Valentia Observatory 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
Saturated adiabats -
which are related to saturated adiabatic processes (wet bulb potential
temperature constant). (curved, green)
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