In a physical (and especially geophysical) simulation context, a diagnostic equation (or diagnostic model) is an equation (or model) that links the values of these variables simultaneously, either because the equation (or model) is time-independent, or because the variables all refer to the values they have at the identical time. This is by opposition to a
prognostic equation Prognostic equation - in the context of physical (and especially geophysical) simulation, a prognostic equation predicts the value of variables for some time in the future on the basis of the values at the current or previous times.
For instance, ...
.
For instance, the so-called
ideal gas law
The ideal gas law, also called the general gas equation, is the equation of state of a hypothetical ideal gas. It is a good approximation of the behavior of many gases under many conditions, although it has several limitations. It was first stat ...
(''PV'' = ''nRT'') of classical
thermodynamics
Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of th ...
relates the
state variable
A state variable is one of the set of variables that are used to describe the mathematical "state" of a dynamical system. Intuitively, the state of a system describes enough about the system to determine its future behaviour in the absence of a ...
s of that gas, all estimated at the same time. It is understood that the values of any one of these variables can change in time, but the relation between these variables will remain valid at each and every particular instant, which implies that one variable cannot change its value without the value of another variable also being affected.
References
* James R. Holton (2004) ''An Introduction to Dynamic Meteorology'', Academic Press, International Geophysics Series Volume 88, Fourth Edition, 535 p., , .
External links
Amsglossary.allenpress.com
{{DEFAULTSORT:Diagnostic Equation
Atmospheric dynamics