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MIPAS Data Formats Products
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2 MDSR per MDS 1 forward sweep 1 reverse sweep
2 MDSRs per MDS 1 forward sweep 1 reverse sweep
LOS calibration GADS
Spectral Lines MDS
P T Retrieval MW ADS
VMR Retrieval Parameters GADS
P t Retrieval GADS
Framework Parameters GADS
Processing Parameters GADS
Inverse LOS VCM matrices MDS
General GADS
Occupation matrices for vmr#1 retrieval MDS
MDS2 -- 1 mdsr forward sweep 1 mdsr reverse
Occupation matrices for p T retrieval MDS
General GADS
Priority of p T retrieval occupation matices
P T occupation matrices ADS
MIP_NLE_2P SPH
Summary Quality ADS
Instrument and Processing Parameters ADS
Microwindows occupation matrices for p T and trace gas retrievals
Scan information MDS
Level 2 product SPH
MDS1 -- 1 mdsr forward sweep 1 mdsr reverse sweep
H2O Target Species MDS
P T and Height Correction Profiles MDS
Continuum Contribution and Radiance Offset MDS
Structure ADS
Summary Quality ADS
Residual Spectra mean values and standard deviation data ADS
PCD Information of Individual Scans ADS
Instrument and Processing Parameters ADS
Microwindows Occupation Matrices ADS
Scan Information MDS
1 MDSR per MDS
Scan Geolocation ADS
Mipas Level 1B SPH
Calibrated Spectra MDS
Structure ADS
Summary Quality ADS
Offset Calibration ADS
Scan Information ADS
Geolocation ADS (LADS)
Gain Calibration ADS #2
Gain Calibration ADS #1
Level 0 SPH
DSD#1 for MDS containing VMR retrieval microwindows data
DSD for MDS containing p T retrieval microwindows data
VMR #1 retrieval microwindows ADS
P T retrieval microwindows ADS
1 MDSR per MDS
VMR profiles MDS (same format as for MIP_IG2_AX)
Temperature profiles MDS (same format as for MIP_IG2_AX)
Pressure profile MDS (same format as for MIP_IG2_AX)
P T continuum profiles MDS (same format as for MIP_IG2_AX)
GADS General (same format as for MIP_IG2_AX)
Level 0 MDSR
Values of unknown parameters MDS
Computed spectra MDS
Jacobian matrices MDS
General data
Data depending on occupation matrix location ADS
Microwindow grouping data ADS
LUTs for p T retrieval microwindows MDS
GADS General
P T retrieval microwindows ADS
ILS Calibration GADS
Auxilliary Products
MIP_MW1_AX: Level 1B Microwindow dictionary
MIP_IG2_AX: Initial Guess Profile data
MIP_FM2_AX: Forward Calculation Results
MIP_CS2_AX: Cross Sections Lookup Table
MIP_CS1_AX: MIPAS ILS and Spectral calibration
MIP_CO1_AX: MIPAS offset validation
MIP_CL1_AX: Line of sight calibration
MIP_CG1_AX: MIPAS Gain calibration
MIP_SP2_AX: Spectroscopic data
MIP_PS2_AX: Level 2 Processing Parameters
MIP_PS1_AX: Level 1B Processing Parameters
MIP_PI2_AX: A Priori Pointing Information
MIP_OM2_AX: Microwindow Occupation Matrix
MIP_MW2_AX: Level 2 Microwindows data
MIP_CA1_AX: Instrument characterization data
Level 0 Products
MIP_RW__0P: MIPAS Raw Data and SPE Self Test Mode
MIP_NL__0P: MIPAS Nominal Level 0
MIP_LS__0P: MIPAS Line of Sight (LOS) Level 0
Level 1 Products
MIP_NL__1P: MIPAS Geolocated and Calibrated Spectra
Level 2 Products
MIP_NLE_2P: MIPAS Extracted Temperature , Pressure and Atmospheric Constituents Profiles
MIP_NL__2P: MIPAS Temperature , Pressure and Atmospheric Constituents Profiles
Glossary
References
Glossaries of technical terms
Level 2 processing
Pointing
Miscellaneous hardware and optical terms
Spectrometry and radiometry
Data Processing
Alphabetical index of technical terms
Frequently Asked Questions
The MIPAS Instrument
Inflight performance verification
Instrument characteristics and performances
Preflight characteristics and expected performances
Subsystem description
Payload description and position on the platform
MIPAS Products and Algorithms
Data handling cookbook
Characterisation and calibration
Calibration
Latency, throughput and data volume
Auxiliary products
Level 2
Instrument specific topics
Algorithms and products
Level 2 products and algorithms
Products
The retrieval modules
Computation of cross-sections
Level 1b products and algorithms
Products
Calculate ILS Retrieval function
Level 1a intermediary products and algorithms
Product evolution history
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MIPAS Products User Guide
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2.4.4.2 Products

2.4.4.2.1 Level 2 Products Description

There exists 2 forms of level 2 products. The level 2 product 2.4.4.2.1.1. itself and the level 2 NRT / meteo product 2.4.4.2.1.2. containing a subset of the data contained in the relating level 2 product.

2.4.4.2.1.1 Level 2 Product

Table 2.3
Product Header 2.4.4.2.1.3. Main Product Header 2.4.4.2.1.3.1.
Specific Product Header 2.4.4.2.1.3.2.
Data Set Descriptors 2.4.4.2.1.3.3.
Summary Quality ADS 2.4.4.2.1.4.
Scan Geolocation ADS 2.4.4.2.1.5.
Structure ADS 2.4.4.2.1.6.
Scan Information MDS 2.4.4.2.1.7.
p,T Retrieval MDS 2.4.4.2.1.8.
Species #1 VMR Retrieval MDS 2.4.4.2.1.9. a
Species #2 VMR Retrieval MDS 2.4.4.2.1.9. a
Species #3 VMR Retrieval MDS 2.4.4.2.1.9. a
Species #4 VMR Retrieval MDS 2.4.4.2.1.9. a
Species #5 VMR Retrieval MDS 2.4.4.2.1.9. a
Species #6 VMR Retrieval MDS 2.4.4.2.1.9. a
Continuum and Offset MDS 2.4.4.2.1.10.
PCD Information ADS 2.4.4.2.1.11.
MW Occupation Matrix ADS 2.4.4.2.1.12.
Residual Spectra ADS 2.4.4.2.1.13.
Parameters ADS 2.4.4.2.1.14.
a: Sequence of species is given in Specific Product Header

The level 2 product consists of following elements (see index)

The detailed structure of the level 2 product can be found here .

2.4.4.2.1.2 Level 2 NRT /Meteo Product

Table 2.4
Product Header 2.4.4.2.1.3. Main Product Header 2.4.4.2.1.3.1.
Specific Product Header 2.4.4.2.1.3.2.
Data Set Descriptors 2.4.4.2.1.3.3.
Summary Quality ADS 2.4.4.2.1.4.
Scan Geolocation ADS 2.4.4.2.1.5.
Structure ADS 2.4.4.2.1.6.
Scan Information MDS 2.4.4.2.1.7.
p,T Retrieval MDS 2.4.4.2.1.8.
O3 Retrieval MDS 2.4.4.2.1.9.
H2O Retrieval MDS
MW Occupation Matrix ADS 2.4.4.2.1.12.
Parameters ADS 2.4.4.2.1.14.

The level 2 NRT / Meteo product consists of following elements (see index)

The detailed structure of the level 2 NRT / Meteo product can be found here .

2.4.4.2.1.3 Product Header

The product header is divided into three parts:

2.4.4.2.1.3.1 Main Product Header

The main product header is the same for all ENVISAT products. It specifies basic product information such as origin of data, processing site, processing software version, UTC time of data sensing and processing, orbit and velocity parameters of ENVISAT, quality indicators for input data, etc.
The detailed structure of the MPH can be found here 6.5.1. .

2.4.4.2.1.3.2 Specific Product Header

The SPH is the same for both forms of level 2 products. It contains information applicable to the whole level 2 product file such: The detailed structure of the level 2 SPH can be found here 6.5.50. .

2.4.4.2.1.3.3 Data Set Descriptors

The DSD provide information on structure and size of included or referenced measurement and annotation data.

2.4.4.2.1.4 Summary Quality ADS

This ADS consists of 1 ADSR containing the numbers of p,T and VMR retrievals terminated unsuccessful because of
  • excess of allowed number of macro iterations
  • excess of allowed number of micro iterations
  • excess of allowed processing time
The detailed structure of this ADS is slightly different for the 2 forms of level 2 products. It can be found here 6.5.45. for the full level 2 product and here 6.5.54. for the NRT / meteo product.

2.4.4.2.1.5 Scan Geolocation ADS

This ADS contains 1 ADSR per scan providing geolocation information. It includes: The detailed structure of this ADS is the same for both forms of level 2 products. It can be found here 6.5.39. .

2.4.4.2.1.6 Structure ADS

This ADS provides the parameters which determine the size of the DSRs of the following MDSs and ADSs. A new ADSR is added every time one of these parameter change its value. Each ADSR contains:
  • The number of sweeps per scan.
  • The numbers of retrieved profile, continuum and offset values.
  • Indicators for existence of p,T error propagation data.
  • The numbers of microwindows.
  • The numbers of spectral grid points.
  • Offsets and size of first DSRs within the following MDSs and ADSs this ADSR refers to.
The detailed structure of this ADS can be found here 6.5.46. . It is the same for both forms of level 2 products, but within the NRT / meteo product several fields are not used.

2.4.4.2.1.7 Scan Information MDS

This MDS contains 1 MDSR per scan providing geolocation information of the individual sweeps and a subset of the relating retrieval results. It includes:
  • The ZPD time of each sweep of the scan.
  • The WGS84 latitude and longitude of the tangent points of each sweep of the scan.
  • The altitudes of the tangent points of each sweep of the scan.
  • Flags indicating success of p,T and VMR retrievals.
  • The logical retrieval vectors for p,T and VMR retrievals.
  • The corrected altitudes for each sweep.
  • Retrieved pressure, temperature and VMR profiles.
  • Concentration and vertical column density profiles.
  • Variance data for height correction, pressure, temperature, VMR , concentration and vertical column density.
The detailed structure of this MDS is slightly different for the 2 forms of level 2 products. It can be found here for the full level 2 product and here for the NRT / meteo product.

2.4.4.2.1.8 PT Retrieval MDS

This MDS contains 1 MDSR per scan providing the following results of the p,T retrieval:
  • The condition terminating the iterations.
  • The last value of chi2.
  • The source of used initial guess data.
  • Height correction and retrieved pressure and temperature profiles.
  • Variance/covariance matrices for pressure, temperature and height correction.
  • The pressure/temperature covariance data.
The detailed structure of this MDS is the same for both forms of level 2 products. It can be found here 6.5.48. .

2.4.4.2.1.9 VMR Retrieval MDSs

For each of the target species H2O, N2O, HNO3, CH4, O3 and NO2 1 VMR retrieval MDS is contained in the full level 2 product. The sequence of the species is given in the specific product header. The NRT / meteo product contains 2 of these MDSs covering O3 and H2O. Each of these MDSs contains 1 MDSR per scan providing the following results of the VMR retrieval:
  • The condition terminating the iterations.
  • The last value of chi2.
  • The source of used initial guess data.
  • VMR, concentration and vertical column density profiles together with the relating variance/covariance matrices.
  • The p,T error propagation variance/covariance matrix, if available.
The detailed structure of this MDS is the same for both forms of level 2 products. It can be found here 6.5.49. .

2.4.4.2.1.10 Continuum and Offset MDS

This MDS contains 1 MDSR per scan providing for p,T and VMR retrievals the results concerning continuum and offset fit. It includes:
  • For each microwindow the fitted instrument offset and relating variance data.
  • For all altitudes used for continuum fit the fitted or interpolated continuums together with the relating microwindows, grouping types and the covariance with fitted VMR, resp. fitted pressure and temperature.
This MDS is not contained in the NRT / meteo product. The detailed structure can be found here 6.5.47. .

2.4.4.2.1.11 PCD Information ADS

This ADS contains 1 ADSR per scan providing information on retrieval quality for p,T and VMR retrievals. It includes:
  • The numbers of iterations performed.
  • The partial chi2 depending on sweep and microwindow.
  • The evolution of chi2, lambda and retrieved parameters during macro iterations.
  • Additional information produced by the processor in textual form.
This ADS is not contained in the NRT / meteo product. The detailed structure can be found here 6.5.43. .

2.4.4.2.1.12 MW Occupation Matrix ADS

This ADS provides information on the microwindows selected for p,T and VMR retrievals. A new ADSR is added every time the selection changes. It includes:
  • For each sweep the labels of the selected microwindows (all retrievals).
  • For each retrieval the logical retrieval vector.
The detailed structure of this ADS is the same for both forms of level 2 products. It can be found here 6.5.41. .

2.4.4.2.1.13 Residual Spectra ADS

This ADS provides information on the residual spectra. A new ADSR is added every time the microwindow selection changes. It includes for each retrieval:
  • The mean values and standard deviations of residual spectra computed from all scans covered by current ADSR .
  • The number of retrievals contributing to the current ADSR .
  • The spectral mask relating to the current data.
This ADS is not contained in the NRT / meteo product. The detailed structure can be found here 6.5.44. .

2.4.4.2.1.14 Parameters ADS

This ADS provides information on instrument and processing parameters. It contains:
  • The actual elevation angles for current scan.
  • The pressure levels relating to the retrieved profiles.
  • The allowed number of macro and micro iterations.
The detailed structure of this ADS is slightly different for the 2 forms of level 2 products. It can be found here 6.5.42. for the full level 2 product and here 6.5.53. for the NRT / meteo product.

2.4.4.2.2 Extraction of Profile Data from Level 2 Products

There are 2 ways to extract profile data from level 2 products. If neither covariance data nor continuum and offset data is requested, the data can be extracted from the Scan Information MDS. Variance/covariance data for retrieved pressure, temperature and height correction can be extracted from the p,T retrieval MDS. Variance/covariance data for retrieved VMR, concentration and vertical column density can be extracted from the VMR retrieval MDSs. Continuum and offset data has to be extracted from the Continuum and Offset MDS.
Extraction of Profile Data from Scan Information MDS
The Scan Information MDS contains a subset of the p,T and VMR retrieval results. Within this MDS all fields containing profile information are of size Nsw 6.5.46. . For sweeps not used for fit the logical retrieval vectors (lfit) contain 0 and the relating profile entries are set to NaN. Extraction of p,T Retrieval Data For the extraction of the p,T retrieval data for the ith sweep, the ith entry of the logical retrieval vector for p,T retrieval (lfit) has to be checked. If it is 0, the ith sweep has been not been used for p,T retrieval and therefore the ith entries of the profiles of pressure, variance of pressure, corrected altitudes, variance of height correction, temperature and variance of temperature are set to NaN. Otherwise these entries contain the profile data related to the ith sweep as shown in table below.
 
Table 2.5
sweep index tangent height, geolocation, time lfit pressure, temperature, corrected height
variance of pressure, temperature and height correction
0 valid value 1 valid value
1 valid value 1 valid value
2 valid value 1 valid value
3 valid value 0 NaN
4 valid value 1 valid value
5 valid value 1 valid value
6 valid value 1 valid value
7 valid value 1 valid value
8 valid value 1 valid value
9 valid value 1 valid value
10 valid value 1 valid value
11 valid value 1 valid value
12 valid value 0 NaN
13 valid value 1 valid value
14 valid value 1 valid value
15 valid value 0 NaN
Extraction of VMR Retrieval Data For the extraction of the VMR retrieval data of the ith sweep, the ith entry of the relating logical retrieval vector (lfit) has to be checked. If it is 0, the ith sweep has been not been used for fit in species #1 VMR retrieval and therefore the ith entries of the profiles of VMR, variance of VMR, concentration, variance of concentration, vertical column density and variance of vertical column density are set to NaN. Otherwise these entries contain the profile data related to the ith sweep, as shown in the table below.
Relating altitude, pressure and temperature information can be extracted as described above.
 
Table 2.6
sweep index lfit p,T p,T retrieval profiles lfit VMR VMR, concentration, vertical column density
variance of VMR, concentration and vertical column density
0 1 valid value 0 NaN
1 1 valid value 1 valid value
2 1 valid value 1 valid value
3 0 NaN 0 NaN
4 1 valid value 1 valid value
5 1 valid value 1 valid value
6 1 valid value 1 valid value
7 1 valid value 1 valid value
8 1 valid value 1 valid value
9 1 valid value 1 valid value
10 1 valid value 0 NaN
11 1 valid value 0 NaN
12 0 NaN 0 NaN
13 1 valid value 0 NaN
14 1 valid value 0 NaN
15 0 NaN 0 NaN
Extraction of Profile and VCM Data from p,T Retrieval MDS
Within the p,T retrieval MDS 6.5.48. only the sweeps used for p,T retrieval are considered. Therefore the size of the fields containing profile information are of size NpT 6.5.46. . For height correction NpT-1 profile are used because no height correction is applied to lowest used sweep. Extraction of Profile Data For the extraction of pressure 6.5.48. , temperature 6.5.48. and height correction 6.5.48. profiles from the p,T retrieval MDS, the relating logical retrieval vector has to used to determine the profile indices relating to requested sweep indices, as shown in the example below.
 
Table 2.7
sweep index lfit p,T index on pressure and temperature profile index on height corrections
0 1 0 0
1 1 1 1
2 1 2 2
3 0 - -
4 1 3 3
5 1 4 4
6 1 5 5
7 1 6 6
8 1 7 7
9 1 8 8
10 1 9 9
11 1 10 10
12 0 - -
13 1 11 11
14 1 12 -
15 0 - -
Extraction of VCM Data The mapping between sweep indices and the indices on the variance/covariance matrices in the p,T retrieval MDS is the same as shown above.
For the symmetric variance covariance matrices for pressure 6.5.48. , temperature 6.5.48. and height correction 6.5.48. only the diagonal elements and the elements below are included in the MDS, as shown below.
Table 2.8
element[0,0]        
element[1,0] element[1,1]      
element[2,0] element[2,1] element[2,2]    
...     ...  
element[n,0] element[n,1] element[n,2] ... element[n,n]
Extraction of Profile and VCM Data from VMR Retrieval MDS
Within the VMR retrieval MDSs 6.5.49. only the sweeps used for relating VMR retrieval are considered. Therefore the size of the fields containing profile information are of size NV(i) 6.5.46. . Extraction of Profile Data For the extraction of VMR 6.5.49. , concentration 6.5.49. and vertical column density 6.5.49. profiles from the VMR retrieval MDSs, the relating logical retrieval vector has to used to determine the profile indices relating to requested sweep indices, as shown in the example below.
 
Table 2.9
sweep index lfit VMR index on VMR, concentration and vertical column density profile
0 0 -
1 1 0
2 1 1
3 0 -
4 1 2
5 1 3
6 1 4
7 1 5
8 1 6
9 1 7
10 0 -
11 0 -
12 0 -
13 0 -
14 0 -
15 0 -
Extraction of VCM Data The mapping between sweep indices and the indices on the variance/covariance matrices in the VMR retrieval MDSs is the same as shown above.
For the symmetric variance covariance matrices for VMR 6.5.48. , concentration 6.5.48. and vertical column density 6.5.48. only the diagonal elements and the elements below are included in the MDS, as shown above.
Extraction of Data from Continuum and Offset MDS
Within the Continuum and Offset MDS the fitted continuum and offsets of all retrievals are reported. Extraction of Offset Data For each retrieval  fields of size Noffset(pT) 6.5.46. , respectively Noffset(V(i)) 6.5.46. are contained in the Continuum and Offset MDS containing the offset values 6.5.47. itself, the relating variance data 6.5.47. and the labels of the relating microwindows 6.5.47. . Extraction of Continuum Data For the extraction of continuum the parameters number of altitudes used for continuum fit (Ncgid(pT) 6.5.46. , Ncgid(V(i)) 6.5.46. ) and max. number of microwindows per height (NMWPT 6.5.46. , NMWV(i) 6.5.46. ) are needed. For each retrieval the indices of sweeps 6.5.47. used for continuum fit is given in the MDS.
For each of these sweeps the labels of the used microwindows 6.5.47. , the grouping types 6.5.47. of these microwindows and the continuum 6.5.47. at these microwindows is given. For all microwindows with grouping types 1 .. 4 additionally the variance of the fitted continuum 6.5.47. and the covariance with the fitted profile (i.e. for p,T retrieval covariance of continuum and pressure 6.5.47. and covariance of continuum and temperature 6.5.47. , for VMR retrieval covariance of continuum and VMR 6.5.47. ) at this sweep is given. All of these fields are of size NMWPT 6.5.46. , respectively NMWV(i) 6.5.46. with unused fields set to default values. The following table shows an example.
 
Table 2.10
sweep index microwindow grouping type continuum variance, covariance
10 PT__0001 3 valid value valid values
PT__0002 5 valid value NaN b
PT__0010 1 valid value valid values
blank a -1 a NaN a NaN a
11 PT__0002 1 valid value valid values
PT__0010 2 valid value valid values
PT__0011 6 valid value NaN b
PT__0012 2 valid value valid values
13 PT__0002 1 valid value valid values
PT__0012 1 valid value valid values
PT__0020 1 valid value valid values
blank a -1 a NaN a NaN a
14 PT__0012 1 valid value valid values
PT__0020 1 valid value valid values
blank a -1 a NaN a NaN a
blank a -1 a NaN a NaN a
a unused field
b relating continuum value is not fitted, but interpolated (grouping type > 4)

 
 

2.4.4.3 Appendix A: Mapping of temperature error on to the retrieved VMR profiles

At a generic iteration, the VMR profile y is obtained applying to the profile y 0 of the previous iteration the correction:

image eq 2.43
where n is the residuals vector, image is the VCM of the observed spectra and K is the jacobian of the VMR retrieval.

An uncertainty image on the assumed tangent pressures and temperatures, translates into an error image on the simulated spectra and therefore into an error image on the retrieved profile equal to:

image eq 2.44
where C is the matrix accounting for p,T error propagation in the simulated spectra of VMR retrieval and contains the derivatives:
image eq 2.45
The index 'i' identifies the fitted spectral points (as a function of frequency for all the microwindows and all the tangent altitudes) and the index 'j' identifies the retrieved tangent altitudes. In equation (A2) D is assumed locally independent on p,T (always true for small errors image).
As the error on the retrieved p,T is described by a VCM image, the corresponding VCM image relating to y and due to p,T error is given by:
image eq 2.46
where we have defined E = DC. E is the matrix transforming p,T error into VMR error.

Matrix E depends on:

  • current atmospheric status (p,T and VMR)
  • observation geometry
  • set of adopted MWs in VMR retrieval (Occupation Matrix)
In MIPAS Level 2 processor each OM has a pT error propagation matrix E attached to it. Since OMs are tabulated for latitude bands, it is possible to use different E matrices for different latitude bands (of course this does not prevent from using the same OM throughout the whole orbit and different E matrices depending on latitude).

Matrix E and image are both outputs of MIPAS Level 2 processor. The users should use Equ. (A4) to derive the VMR error component due pT error propagation.

The dependencies of the pT error propagation on latitude, atmospheric model and acquisition scenario are analyzed, quantified and discussed in [39] Ref. [1.57 ] .
 

2.4.4.4 Appendix B: Algorithm for generation of the optimized microwindow databases


Microwindow selection is performed by an algorithm which simulates the propagation of random and systematic errors through a retrieval and attempts to maximise the information content Bennett, V. L., A. Dudhia and C. D. Rodgers Ref. [1.69 ] .  The information content of a microwindow increases as the log of the determinant of the total covariance decreases, total covariance being the sum of the random and various systematic error covariances.  Broadly speaking, 1 `bit' of information is equivalent to a factor 2 reduction in the uncertainty at one profile altitude.
Microwindows are created by first selecting a number of single measurements, identified by location in the spectral and tangent altitude grids, as starting points.  Adjacent measurements are added to each until the information content no longer improves or a maximum width of 3cm-1 is reached. The best of these trial microwindows is selected, the retrieval covariance modified, and the process repeated for a new set of measurements as starting points.  The procedure of growing microwindows also allows for measurements within microwindows to be `masked', i.e., excluded from the retrieval. This usually applies to measurements where the associated systematic errors such as the uncertainty in modelling a contaminant, outweigh any benefit in the reduction of the random error when considering the total covariance.
Initially, a set of typically 10 microwindows, or 10000 measurements (whichever occurs first) is selected based on the assumption that spectra for all MIPAS bands are available. Further microwindows are then selected to maximise information retrieved in situations where data
from different bnds may be unavailable. This set of 20-30 microwindows constitutes the database.
Occupation Matrices (OM) represent subsets of microwindows to be used under different retrieval circumstances, and these are constructed using the same approach: selecting the microwindows from the database (rather than growing new microwindows) in the sequence which maximises the retrieved information. A number of these OMs are precomputed, corresponding to different band-availabilities, and associated with each of these is a single figure-of-merit representing the information content.

References: see Bennett, V. L., A. Dudhia and C. D. Rodgers Ref. [1.69 ]

2.4.4.5 Appendix C: Handling of initial guess profiles

For the analysis of a given scan, the retrieval code needs the following atmospheric profiles as input:

  • Pressure and temperature profiles
  • Continuum profiles for microwindows used in p,T retrieval
  • H2O VMR profile
  • Continuum profiles for microwindows used in H2O retrieval
  • O3 VMR profile
  • Continuum profiles for microwindows used in O3 retrieval
  • HNO3 VMR profile
  • Continuum profiles for microwindows used in HNO3 retrieval
  • CH4 VMR profile
  • Continuum profiles for microwindows used in CH4 retrieval
  • N2O VMR profile
  • Continuum profiles for microwindows used in N2O retrieval
  • NO2 VMR profile
  • Continuum profiles for microwindows used in NO2 retrieval
  • VMR profiles for other contaminants.
These profiles are used in the different retrievals either as a first guess of the profiles that are going to be retrieved or as assumed profiles of the atmospheric model (profiles of interfering species and p,T profiles in the case of VMR retrievals).

For each of these profiles both an a-priori estimate and the result of the 'most recent measurement' (obtained either from the retrieval of the previous scans or from a previous retrieval of the same scan) are available. The a-priori estimate of a profile is obtained either from climatology or from the ECMWF.

On the light of the fact that in some cases the errors of the retrieved profiles may be very large (VMR retrieval at very low altitudes, continuum retrieval), using the 'most recently' retrieved profiles as initial guess for the retrieval may not be a good strategy. In MIPAS Level 2 processor, the initial guess / assumed profiles are obtained using the 'best estimate' of the profiles available at the time when the retrieval is started.

For pressure and temperature profiles the 'best estimate' coincides with the 'most recent measurement'. For continuum profiles the 'best estimate' coincides with their a-priori estimate. For all the other profiles, the 'best estimate' is obtained by calculating the optimal estimation (weighted average) between the most recently measured profiles and the a-priori ones.

The optimal estimation consists in weighting the retrieved profile, with its covariance matrix, with the a-priori profile, which is also characterized by a covariance matrix with eventually large diagonal values.

The optimal estimation of the profiles is determined not only at the beginning of each scan analysis, but also after each VMR retrieval, because the retrieved VMR profile is used as assumed profile in the subsequent retrievals (from the same scan).
 


Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry