in sea surface temperatures and the atmospheric circulation in the Northern Hemisphere.

摘要

The advent of increasingly high-resolution satellite observations and numerical models has led to a series of advances in our understanding of the role of midlatitude sea surface temperature (SST) in climate variability, especially near western boundary currents (WBC). For example, recent observational analyses suggest that ocean dynamics play a central role in driving interannual SST variability over the Kuroshio-Oyashio and Gulf Stream Extension regions, and recent numerical experiments suggest that variations in the SST field in the Kuroshio-Oyashio Extension region may have a much more pronounced influence on the atmospheric circulation than previously thought. We assess the observational support for (or against) a robust atmospheric response to midlatitude ocean variability in the Kuroshio-Oyashio and Gulf Stream Extension regions. We apply lead/lag analysis based on daily data to assess relationships between SST anomalies and the atmospheric circulation on transient timescales, building off of previous studies that have applied a similar methodology to weekly data. In addition, we employ a novel approach to separate the regressions into an "atmospheric forcing" pattern and an "atmospheric response" pattern through spatial linear decomposition. The analysis reveals two distinct patterns associated with midlatitude atmosphere/ocean interaction in the vicinity of the major Northern Hemisphere WBCs: 1) a pattern that peaks 2-3 weeks before the SST anomalies (the "atmospheric forcing") and 2) a pattern that peaks after the SST anomalies (the "atmospheric response"). The latter pattern is independent of the former, and is interpreted as the signature of SST variability in the atmospheric circulation. Further analysis is required to understand if the "atmospheric response" pattern truly reflects the response to the SST anomalies within the WBC regions.