Interannual and interdecadal variability in United States surface-air temperatures, 1910-87 |
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| Authors: | Michael D Dettinger Michael Ghil Christian L Keppenne |
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| Institution: | (1) U.S. Geological Survey, 92123-1135 San Diego, California, USA;(2) Department of Atmospheric Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California, USA;(3) Department of Atmospheric Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California, USA;(4) Jet Propulsion Laboratory, California Institute of Technology/NASA, 91109 Pasadena, California, USA |
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| Abstract: | Monthly mean surface-air temperatures at 870 sites in the contiguous United States were analyzed for interannual and interdecadal variability over the time interval 1910-87. The temperatures were analyzed spatially by empirical-orthogonal-function analysis and temporally by singularspectrum analysis (SSA). The dominant modes of spatio-temporal variability are trends and nonperiodic variations with time scales longer than 15 years, decadal-scale oscillations with periods of roughly 7 and 10 years, and interannual oscillations of 2.2 and 3.3 years. Together, these modes contribute about 18% of the slower-than-annual United States temperature variance. Two leading components roughly capture the mean hemispheric temperature trend and represent a long-term warming, largest in the southwest, accompanied by cooling of the domain's southeastern quadrant. The extremes of the 2.2-year interannual oscillation characterize temperature differences between the Northeastern and Southwestern States, whereas the 3.3-year cycle is present mostly in the Western States. The 7- to 10-year oscillations are much less regular and persistent than the interannual oscillations and characterize temperature differences between the western and interior sectors of the United States. These continental- or regional-scale temperature variations may be related to climatic variations with similar periodicities, either global or centered in other regions; such variations include quasi-biennial oscillations over the tropical Pacific or North Atlantic and quasi-triennial oscillations of North Pacific sea-surface temperatures.The U.S. Government right to retain a non-exclusive, royalty-free licence in and to any copyright is acknowledged. |
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