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Explanation of this kind of diagram, that we use for illustrating the sounding data


All soundings, provided by DreiTageWetter, are type of skew-T log-P diagram. Air temperature is the red line and the blue line in the diagram is the dew point.

The skew-T log-P diagram:

The skew-T log-P diagram has special features, that are explained in the following:

  • The x-axis (abscissa) indicates the temperature (°C). But there is a special feature: The lines of equal temperature (isothermes) are not parallel to the x-axis! They are skewed and run from bottom left to top right with an angle of 45°. This is important for reading out temperatures.
  • The y-axis (ordinate) indicates the pressure (hPa). The special feature of this axis: It is a logarithmic scale ranging between 100 and 1050 hPa.

In addition to the two main features there exist further axes in the diagram:

  • Dry adiabats: They run from bottom right to top left and become steeper with increasing height (decreasing pressure!). The dry adiabats are dashed lines in our diagram.
  • Wet adiabats: In our diagram they are solid lines, that are steeper than the dry adiabats at lower altitudes. At higher altitudes their behavior is more and more like the dry adiabats.
  • Lines of saturation mixing ratio: They are straight lines running from bottom left to top right. In our case they are dashed as well.

On the right hand side of the diagram you will find symbols, that indicate wind direction and wind speed for different altitudes. A long dash implies a wind speed of 10 knots and a short dash indicates a wind speed of 5 knots. A triangle marks a wind speed of 50 knots. One knot (kn) is 1.852 km/h.

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