MIPAS L2 Error Analyses

Last Updated: 07MAR17 - add MA mode errors


The following table shows the linear error analyses for MIPAS L2 products. These errors have been evaluated for 5 different atmospheric conditions.
DAY
Mid-Latitude day-time (similar to US Standard Atmosphere)
NGT
Mid-Latitude night-time
SUM
Polar Summer day-time
WIN
Polar Winter night-time
EQU
Equatorial day-time

Click on 'Data' for the numerical data that has been plotted. In the plots, the same symbols are used for each error source (explained below) throughout, and listed in the key in the approximate order of significance for that plot. Only the most significant errors are plotted. Click on the atmosphere or species for plots of the atmospheric profiles assumed.

MODE: FR17 (2002-2004, 17 sweeps @ 0.025 cm-1 sampling)
Species DAY NGT WIN SUM EQU

TEM [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
PRE [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
H2O [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
O3 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
HNO3 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
CH4 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
N2O [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
NO2 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]

CLONO2 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
F11 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
F12 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
N2O5 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]

CCL4 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
COF2 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
F14 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
F22 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
HCN [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]

C2H2 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
C2H6 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
CH3CL [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
CLO [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
COCL2 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
F113 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
F114 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
H2O2 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
HOCL [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
OCS [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
SF6 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]

MODE: OR27 (2005-2012, 27 sweeps @ 0.0625 cm-1 sampling)
Species DAY NGT WIN SUM EQU

TEM [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
PRE [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
H2O [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
O3 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
HNO3 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
CH4 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
N2O [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
NO2 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]

CLONO2 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
F11 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
F12 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
N2O5 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
C2H6 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]

CCL4 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
COF2 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
F14 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
F22 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
HCN [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]

C2H2 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
C2H6 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
CH3CL [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
CLO [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
COCL2 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
H2O2 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
F113 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
F114 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
HOCL [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
OCS [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
SF6 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]

MODE: MA (2005-2012, 29 sweeps @ 0.0625 cm-1 sampling)
Species DAY NGT WIN SUM EQU

TEM [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
PRE [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
H2O [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
O3 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
HNO3 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
CH4 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
N2O [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
NO2 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]

CLONO2 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
F11 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
F12 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]
N2O5 [Prof] [MW] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data] [Plot] [Data]

List of errors considered

TOT
Total Error. Root sum square of all SYS and RND components
RND
Random Error. Due to the propagation of instrument noise through the retrieval.
NB: A more accurate assessment of this component is included in the L2 product
NONLTE
Non-LTE error. Due to assumption of local thermodynamic equilibrium when modelling emission in the MIPAS forward model. Based on calculations using vibrational temperatures supplied by M.Lopez-Puertas, IAA, Granada.
SPECDB
Spectroscopic database errors. Due to uncertainties in the strength, position and width of infrared emission lines. Based on estimates supplied for each molecule/band by J.M.Flaud, LPM, Paris.
GAIN
Radiometric Gain Uncertainty (spectrally correlated), assumed to be 1%.
GAIN_SU
Radiometric Gain Uncertainty (spectrally uncorrelated between microwindows). Due mostly to non-linearity correction in bands A, AB and B. A value of ±2% has been assumed for bands A, AB and B, and ±1% for bands C and D
SPREAD
Uncertainty in width of apodised instrument line shape (AILS). A value of 0.2% has been assumed based on likely variations in apodised instrument line shape from modelled.
SHIFT
Uncertainty in the spectral calibration. The design specification of ±0.001cm-1 has been used, and is consistent with the 1st derivatives signatures in the residual spectra.
CO2MIX
CO2 line-mixing. Due to neglecting line-mixing effects in the retrieval forward model (only affects strong CO2 Q branches in the MIPAS A and D bands)
CTMERR
Uncertainty in gaseous continua. Assumes an uncertainty of ±25% in the modelling of continuum features of H2O (mostly), CO2, O2 and N2.
GRA
Horizontal gradient effects. Due to retrieval assuming a horizontally homogeneous atmosphere for each profile. Error is calculated assuming a ± 1K/100km horizontal temperature gradient.
HIALT
Uncertainty in high-altitude column. Retrieval assumes a fixed-shape of atmospheric profile above the top retrieval level. Effect is calculated assuming `true' profile can deviate by climatological variability.
PT
Propagation of pT random covariance into VMR retrieval
[species]
Uncertainties in assumed profiles of contaminant species. For most species this is the climatological 1-sigma variability (profiles supplied by J.Remedios, U.Leicester). However, for contaminant species which are also retrieved by MIPAS (ie CH4,H2O,HNO3,N2O,NO2,O3) the retrieval total error is assumed where this is smaller than the climatological variability.

Use of Systematic Errors

The definition of 'systematic error' here includes everything which is not propagation of the random instrument noise through the retrieval. However, to use these errors in a statistically correct manner for comparisons with other measurements is not straightforward. Each systematic error has its own length/time scale: on shorter scales it contributes to the Bias and on longer scales contributes to the SD of the comparison.

Fortunately, two of the larger systematic errors (PT and SPECDB) can be treated properly:

The pT propagation error (PT) is uncorrelated between any two MIPAS profiles (since it is just the propagation of the random component of the pT retrieval error through the VMR retrieval) so contributes to the SD of any profile comparison

Spectroscopic database errors (SPECDB) are constant but of unknown sign, so will always contribute to the Bias of any comparison, but note that the magnitude of these errors is very uncertain.

Of the other significant errors, the calibration-related errors (GAIN, SHIFT, SPREAD) should, in principle, be uncorrelated between calibration cycles however analysis of the residuals suggests that these errors are almost constant so could be included in the Bias.

The horizontal gradient (GRA), high altitude column (HIALT) and contaminant gas errors ([species]) are likely to be correlated over small areas (1000km) or times (weeks), hence contribute to the Bias for localised comparisons, but as the comparison datasets are extended these errors will contribute more to the SD.

Line mixing errors (CO2MIX) are also contribute towards the Bias but in principle the sign of these errors is known (unlike spectroscopic errors) so this bias could be removed. Non-LTE errors (NONLTE) should also, in principle, contribute a known Bias but these are highly variable (especially diurnally) so care has to be taken to make sure that representative conditions for the comparison are used.

Reference

Microwindow Selection for High-Spectral-Resolution Sounders
App. Optics, 41, 3665, 2002
Dudhia, A., V. L. Jay and C. D. Rodgers.