Abstract
Changes in the frequency of occurrence of atmospheric circulation patterns under a changing climate system has important implications for regional climate variability. While many studies have focused on understanding the trends in the atmospheric pattern amplitudes and probabilities of occurrence, little attention has been given to how the linkages between climate variables and the large-scale patterns have been changing. Here we first document the strengthening relationship between an important North Pacific teleconnection - the East Pacific/North Pacific (EP/NP) pattern – and United States (US) temperature variability since the 1950s. The EP/NP pattern is linked to tropical convection, and consistently the coherence between US temperature anomalies and tropical convection anomalies has also been increasing during the same time period. This upward trend in convection-temperature alignment is most notable during autumn and winter and is absent during the summer. The relationship strengths and trends further suggest that the EP/NP pattern should be incorporated into monthly and seasonal outlooks that are of broad importance to agriculture, industry, and fisheries.
Highlights
A competing hypothesis to the Arctic-weather linkage one is that recent prominent atmospheric circulation and associated climate anomalies across North America were related to tropical and North Pacific SSTs17–20 and that a wavier jet stream is the cause of Artic ice decline rather than the response to it[21,22,23,24]
We show that the upward trends in Eastern Pacific/North Pacific (EP/NP)-temperature relationship strengths has resulted in a greater number of United States (US) climate divisions for which the EP/NP pattern dominates the temperature variability
The results suggest that EP/NP index may be most useful in temperature prediction across the eastern US
Summary
A competing hypothesis to the Arctic-weather linkage one is that recent prominent atmospheric circulation and associated climate anomalies across North America were related to tropical and North Pacific SSTs17–20 and that a wavier jet stream is the cause of Artic ice decline rather than the response to it[21,22,23,24]. Despite the studies showing tropical and North Pacific linkages to US temperature, the Arctic Oscillation (AO, refs 25 and 26) index still remains one of the most widely used metrics to predict extratropical temperature variability because extreme values of the AO index are preceded by sudden stratospheric warming events with appreciable lead times[27, 28]. Been given to understanding how relationship strengths between the pattern and climate parameters have been changing Such changes are important to identify and understand because of the implications for weather and seasonal prediction. We show that the upward trends in EP/NP-temperature relationship strengths has resulted in a greater number of US climate divisions for which the EP/NP pattern dominates the temperature variability. The monthly US historical climate divisional data[34] are used in this study (see Supplementary Figure S1). The step was necessary for the scale-averaged coherence analysis (see Methods and Supplementary Material)
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