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The East Pacific Wavetrain:Its Variability and Impact on the Atmospheric Circulation in the Boreal Winter

Advances in Atmospheric Sciences 2012年第3期29卷 471-483页

作者：周普天所玲玲袁嘉灿谭本馗 Department of Atmospheric and Oceanic Sciences School of Physics Peking University Nansen Environmental and Remote Sensing Center BergenNorway Bjerknes Center for Climate Research BergenNorway

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 telecon- nection 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.

关键词： East Pacific wavetrain stationary waves vertical propagation

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Analysis of stationary-Wave Nonstationarity in the Northern Hemisphere 500-hPa Height Field

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Acta meteorologica Sinica 2010年第3期24卷 287-296页

作者：周国华王盘兴施宁李巧萍佘高杰 Institute of Atmospheric Sciences Nanjing University of Information Science & Technology National Climate Center China Meteorological AdministrationBeijing 100081

In this paper,the concept of stationary-wave nonstationarity is presented and elucidated in the framework of the Lorenz circulation *** concept indicates the relative magnitude of the zonal nonuniform abnormity to the intensity of stationary waves on the monthly mean *** on the Lorenz circulation decomposition,the nonstationarity degree I_（us）（I_（us）~1） of the global（local） stationary waves is defined,and then used to analyze the stationary-wave nonstationarity at 30°-60°N,where the intensity of stationary waves at 500 hPa in the Northern Hemisphere,as is well known,is very *** following findings are obtained：（1） There exist seasonal southward and northward movements in the position of the nonstationarity zones of the global stationary *** steady stationary waves occur in midlatitudes （35°-55°N） in winter and in the subtropical region（south of 35°N） in summer,associated with the major troughs over East Asia and North America and the weak European trough in winter,and with the relatively steady subtropical high system in summer.A high value center of I_（us） is at 35°N in spring and 50°N in summer,which might be caused by the seasonal variation of stationary-wave intensity,particularly in association with the interannual variability of trough/ridge positions of stationary waves on the monthly mean maps.（2） There exists obvious asymmetry in I_（us）~1,with the steady zones always located in the areas controlled by strong troughs/ridges and the unsteady ones in the areas where the stationary-wave intensity is *** I_（us）~1 in the subtropics（south of 35°N） is larger in winter than in summer,and vice versa in the midlatitude region（north of 35°N）.The summertime distribution of I_（us）~1 on the whole shows a rather complicated ***,North Europe is the most unsteady area for local stationary waves,as represented by high values of I_（us）~1 in both summer and winter,while over the North American continent （about 120°E-60°W）,the I

关键词： 500-hPa geopotential height field stationary waves nonstationarity general circulation system

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