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 fundamental lines which are used to describe various processes in the atmosphere. These lines include:

Isobars - lines of constant pressure
Isotherms - lines of constant temperature
Dry adiabats - related to dry adiabatic processes (potential temperature constant)
Saturated adiabats - which are related to saturated adiabatic processes (wet bulb potential temperature constant).

On the tephigram there are two kinds of information represented:

The environment curves (blue) which describes the structure of the atmosphere

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

In addition, the right hand panel displays height, wind direction, speed and a selection of pressure levels.

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