## .svd File: Look Up Tables |

**Type**- Input(s), optional if
`SVD`enabled. **Description**- SVD (Singular Vector Decomposition)-compressed Look Up Tables of
absorption coefficient [m
^{2}/mole] for particular spectral range and absorber, generated for the MIPAS/Envisat instrument. **Filename(s)**- Specified in
`*SVD`section of Driver Table **Structure**- (also described in
ESA document PO-TN-OXF-GS-0011.txt)
`DATE TIME``#CMNT``MWCODE ID`[`.ISO`]`TAB``NL NV V1 DV NP P1 DP NT T1 DT``U`(IV,1)`U`(IV,2) ...... `U`(IV,NL)Repeat for IV=1,NV `K`(1,IX)`K`(2,IX) ...... `K`(NL,IX)Repeat for IX=1,NX [eof] **Fields**-
Field Type Description Range `DATE`C*11 File creation Date, as dd-mmm-yyyy (ignored) `TIME`C*15 File creation Time, as hh:mm:ss.mmmmmm (ignored) `#CMNT`C*80 At least one comment record Records start with '#' `MWCODE`C*8 Microwindow Label Matches `LABSPC``IDX`I HITRAN Index of absorber See List of Absorbers `.ISO`I (optional) ' `.`' then HITRAN Isotope#See List of Isotopes `TAB`C*3 Tabulation Function ' `LIN`', '`4RT`' or '`LOG`'`NL`I No. of Singular Values >0 `NV`I No. of Wavenumber Points >0 `V1`R*8 Lowest Wavenumber [cm ^{-1}]`DV`R*8 Wavenumber Increment [cm ^{-1}]`NP`I No. of -ln(p) Points >0 `P1`R*4 Lowest -ln(p) (p in [mb]) `DP`R*4 -ln(p) increment `NT`I No. of Temperature Points >0 `T1`R*4 Lowest Temperature [K] `DT`R*4 Temperature increment [K] `U`R*4 U(NV,NL) Matrix `K`R*4 K(NL,NX) Matrix, NX=NP*NT **Notes**- These files are generated for MIPAS -
for other purposes, the
`.tab`format look-up tables are recommended instead. - The File Header (ESA rather than RFM format) consists of 2 records,
the first of which is the 'time stamp' and the second is equivalent to an
RFM comment record. For this reason, the first two records of any
`.lut`files are written to the`rfm.runlog`file rather than just the usual first (comment) record. - The
`MWCODE ...`record is read with specific formats:-
`(A8,X,I2,X,A3)`(not isotopic) -
`(A8,X,I2,X,I1,X,A3)`(isotopic)

`.`' character in position 12 -
- The value
`NL`> 0 is actually what is used to determine that this is a SVD-compressed LUT, a value 0 would indicate a`.tab`file. - The absorption coefficient is intrinsically a 3 dimensional table with wavenumber, pressure and temperature axes. However for the purposes of Singular Value Decomposition the p,T indices are combined into a single X index: (P1,T1), (P1+DP,T1), ... (P1+(NP-1)*DP,T1+(NT-1)*DT)
- To reconstruct the absorption coefficient first the
matrix is reconstructed as
F(IV,IX) = SUM (

The relationship between F and the absorption coefficient is determined by`U`(IV,IL) *`K`(IL,IX) )`TAB`(for MIPAS, TAB is usually`LOG`so Abs.Coeff = exp(F)) - The
`K`Matrix is actually written in the file in the natural form for the transpose of`K`- this has the minor advantage of maintaining a constant length (`NL`) for each 'row' of both the`U`and`K`matrices.

- These files are generated for MIPAS -
for other purposes, the
**Example**01-NOV-2002 12:00:00.000000 # MIPAS SVD-compressed LUT created by LUTINI v.16MAR02 PT__0001 1 LOG 7 6701 686.225 0.0005 9 -3.40120 1.00080 9 180.000 16.000 -1.4469028E-02 1.5561746E-02 -1.6158378E-03 -7.6377830E-05 6.6569343E-04 -1.3192989E-03 -2.3304068E-03 -1.4468588E-02 1.5558815E-02 -1.6167151E-03 -7.6754986E-05 6.6715060E-04 -1.3191579E-03 -2.3323591E-03 .... [eof]