*FLG Section

27MAR25

Type

Mandatory Section#2

Description

A series of 3-letter codes indicating various MORSE options to be 'switched on' (all switched off by default)

Format

Multiple 3-character fields of single type, any order, limited set of values.

Field	Type	Value	Description
FLG	C3	ACC	More stringent default accuracy/convergence criteria[1]
		AHY	Suppress hydrostatic equilibrium
		APR	Include A Priori profiles (as an extra SET) in .rtv files
		CLD	Use cloud detection
		COL	Add integrated column amounts to retrievals
		CTM	Use molecular (eg H2O) continuum data
		FGD	Use full, as opposed to irregular, grid
		FIX	Assume fixed relative altitudes (eg detector array)
		FMW	Use full microwindow (ie set all masks = TRUE)
		FVZ	Suppress FOV distortion due to refraction
		GEO	Use geometric (ie non-refractive) ray paths
		INF	Include information diagnostics in in .rtv
		LIN	Assume VMR varies linearly with altitude rather than logarithmically
		MIX	Use CO2 line mixing
		MWO	Write outputs after each microwindow in .rtv files
		QAD	Use simple quadratic fit to line wings rather than inverse quadratic (same as RFM)
		RES	Include vertical resolution factor in .rtv files
		RSM	Allow run to resume from last pixel

Details

ACC

Specifically scales the following default settings

Parameter	Default	ACC flag
Convergence Criteria (see *CNV)
MAXITR	10	×10
CHILIM	1.0	×0.1
DELCHI	0.1	×0.1

AHY

This decouples the pressure and temperature profiles so that these are treated as independent.

• Limb-sounding: retrieved independently without any consideration of altitude spacing
• Nadir-sounding: use explicit altitude grid for vertical path integrations

APR

This add a priori profiles as a separate SET in the output .rtv files.

CLD

Limb-viewing: Use CLDIDX, CLDRAD threshold values to remove cloud-contaminated spectra

Nadir-viewing: Use L1C or external cloud data to attempt to model cloud contribution

COL

For retrieved VMR profiles the .rtv file also includes partial column amounts, in mole/m², from each profile level to the top of the atmosphere, along with the SD of these amounts.

CLD

If listed as absorbing gases, this includes the continua associated with H2O, CO2, O2 and N2 (same as with the RFM CTM Flag).

FGD

If using an irregular spectral grid, either via the *GRD section or using a MIPAS Microwindow Database File (MDBFIL), this switches it off and uses a full, regular grid instead.

FIX

The default is to assume that the individual measurements contributing to a limb scan have some relative pointing uncertainty, so that the height/pressure at each tangent point is an independent unknown. With this flag, it is assumed that the relative heights are fixed, and so the hydrostatic equation can be used to reduce the problem to the tangent height/pressure at a single reference level.

FMW

For use with (MIPAS) microwindow database files (.mdb files). The database file contains the set of spectral masks which are applied by default. The effect of this flag is to remove these masks and use every point within the microwindow to construct the measurement vector.

FVZ

Same as RFM FVZ Flag. However, since MORSE only processes one limb-viewing direction at a time there is no efficiency benefit in using this flag.

GEO

Same as RFM GEO Flag. Sets refractive index to 1.

INF

Add 3 (scalar) diagnostics for each retrieved species to .rtv files

CSQ

Average χ² of deviation of retrieval from A Priori

DFS

Degrees of Freedom for Signal

INF

Information content

LIN

Same as RFM LIN Flag.

MIX

Same as RFM MIX Flag.

Example

*FLG CLD APR ! Use cloud-detection, include A Priori in .rtv files

• MORSE Index