Atlas
Variables
Having selected a storm and time offset, there are a number of
variables which can be plotted. Most of the
variables are stored on a number of pressure surfaces from 925 hPa at
the ground up to 200 hPa. However, the winds can be plotted on
Θ surfaces (surfaces of constant potential temperature), and the
surface pressure and cloud cover are all only at one pressure surface.
The variables can be selected from the list below or from the buttons
on the left hand side:
- Cloud cover: cloud cover at three
levels, low, medium and high. Let sigma = Pressure / Surface pressure. Low cloud cover is for 1.0 > sigma > 0.8, medium cloud cover is for 0.8 >= sigma > 0.45 and high cloud cover is for 0.45 >= sigma
- Divergence: divergence on pressure
surfaces
- Geopotential: geopotenial on pressure
surfaces.
- Mean sea level pressure: the pressure at
mean sea level
- Pressure (Θ surfaces):
pressure on Θ surfaces
- Relative humidity: relative humidity on
pressure surfaces
- Relative vorticity: relative vorticity
on pressure surfaces
- Temperature: temperature on pressure
surfaces
- Θe: equivalent
potential temperature on pressure surfaces
- Vertical velocity: vertical
velocity on pressure surfaces
- Wind - absolute:
the absolute wind speed on both pressure and Θ surfaces
- Wind - system relative: the
system relative wind (or wind speed in the frame of reference of
the storm) on both pressure and Θ surfaces