Bulk Richardson Number #628
Description
Add a calculation for the Bulk Richardson Number with comparison to GEMPAK.
From Wikipedia (cite Stull or Garratt)
Below is the formula for the BRN. Where g is gravitational acceleration, Tv is
absolute virtual temperature, Δθv is the virtual potential temperature
difference across a layer of thickness Δz (vertical depth), and ΔU
and ΔV are the changes in horizontal wind components across
that same layer.
