500 hPa height , surface pressure 2011 Feb 1 12Z Smaller scale features less evident in middle/upper troposphere

850 hPa , 2006 Feb 04-06 Feb 05 Feb 06 Feb 04 Svnoptic scale cyclones can develop rapidly (1-2 d.) and move generally eastward

02/02/2009 sfc 500 hPa Upper level trough westward of surface frontal low pressure

Feb 2 1200Z Feb 3 1200Z

Feb 2 1200Z Feb 4 1200Z

Jan 500 hPa climatology Quasi-stationary planetary-scale waves

Jan 850/500/300 hPa climatology little if any phase shift with height (in the troposphere)

Observed zonal mean u, T DJF JJA

Observed zonal mean u, T DJF tropopause JJA

Observed zonal mean u, T DJF JJA cold winter polar stratosphere high, cold, tropical tropopause JJA very flat T contours in tropics

Observed zonal mean u, T DJF main tropospheric (subtropical) jets JJA

Observed zonal mean u, T DJF JJA midlatitude surface westerlies tropical easterlies

Observed zonal mean u, T DJF JJA polar night jets in winter stratosphere JJA summertime stratospheric easterlies

Mean meridional circulation DJF V ~ 1 m/s

Mean meridional circulation DJF Hadley cells Ferrell cells

Seasonal variation of the Hadley circulation

Different averaging approaches (Townsend & Johnson, JAS, 1985) mass streamfunction Average at fixed p Average at fixed θ