nomogram

=Nomogram=

toc Read about a cartesian coordinate graph that uses logarithms and transcodes data between scales.

=Overview= A nomogram is a diagram that can be used to graphically perform a certain calculation. =Atmospheric nomogram= A nomogram is a sheet of paper with graduated scales (for example for temperature, pressure, and potential temperature). We then put a ruler over the nomogram crossing the temperature scale at the given temperature value and the pressure scale at the given pressure value. Where the ruler crosses the potential temperature scale the potential temperature value can be read off. Of course this process can be generalized: given potential temperature and pressure we can read off the corresponding temperature. In this sense a nomogram is quite flexible. The nomogram contains four graduated scales: for potential temperature, density, pressure, and temperature. We can choose any two of these and read off the other two using the ruler. But there is more: the temperature scale also shows a saturated vapour pressure scale, and the pressure scale also shows a 1976 US standard atmosphere height scale, so these two quantities can be thrown in the mix as well. For good measure I included a Celcius-Fahrenheit converter, which consists of a seperate linear scale with two graduations, the simplest form of nomogram possible.

Atmospheric Nomograph by M H P Ambaum, University Of Reading, UK.