RFM Flags

HYD Flag

03AUG22

Enabled
Calculate Curtis-Godson parameters for plane-parallel atmosphere using height spacing (from *HGT profile) to infer g.M (gravity x molecular mass of air) in converting VMR to absorber amount (basically allow unhydrostatic atmospheres — I'm aware that the name of the flag is misleading!)

Disabled
Create Curtis-Godson parameters for plane-parallel atmosphere using only pressure level information, with GRAVTY and WGTAIR from phyadj_dat.f90 (ie assuming hydrostatic equilibrium).

Restrictions
Requires either NAD or ZEN flags to be enabled.

Notes
  1. For plane-parallel atmospheres (NAD or ZEN flags), the Curtis-Godson equivalent p,T and partial pressure for each path can be expressed as explicit functions of the profile values (see notes at the top of module vrtsum_sub.f90). However to calculate the absorber amount in each layer requires a factor g.M where g=gravity, M=molar weight of air.
  2. The RFM default is to use internal values of g=GRAVTY and M=WGTAIR (see *PHY for how to adjust these from their default values), which makes the plane parallel atmosphere calculations completely independent of the altitude grid
  3. With the HYD flag the internal values GRAVTY and WGTAIR are ignored and the product g.M is inferred from the altitude grid spacing assuming hydrostatic equilibrium.

Bugs
None reported