Key Parameters

  • Height contours at 500 and 1000 hPa:
    • Surface and mid level height contours: similar appearance to a CF (see Cold Front ), no separate pressure minimum or deepening trough, normally associated with a "classical" Wave (see Wave )
  • Height contours at 300 hPa:
    • Significantly sharp and deepening trough to the rear of the cloud band
  • Vorticity Advection at 300 hPa:
    • Distinct maximum caused by the advection of shear and curvature vorticity
    • Also resulting from sharp trough to the rear
    • Distinct advection of curvature vorticity through the stream field
  • Shear and Curvature Vorticity at 300 hPa:
    • Isolines of Curvature Vorticity cross the cloud band at the Wave point at an acute or nearly right angle
    • Shear vorticity: as in Cold Fronts, associated with a strong jet
  • Isotachs and Shear - Zero - Line at 300 hPa:
    • Position of the Wave bulge relative to the Isotachs depends on the stage in its life cycle: during the initial stage the Upper Wave forms at the entrance region of the jet, later the Upper Wave bulge propagates towards the exit region
    • The majority of Upper Waves studied show an extension of the cloud bulge into the side of cyclonic shear
  • Potential Vorticity:
    • Tropopause folding to the rear of the cloud band upwind of the Wave bulge (PV anomaly)
    • PV=1 has protruded downward to about 500 to 400 hPa during the initial stage
    • PV anomaly slightly weakening during life cycle (no further development of Upper Wave)
  • Temperature Advection at 700 hPa:
    • Cold Advection is associated with the Upper Wave during the whole life cycle

Height contours at 1000 and 500 hPa

22 August 2005/12.00 UTC - Meteosat 8 IR 10.8 image; cyan: height contours 500 hPa, magenta: height contours 1000 hPa

 

Height contours at 300 hPa and PVA 300 hPa

22 August 2005/12.00 UTC - Meteosat 8 IR 10.8 image; green: height contours 300 hPa, red: positive vorticity advection (PVA) 300 hPa

 

Shear and Curvature Vorticity at 300 hPa

22 August 2005/12.00 UTC - Meteosat 8 IR 10.8 image; blue: shear vorticity 300 hPa, brown: curvature vorticity 300 hPa

 

Isotachs and Shear - Zero - Line at 300 hPa

22 August 2005/12.00 UTC - Meteosat 8 IR 10.8 image; black: zero line of shear vorticity 300 hPa, yellow: isotachs 300 hPa

 

Potential Vorticity and TA 700

22 August 2005/12.00 UTC - Meteosat 8 IR 10.8 image; magenta: potential vorticity, red: temperature advection 700 hPa

 

Distinction between Wave and Upper Wave according to the key parameters


Most parameters show similar distribution and characteristics, except:

Upper Wave Wave
No separate trough or minimum at surface Distinct short Wave trough or minimum at surface
Sharp pronounced trough at upper levels Trough at upper levels similar to fronts
CA at 700 hPa Distinct WA maximum at 700 hPa
Higher numerical values of curvature vorticity at upper levels (300 hPa) Higher numerical values of curvature vorticity at lower levels (700 hPa)

The set of IR images below show the differences described in the above table. Below left is the case of an Upper Wave, below right the case of a Wave. While the Upper Wave has no separate surface trough superimposed, the Wave case from 4 July 2005 shows a distinct surface low as well as maximum of warm advection superimposed upon the Wave bulge.


22 August 2005/12.00 UTC - Meteosat 8 IR 10.8 image; red: temperature advection 700 hPa, magenta: height contours 1000 hPa
04 July 2005/12.00 UTC - Meteosat 8 IR 10.8 image; red: temperature advection 700 hPa, magenta: height contours 1000 hPa