RFM Driver Table Sections

*ATM Section: Atmospheric Profiles

07JUL17

Type
Primary Section#5

Description
Atmospheric profile data.

Format
Multiple fields, order is significant.
FieldTypeDescription
FILATM C*200 Name of an .atm file

With the GRA Flag enabled, ie two-dimensional atmosphere, it is necessary to append a pair of brackets (...) containing an angle (no spaces) directly after each FILATM field to specify the horizontal location of the profile (RFM v4.33 onwards: PSI qualifier is optional, assume PSI=0.0 if omitted)
QualifierTypeDescriptionRange
(PSI) R*4 Horizontal angle [deg] -90:+90

Notes
  1. The order of filenames is significant since the altitude (*HGT) grid of the first file defines the internal altitude profile of the RFM, with the first (lowest) grid point, not necessarily 0km, defining the surface altitude and the last (highest) grid point defining the top of the atmosphere. For profiles other than *HGT, previous values will be overwritten if the same profile type appears in a later file.
    RFM v5: the first profile in the first file could also be pressure (*PRE), and then ln(p) is used as the internal vertical coordinate rather than height
  2. If subsequent .atm files include profiles specified over smaller altitude ranges than the first file the end values of the short profiles are duplicated, i.e., the short profiles are extended over the full height range assuming the end values remain constant (except for pressure, which is extrapolated in log space from the pair of end values).
  3. Extra profile levels may be added by the JAC, LAY, LEV or OBS Flags.
  4. The PRF Flag can be used to write out the actual profile that ends up being used in the RFM.
  5. Angles PSI are defined as subtended at the local centre of curvature, which is approximately the same as the spacing of degrees of latitude, i.e., PSI=1 corresponds to a distance of around 111 km on the surface of the earth. Direction is defined so that the observer is at high values looking towards low values, i.e. so that profiles with lower values of PSI are further away. Tolerance for distinguishing different PSI angles (fixed by PSITOL parameter in prfgra.for) is 1E-3 deg, approximately 100m along the surface. [simple geometry also tells you that any variation in elevation angle of the observation will also move the tangent point location, PSI, by the same angle]
  6. Absolute PSI values are defined in one of two ways, depending on whether the OBS flag enabled
    • OBS flag enabled (usual case): PSI values are defined relative to the observer location PSIOBS in the *OBS section.
    • OBS flag disabled: PSI=0 is defined as the location of all the tangent points either refracted or geometric according to the specification of the *TAN section.
  7. When the GRA Flag is enabled, a two dimensional atmosphere is established so that profiles are written (or overwritten) at each location PSI independently, sharing only the height grid established by the first .atm file in the *ATM section. However, it is not necessary to supply profiles for all absorbers at all locations since, after all profiles have been read, there is an interpolation step to fill in any missing profiles from those that have been supplied. Suggested use is that the atmosphere is fully defined for PSI=0, and only the horizontally varying profiles are supplied at other locations.
  8. If no profile is explicitly supplied at PSI=0, then a reference profile at PSI=0 is created by interpolating the supplied profiles.
  9. T, lnp, and ln(VMR) (or VMR if LIN Flag enabled) are assumed to vary linearly at each altitude surface between supplied locations, and to remain constant outside the range of supplied locations. (RFM v5, using pressure grid, then T, z, ln(VMR) are assumed to vary linearly with ln(p) )
  10. Isotopes: if isotopes are specified in any input files (eg by having *CH4(1) as one of the profiles) then the RFM treats these as separate gases - one gas for each specified isotopic profile plus one gas for the remaining isotopes (even if profiles have been supplied for all isotopes). Any subsequent profiles for just *CH4 will not overwrite the isotopic profile.
  11. The header record of each accepted profile, plus *END markers, are written to the rfm.runlog file, together with notification if this replaces an existing profile.
  12. After all .atm files are read, there is a check that profiles of Temperature, Pressure and VMR for absorber specified in the *GAS section have been found (& extinction profile for aerosol), otherwise a fatal error message results.
  13. RFM v5.0: a pressure profile is always required but, with a pressure grid, altitude is only required for limb-viewing calculations, if the HYD flag is used, or to identify levels for perturbations (JAC flag) or output levels (LEV or FLX flags).

Examples
One-dimensional atmosphere
*ATM                
     hgtgrd.atm     ! Define altitude grid for calculation (z only)
     std.atm        ! US Std Atmosphere (z,p,T,H2O,CO2,O3,N2O,CO,CH4,O2)
     minor.atm      ! Minor species (HNO3, etc)
     co2_2005.atm   ! Replace US Std. CO2 vmrs with 2005 concentrations
Two-dimensional atmosphere, defined at 3 locations
*ATM
     std.atm(0)     ! US Std Atm, all species, at PSI=0 
     t_near.atm(2)  ! "near" side temperature profile at PSI=2 deg
     p_near.atm(2)  ! Pressure profile, also at PSI=2 deg
     t_far.atm(-1)  ! "far" side temperature profile, at PSI=-1 deg
     minor.atm(2)   ! Minor species, initially placed at PSI=2
                    ! All std and minor species apart from p,T will be 
                    ! duplicated at PSI=-1, 0 and +2. 
                    ! The std p profile at PSI=0 will be duplicated at PSI=-1

Bugs
Bug#109 (Fixed v4.34)
Bug#82 (Fixed v4.31)
Bug#81 (Fixed v4.29)
Bug#21 (Fixed v4.11)
Bug#19 (Fixed v4.11)