.pth File

RFM File Formats: Ray Path Diagnostics

21SEP24
Type
Output(s), with PTH Flag.

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 (i.e., not HOM, NAD or ZEN flags) and Limb-viewing with a 2D atmosphere (GRA flag)
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
! Lev Zlow[km] Zen[dg] Temp[K] Press[hPa] VMR[ppv] Amt[kmol/cm2] Len.[km] Clc Header Record
  For i = 1, NSeg1:
    LEV(i) ALT(i) ANG(i) TEM(i) PRE(i) VMR(i) AMT(i) LEN(i) Path segment data
Total: TOTAMT TOTLEN            Totals
  For i = 1, NSeg2:
    LEV(i) ALT(i) ANG(i) TEM(i) PRE(i) VMR(i) AMT(i) LEN(i) Path segment data
Total: TOTAMT TOTLEN            Totals
[eof]

Fields
FieldFormatDescription 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[1] deg 0 – 90
PSITAN F10.3 (if GRA flag) Line-of-Sight Angle[2] at Tangent Pt deg ±180, else -999
RADCRV F10.3 Radius of Curvature [Definition] km
ELEOBS F10.3 (if *ELE section) Observer Elevation Angle deg ±90, else -999
ALTOBS F10.3 Observer Altitude km
PSIOBS F10.3 Observer LOS Angle deg
NGAS I10 No.of different molecules
NSEG1 I10 No.of path segments for ray on downward path[3]
NSEG2 I10 No.of path segments for ray on upward path[3]
GAS C7 Name of molecule, eg h2o
LEV(:) I3 (NSEGn) Atmospheric Profile Layer# 1 : NATM
ALT(:) F9.3 (NSEGn) Altitude of segment lower boundary[4] km BOA < : < TOA
ANG(:) F9.3 (NSEGn) Zenith or (GRA Flag) LOS angle at edge of seg nearest obs.[4] deg
TEM(:) F9.3 (NSEGn) Curtis-Godson Temperature K > 0
PRE(:) E12.5 (NSEGn) Curtis-Godson Pressure hPa BOA < : < TOA
VMR(:) E12.5 (NSEGn) Volume Mixing Ratio ppv 0 – 1
AMT(:) E12.5 (NSEGn) Absorber Amount kmol/cm2 > 0
LEN(:) F10.3 (NSEGn) Path Length km same for all molecules
TOTAMT E12.5 Total Amount in path kmol/cm2 > 0
TOTLEN F10.3 Total Length of path km same for all molecules

Notes
  1. ZENTAN is 90 for a 'true' tangent point, but if the ray intersects the surface or for an upward-viewing observation then this value is the angle between the ray and the local vertical (<90) instead.

  2. PSITAN is the angle subtended at the earth centre in the vertical plane including the observer and tangent point (see Definition).

  3. 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).

  4. 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.

  5. TOTAMT and TOTLEN refer only to the part of the path listed above, ie represent an addition of all the column entries.

Example
pth.asc_lin