Tephigram

takes its name from Temperature and Entropy (formerly noted by the greek letter 'phi'). Used in the UK Met.Office to plot upper air soundings, and assess such as instability, depth of moisture/cloud layers, fog points, temperature of free convection, condensation level etc. Designed by Napier Shaw early in the twentieth century. Other thermodynamic diagrams are used by other services (e.g. the pseudoadiabatic or Stüve chart [ common on sites ]; skewT/log(p) diagram: ( see also the entry for Thermodynamic diagrams. )