MORSE .cov File

Type

Output

Filename

Specified by COVFIL parameter in *OUT section of the driver table.

Description

Retrieval Covariance Matrix for each retrieval.

This is a square matrix of dimensions the same as the retrieval state vector.

Structure

The .cov file follows the Common File Format except that the Common_Pixel_Data section is replaced by a Matrix Data section containing just the retrieval covariance matrix.

The size of the matrix, NX × NX is computed from

NX = ∑_i NLVPRF(i)

where NLVPRF(i), listed in the File Header section, are the sizes of the state vector component profiles for each retrieved species i.

The covariance matrix is symmetric, so can be read either as row index increasing first or column index increasing first.

For 'linear' retrieved quantities (temperatures mostly) the units of the covariance are the same as the state vector (eg K² along diagonal), and the diagonals should match the squares of the corresponding rtv_SD quantities in the .rtv file.
For 'logarithmically' retrieved quantities (VMRs, pressure) the units are ln(x). So, for example, a diagonal value of 10^-4 corresponds to a 1% uncertainty in the retrieval. Unless small, this will only approximately match the corresponding ratio (rtv_SD/rtv)² in the .rtv file. The rtv_SD value is calculated as
rtv_SD = rtv × ( exp ( s ) - 1 ) ≈ rtv × s for small s
where s is the square root of the diagonal element of SX.

Matrix Data
SX(1,1) SX(2,1) ...	Retrieval Covariance Matrix elements
... SX(NX,1) SX(1,2) ...
... SX(NX,NX)

Field	Type	Definition	Range
SX(NX,NX)	R	Retrieval covariance matrix	>0 along diagonal