Unit conversions required for some spatial plots

[daflack]

Some of the spatial plots are in non-standard units. Therefore, for ease of interpretation we need to convert these before plotting, and then update the colorbars accordingly.

[jfrost-mo]

Part of the fun here is that some plots will want to convert the same variable to different units. For example, temperature often wants to be in Celsius, but sometimes should be left in kelvin.