# S-values

From AMS Glossary

## S-values

Specific temperature anomalies given by the relation where

*T*is the actual temperature and*T*_{p}is the standard-atmosphere temperature at a point where the pressure altitude is*z*_{p}.S-values are usually expressed in terms of tenths of degrees per hundred degrees absolute temperature. S-value lines are drawn on 4D charts because they are related to D-values by where Δ

_{v}*D*is the variation in D-value for a given Δ*z*_{p}variation in pressure altitude.