Affiliation:
1. a Department of Meteorology and Atmospheric Science, The Pennsylvania State University, University Park, Pennsylvania
Abstract
Abstract
Applying composite analysis to ERA-Interim data, the surface air temperature (SAT) anomaly pattern of the Pacific–North American (PNA) teleconnection is shown to include both symmetric and asymmetric SAT anomalies with respect to the PNA phase. The symmetric SAT anomalies, overlying the Russian Far East and western and eastern North America, grow through advection of the climatological temperature by the anomalous meridional wind and vertical mixing. The asymmetric SAT anomalies, overlying Siberia during the positive PNA and the subtropical North Pacific during the negative PNA, grow through vertical mixing only. For all SAT anomalies, vertical mixing relocates the temperature anomalies of the PNA teleconnection pattern from higher in the boundary layer downward to the level of the SAT. Above the level of the SAT, temperature anomaly growth is caused by horizontal temperature advection in all locations except for the subtropical North Pacific, where adiabatic cooling dominates. SAT anomaly decay is caused by longwave radiative heating/cooling, except over Siberia, where SAT anomaly decay is caused by vertical mixing. Additionally, temperature anomaly decay higher in the boundary layer due to nonlocal mixing contributes indirectly to SAT anomaly decay by weakening downgradient diffusion. These results highlight a diverse array of mechanisms by which individual anomalies within the PNA pattern grow and decay. Furthermore, with the exception of Siberia, throughout the growth and decay stages, horizontal temperature advection and/or vertical mixing is nearly balanced by longwave radiative heating/cooling, with the former being slightly stronger during the growth stage and the latter during the decay stage.
Funder
National Science Foundation
Publisher
American Meteorological Society
Reference38 articles.
1. Classification, seasonality and persistence of low-frequency atmospheric circulation patterns;Barnston, A. G.,1987
2. The ERA Interim Archive: Version 1.0;Berrisford, P.,2009
3. The dynamics of large-scale cyclogenesis over the North Pacific;Black, R. X.,1993
4. Horizontal structure of 500 mb height fluctuations with long, intermediate and short time scales;Blackmon, M. L.,1984a
5. Time variation of 500 mb height fluctuations with long, intermediate and short time scales as deduced from lag-correlation statistics;Blackmon, M. L.,1984b