.pth File

RFM File Formats: Ray Path Diagnostics

11JUN24

Type
Output(s), if PTH Flag enabled.

Description
Ray tracing and Curtis-Godson integration diagnostics

Filename(s)
Default is pth_[t].asc where [t] is the ray path as defined in the *TAN section.
Different names may be specified in the *OUT section of the Driver Table.

Structure
The file is a set of fixed-structure records, with additional records for Limb-viewing and Limb-viewing with a 2D atmosphere.
File Structure
!HEADER1 Header Record
!HEADER2 Header Record
! Rfr.Tan Geo.Tan Tan.Zen Tan.Psi Rad.Crv Obs.Ele Obs.Alt Obs.Psi Header Record
!   RFRTAN     GEOTAN   ZENTAN   [PSITAN]   RADCRV   [ELEOBS]  [ALTOBS]  [PSIOBS] Limb Geometry
NGAS NSEG1 NSEG2 = NGas, NSeg1, NSeg2 Array dimensions
For iGas = 1, NGas:
  GAS(iGas) Molecule
  !HEADER4 Header Record
  For i = 1, NSeg1:
    LEV(i) ALT(i) ANG(i) PRE(i) TEM(i) VMR(i) AMT(i) LEN(i) FLG(i) Path segment data
Total: TOTAMT TOTLEN            Totals
  For i = 1, NSeg2:
    LEV(i) ALT(i) ANG(i) PRE(i) TEM(i) VMR(i) AMT(i) LEN(i) FLG(i) Path segment data
Total: TOTAMT TOTLEN            Totals
[eof]

Fields
FieldTypeDescription Units Range
!HEADER1 C80 Ray path identification and RFM version
!HEADER2 C80 Text from *HDR section of Driver Table
RFRTAN F9.3 Refracted Tangent Height km ≥ 0
GEOTAN F10.3 Geometric Tangent Height km
ZENTAN F10.3 Zenith Angle at Tangent Pt deg 0 – 90
PSITAN F10.3 Line-of-Sight Angle at Tangent Pt (if GRA flag else blank) deg ±180
RADCRV F10.3 Radius of Curvature km
ELEOBS F10.3 Observer Elevation Angle deg
ALTOBS F10.3 Observer Altitude km
PSIOBS F10.3 Observer LOS Angle deg
NGAS I No.of different molecules
NSEG1 I No.of path segments for ray on downward path
NSEG2 I No.of path segments for ray on upward path
GAS C7 Name of molecule, eg h2o
!HEADER4 C80 Text column headers for next record
LEV I Atmospheric Profile Layer# same for all molecules
ALT R Altitude [km] of segment lower boundary same for all molecules
ANG R Zenith or (GRA Flag) LOS angle [deg] Edge of seg nearest obs.
PRE R Curtis-Godson Pressure [mb]
TEM R Curtis-Godson Temperature [K]
VMR R Volume Mixing Ratio [ppv]
AMT R Absorber Amount [kmol/cm2]
LEN R Path Length [km] same for all molecules
FLG I Flag 1=explicitly calculuated, 0=scaled
TOTAMT R Total Amount in path [kmol/cm2]
TOTLEN R Total Length of path [km] same for all molecules
Type: I=Integer; R=Real; D=Double Precision; Cn=character string, length n.

Notes
  1. There is an IDL Procedure [read_pth.pro] which may help understand how to read these files.
  2. !HEADER3 and the following record are only generated for limb-viewing mode, ie not with HOM NAD or ZEN Flags.
  3. ! RFRTAN ... the record starts with an exclamation mark, ie notionally a comment record since its contents are not required to read the rest of the file. The RFRTAN field is written with F9.3 but the other fields are all written F10.3 (so a particular field occupies the same 10-character position whatever options have been used).
  4. ZENTAN is 90 for a 'true' tangent point, but if the ray intersects the surface or for an upward-viewing limb observation then the angle between the ray and the local vertical (<90) is given instead
  5. PSITAN is left blank unless the GRA Flag is enabled, ELEOBS and ALTOBS are left blank unless the OBS Flag is enabled, and PSIOBS is left blank unless both the GRA and OBS Flags are enabled.
  6. NSEG1,NSEG2: the ray-tracing starts at the observer and proceeds away through the atmosphere downwards first, then upwards, although either the upwards or downwards components may be absent for particular viewing geometries. If the atmosphere is horizontally homogeneous (ie unless the GRA Flag is enabled) the ray-tracing diagnostics are only listed for one of the two parts of the path (whichever spans most atmospheric layers).
  7. Note that while ALT is defined for the lower of the two segment boudaries, ANG is defined for the edge furthest from the observer, so, for a given atmospheric level LEV, the two ALT values will be the same while the two ANG values will be different.
  8. Enabling the CLC Flag will result in all FLG values being set to 1
  9. TOTAMT and TOTLEN refer only to the part of the path listed above, ie represent an addition of all the column entries.

Examples
Nadir viewing, co2 and o3
! Path diagnostics calculated for AirMass=1.00           by RFM v.5.02_10FEB    
!04MAY17 RFM LIN flag test                                                      
           1          21           0  = NGas, NSeg1, NSeg2
h2o      
Lev  Zlow[km]  Zen[dg] Temp[K]  Press[mb]  VMR[ppv]   Amt[kmol/cm2] Len.[km] Clc
  1    0.000  180.000  278.601 8.85143E+02 8.83231E-03 8.85801E-05     3.000  0
  2    3.000  180.000  261.300 6.06299E+02 2.92209E-03 2.12875E-05     3.000  0
  3    6.000  180.000  242.600 4.06162E+02 9.53139E-04 4.87718E-06     3.000  0
  4    9.000  180.000  226.350 2.68513E+02 2.48548E-04 7.69385E-07     3.000  0
  5   12.000  180.000  217.673 1.65506E+02 1.01144E-05 2.30978E-08     3.000  0
  6   15.000  180.000  215.792 9.88789E+01 3.83114E-06 6.22619E-09     3.000  0
  7   18.000  180.000  216.638 6.16268E+01 4.18995E-06 4.22633E-09     3.000  0
  8   21.000  180.000  218.356 3.86233E+01 4.57746E-06 2.86345E-09     3.000  0
  9   24.000  180.000  220.793 2.43213E+01 4.83690E-06 1.87871E-09     3.000  0
 10   27.000  180.000  224.647 1.53859E+01 5.05903E-06 1.22285E-09     3.000  0
 11   30.000  180.000  230.618 9.84034E+00 5.33681E-06 8.02952E-10     3.000  0
 12   33.000  180.000  237.986 6.37697E+00 5.58153E-06 5.26885E-10     3.000  0
 13   36.000  180.000  245.863 4.19085E+00 5.77699E-06 3.46717E-10     3.000  0
 14   39.000  180.000  254.045 2.79317E+00 5.92083E-06 2.28798E-10     3.000  0
 15   42.000  180.000  261.192 1.71199E+00 6.04446E-06 2.26794E-10     5.000  0
 16   47.000  180.000  262.647 9.02470E-01 6.16620E-06 1.21182E-10     5.000  0
 17   52.000  180.000  252.087 4.22271E-01 6.00630E-06 8.60519E-11     8.000  0
 18   60.000  180.000  233.915 1.42768E-01 5.24701E-06 2.64888E-11     8.000  0
 19   68.000  180.000  218.931 4.46109E-02 4.11873E-06 6.66051E-12     8.000  0
 20   76.000  180.000  206.682 1.12244E-02 2.88473E-06 1.71313E-12    24.000  0
 21  100.000  180.000  226.916 1.78299E-04 1.05076E-07 8.56164E-16    20.000  0
                                                Total: 1.15556E-04   120.000
[eof]

Limb viewing, co2 only, with GRA Flag enabled (horizontal gradient mode, although no gradient applied hence down and up paths identical apart from Psi angle).
! Path diagnostics calculated for Tan Hgt=   5.000 [km] by RFM v.4.09
!27-APR-00
!  Rfr.Tan   Geo.Tan   Tan.Zen   Tan.Psi   Rad.Crv   Obs.Ele   Obs.Alt   Obs.Psi
!    5.000     6.044    90.000     0.000  6367.421
           1          44          44 = NGas, NSeg1, NSeg2
co2
Lev  Zlow[km]  Psi[dg] Temp[K]  Press[mb]  VMR[ppv]   Amt[kmol/cm2] Len.[km] Clc
 49  115.000   11.091  326.069 3.31580E-05 3.79538E-05 1.21510E-13    27.087  1
 48  110.000   10.856  264.033 5.71787E-05 5.21933E-05 3.45146E-13    27.700  1
 47  105.000   10.615  220.677 1.12542E-04 9.11164E-05 1.37425E-12    28.358  1
...etc
  8    7.000    1.862  239.623 3.84607E+02 3.30000E-04 2.40952E-05    37.873  1
  7    6.000    1.522  246.198 4.43280E+02 3.30000E-04 3.53127E-05    49.476  1
  6    5.000    1.077  253.597 5.17796E+02 3.30000E-04 9.69509E-05   119.784  1
                                                Total: 2.47231E-04  1247.991
  6    5.000    0.000  253.597 5.17796E+02 3.30000E-04 9.69509E-05   119.784  1
  7    6.000   -1.077  246.198 4.43280E+02 3.30000E-04 3.53127E-05    49.476  1
  8    7.000   -1.522  239.623 3.84607E+02 3.30000E-04 2.40952E-05    37.873  0
...etc
 47  105.000  -10.368  220.677 1.12542E-04 9.11164E-05 1.37425E-12    28.358  0
 48  110.000  -10.615  264.033 5.71787E-05 5.21933E-05 3.45146E-13    27.700  0
 49  115.000  -10.856  326.069 3.31580E-05 3.79538E-05 1.21510E-13    27.087  0
                                                Total: 2.47231E-04  1247.991
[eof]

Zenith viewing, co2 only
! Path diagnostics calculated for AirMass=   1.000      by RFM v.4.09
! 27-APR-00 demo
           1          49           0 = NGas, NSeg1, NSeg2
co2
Lev  Zlow[km]  Zen[dg] Temp[K]  Press[mb]  VMR[ppv]   Amt[kmol/cm2] Len.[km] Clc
  1    0.000  180.000  285.015 9.55900E+02 3.30000E-04 1.32985E-06     1.000  1
  2    1.000  180.000  278.516 8.46900E+02 3.30000E-04 1.20564E-06     1.000  1
  3    2.000  180.000  272.018 7.48100E+02 3.30000E-04 1.09038E-06     1.000  1
...etc
 47  105.000  180.000  221.063 1.11603E-04 9.05438E-05 2.37295E-13     5.000  1
 48  110.000  180.000  265.192 5.65723E-05 5.18274E-05 6.05628E-14     5.000  1
 49  115.000  180.000  327.066 3.29121E-05 3.78736E-05 2.20778E-14     5.000  1
                                                Total: 1.17960E-05   120.000
[eof]