RFM File Formats

.grd File: Irregular Grid

30DEC20

Type

Input(s), mandatory if GRD Flag enabled without LUT Flag.

Description

Irregular grid for spectral calculations (MIPAS-specific format - the irregular spectral file is probably more convenient for other uses)

Filename

Specified in *GRD section of Driver Table

Structure

This file format is formally described in ESA document PO-TN-OXF-GS-0010.

The following is the relevant structure for use in the RFM

CONFIG

ILSHDR

INTFNC

NPTS NUSE WNO1 WNOD

ALTMIN ALTMAX

HEXGRD(1:50)

HEXGRD(51:100)

...

HEXGRD(*:NPTS)

[eof]

Fields

Field	Type	Description	Range
`CONFIG`	C40	Configuration Info	Passed directly to `rfm.log`
`ILSHDR`	C80	Header record from assumed AILS file
`INTFNC`	C3	Interpolation Function	See table below
`NPTS`	I	Number of points in full grid	See Note 5
`NUSE`	I	Number of points in irregular grid	≥1
`WNO1`	D	Wavenumber [cm^-1] of 1st point

`WNOD`	D	Wavenumber spacing [cm^-1]

`ALTMIN`	R	Lower tangent altitude [km]

`ALTMAX`	R	Upper tangent altitude [km]

`HEXGRD`	Z	1 hex character=4 grid points

Type: I=Integer; Z=Hexadecimal; R=Real; D=Double Precision; Cn=character string, length n.

The INTFNC field (always lower case) may indicate any of the following interpolation methods :

INTFNC	Interpolation Function
`lin`	y = ax + b
`qad`	y = ax² + b + c
`cub`	y = ax³ + bx² +cx + d
`1li`	y = 1 / ( ax + b )
`1qa`	y = 1 / ( ax² + b + c )
`1cu`	y = 1 / ( ax³ + bx² +cx + d )
`1sq`	y = 1 / ( ax + b )²
`lor`	y = 1 / ( ax² + b )
`lnl`	y = exp ( ax + b )
`lnc`	y = exp ( ax³ + bx² +cx + d )

Notes

INTFNC: All MIPAS irregular grids use the lin function - simple linear interpolation.
NPTS refers to the number of points in the reconstructed regular grid, NUSE is the number which are calculated in the irregular grid.
HEXGRD is an array of hexadecimal characters, up to 50 per record, with the bit pattern of one character representing four grid points with the lowest wavenumber grid point corresponding to the most significant bit. Eg '8' means that only the lowest wavenumber in a group of 4 points is used for the irregular grid, '1' means that only the highest wavenumber is used, 'F' means that all 4 are used.
If NPTS is not a multiple of 4, the last HEXGRD character represents the extra 1,2 or 3 'grid points' as set to 0.
A negative value of NPTS is interpreted as defining spectral ranges in GHz rather than cm^-1

Example

PT__0039_lin_m_lut                                          
! MIPAS A-band nominal AILS supplied by H.Nett 22-DEC-00                        
lin   m   A    6.975   5.742                       ! Intpln. methd, band, tols  
   951   153    685.5250      0.0005               ! npts, nused, wn0, delta
  33  45                                           ! Altitude limits (km)
80000000000000000800000000000000000000000000000000
00000022000000000002000008429FF8AD4A56ED2822242204
404042FFEC892FFEBFFFBD5420008000008000012A44228FFF
FA92FFE4100400000004000000000000000020000000000000
00000000000000000000040000000000000002
[eof]

Bugs

[none recent]