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Valentia Tephigram

Notes on Tephigram

A tephigram is a graphical representation of observations of pressure, temperature and humidity made in a vertical sounding of the atmosphere. Vertical soundings are made using an instrument called a radiosonde, which contains pressure, temperature and humidity sensors and which is launched into the atmosphere attached to a balloon.

The tephigram contains a set of process curves which are used to describe various processes in the atmosphere. These lines include:

  • Isobars – lines of constant pressure (horizontal slightly curving, grey)
  • Isotherms – lines of constant temperature (sloping left-right, orange with 0C in Blue)
  • Dry adiabats – related to dry adiabatic processes (potential temperature constant, sloped right-left, Purple)
  • Saturated adiabats – related to saturated adiabatic processes (wet bulb potential temperature constant, curved, green)
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    On the tephigram there are two kinds of information represented:

    The environment curves which describes the structure of the atmosphere. These are Temperature (Red) and Dew Point (Green)

    The process curves which describes what happens to a parcel of air undergoing a particular type of process. (eg. Adiabatic process).

    In addition, on the right hand side are wind direction and speed and heights at the standard levels. Wind is shown in wind-arrow format with the head of the pointing to where the wind is going and the strength given by the feathers – a long feather is 10kts, a short feather 5knots and a triangle 50kts. Add the feathers to get the speed.

    Tephigrams can be used by the forecaster for the following purposes:

    – to determine moisture levels in the atmosphere
    – cloud heights
    – to predict levels of convective activity in the atmosphere
    – forecast maximum and minimum temperatures
    – forecast fog formation and fog clearance
    – detect the presence and height of inversions

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