Package Design Document

Thermo Design Document


People need to use equations to calculate thermodynamic quantities all the time. There should be a nice interface to do this.


  • Easy to use interface that minimizes how much you need to memorizes
  • Works on xarray dataarrays
    • Takes full advantage of labeled data and automated broadcasting (e.g. for latitude-dependent calculation of absolute salinity)
  • Handles units – where present in metadata or passed in by user as keyword
  • Can work for atmosphere or ocean (or arbitrary set of equations)
  • Scales to big data
  • Can take advantage of metadata stored in DataArrays
  • Clear in documentation which form of equations are being solved
  • Support for custom equation of state (particularly for ocean)
  • What does it calculate?
    • Atmosphere
      • Potential temperature
      • saturation vapor pressure
      • Slope of adiabats in T-P space etc
      • etc
    • Ocean
      • Density
      • Slope of isopycnals in T-S space
      • etc
    • All functions of thermodynamic state variables


  • Isolate solving code into a new package, that gets used by the atmos package
  • Someone can make an ocean package that does something similar to the atmos package, containing equations for ocean thermodynamics
  • Have saturation vapor pressure assumption treated specially as keyword argument
  • Chain numba calls when doing ocean eqns, they’re huge!
  • Aim for pure Python / numba implementation

What are people doing now?

  • Ocean
    • GSW
    • Seawater toolkit (depractated but still widely used)
    • Or using routines extraced from models
    • No one rolls their own (formulas too clunky)
  • Atmosphere
  • Don’t have a package that can use labeled xarray data effectively

link to hackpad