The East Pacific Wavetrain: Its variability and impact on the atmospheric circulation in the boreal winter |
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Authors: | ZHOU Putian SUO Lingling YUAN Jiacan TAN Benkui |
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Institution: | Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871,Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, Nansen Environmental and Remote Sensing Center, Bergen, Norway, Bjerknes Center for Climate Research, Bergen, Norway,Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871,Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871 |
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Abstract: | The East Pacific wavetrain (EPW) refers to here the intense stationary wave
activity detected in the troposphere over the East Pacific and North America
in 45 northern winters from 1958 to 2002. The EPW is generated in the lower
troposphere over the East Pacific, propagating predominantly eastward into
North America and slightly upward then eventually into the stratosphere. The
intensity of the EPW varies from year to year and exhibits apparent decadal
variability. For the period 1958--1964, the EPW was in its second maximum,
and it was weakest for the period 1965--1975, then it was strongest for the
period 1976--1987. After 1987, the EPW weakened again.
The intensity and position of the members (i.e., the Aleutian low, the North
American trough, and the North American ridge) of the EPW oscillate from
time to time. For an active EPW versus a weak EPW, the Aleutian low deepens
abnormally and shifts its center from the west to the east of the date line,
in the middle and upper troposphere the East Asian trough extends eastward,
and the Canadian ridge intensifies at the same time. The opposite is true
for a weak EPW. Even in the lower stratosphere, significant changes in the
stationary wave pattern are also observed.
Interestingly the spatial variability of the EPW assumes a Pacific--North
American (PNA)-like teleconnection pattern. It is likely that the PNA
low-frequency oscillation is a reflection of the oscillations of intensity
and position of the members of the EPW in horizontal direction. |
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Keywords: | East Pacific wavetrain stationary waves vertical propagation |
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