Steven M. Cavallo |
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Tropopause polar vortex (TPV) Real-time composites
Using data from the WRF real-time simulations over the Canadian Arctic, composites of various fields are given below.
The tropopause is taken here to be the 2 PVU surface. Vortices are found by searching for minima in tropopause potential temperature
over the domain, then searching outward for a reversal in the tropopause potential temperature gradient. If this is not found in each direction,
then the minimum is not regarded to be associated with a vortex. Further, the minimum value must be at least two standard deviations lower than the domain mean value.
The vortex core is regarded as the minimum tropopause potential temperature in a vortex.
Dates for the composites begin on August 2, 2007 through the current date.
Horizontal sections
Below are composites of tropopause potential temperature, and 500 hPa geopotential heights, averaged horizontally with
respect to the vortex core.
Cross sections
Horizontal averaging is relative to the vortex core (determined by the location of lowest tropopause potential temperature),
while vertical averaging is relative to the ground.
The first column shows the fields relative to the vortex core, the second column shows the fields relative to a fixed location
near the center of the domain which we call the background state, and the third column shows the anomalies (vortex relative - background).
The bold black contour in each of the plots is the tropopause, which we take to be the 2 PVU surface.
Composite (East-west) cross sections in Canadian Arctic |
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Vortex relative |
Fixed location (background state) |
Vortex - background |
| Ertel potential vorticity (EPV) |
X |
X |
X |
| Wind magnitude |
X |
X |
X |
| Vertical motion (omega) |
X |
X |
X |
| Relative humidity |
X |
X |
X |
| Cloud water + ice mixing ratios |
X |
X |
X |
| EPV tendency from all diabatic effects |
X |
X |
X |
| EPV tendency from radiation |
X |
X |
X |
| EPV tendency from latent heating |
X |
X |
X |
| EPV tendency from boundary layer and other mixing processes |
X |
X |
X |
| Number of samples |
X |
X |
X |
Further information: |
| Cavallo, S.M. and G.J. Hakim, 2008: Analysis and structure of a tropopause cyclone.
Monthly Weather Review, submitted. |
| Hakim, G.J. and A. K. Canavan, 2005: Observed Cyclone-Anticyclone Tropopause Asymmetries.
J. Atmos. Sci., 62 (1), 231-240. |
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