Propagation of planetary-scale zonal mean wind anomalies and polar oscillations

Weihong Qian,Haoyuan Liang

doi:10.1007/s11434-012-5168-1

Abstract

Global atmospheric variables can be physically decomposed into four components: (1) the zonal time averaged climate symmetric component, (2) the time averaged climate asymmetric, (3) the zonal-mean transient symmetric anomaly, and (4) the transient asymmetric anomaly. This study analyzes the relationships between the intra-seasonal and inter-annual variability of planetary scale decomposed zonal and meridional winds in the tropopause, and oscillations such as those from the El Nino-Southern Oscillation (ENSO), the Arctic Oscillation (AO) and the Antarctic Oscillation (AAO). The tropical inter-annual zonal mean wind anomalies in the tropopause are linked with the ENSO cycle and can propagate into the subtropics, mid-latitudes, and polar front regions via abnormal meridional vertical cells. Similarly, tropical intra-seasonal (40–60-d) zonal wind anomalies can reach the subtropics and mid-latitudes. The polar intra-seasonal zonal wind anomalies in the tropopause can propagate toward high-latitude areas. Thus, the AO and the AAO are the result of the interaction and propagation of these planetary scale zonal wind anomalies.

Highlights

Global atmospheric variables can be physically decomposed into four components: (1) the zonal time averaged climate symmetric component, (2) the time averaged climate asymmetric, (3) the zonal-mean transient symmetric anomaly, and (4) the transient asymmetric anomaly
It is commonly believed that extreme weather or abnormal climate events are both affected by equatorial El Niño events, and extreme events are closely linked with the Arctic Oscillation (AO), Antarctic Oscillation (AAO), MJO and other atmospheric oscillations
A maximum center of standard deviation (0.77 m/s) of the daily zonal-mean meridional wind anomalies appears near the equatorial tropopause (150 hPa), and decreases to 300 hPa at the two poles

Summary

Results

The planetary-scale zonal-mean transient symmetrical wind anomalies component is calculated using eq (1). A maximum center of standard deviation (0.77 m/s) of the daily zonal-mean meridional wind anomalies appears near the equatorial tropopause (150 hPa), and decreases to 300 hPa at the two poles. If monthly mean instead of daily meridional wind anomalies were used, the distribution of monthly standard deviations is similar to Figure 1(a), but the value at the equatorial tropopause is only 0.45 m/s. The standard deviations calculated by daily and monthly planetary scale mean zonal wind anomalies have a similar distribution. 2 4 4 4 4 4 2 wind, and sometimes are not observed when might be expected, e.g. 2009 to 2010

Meridional propagation of zonal wind anomalies

Causes of zonal-mean zonal wind anomalies

Conclusion