Oxford MIPAS meeting#23
21 Jan 03

Present

Oxford: Alastair Burgess, Anu Dudhia, Don Grainger, Vivienne Payne, Chiara Piccolo, Clive Rodgers
RAL: Victoria Jay, Martin Juckes

Instrument Status [Prev] [Next]

Operating normally as far as we know, although no L2 data received since 17th January.

L2 Data (CP) [Prev] [Next]

In /home/crun/eodg/mipas/L2/ [Plots of profile locations]

111 days received so far, up until 17th January

L1 Data (AD) [Prev] [Next]

In /home/crun/eodg/mipas/L1B/

Roberta Mantovani (ESRIN) has delivered a new version of Orbit 2081 reprocessed to try and remove gain oscillation in the non-linearity correction

L1_2081_NewNLCoef

Occupation Matrices (CP) [Prev] [Next]

Occupation Matrix Analysis

Retrieval	No.Profiles	Nominal OM
pT	62493	96.6 %
H2O	54513	95.2 %
O3	59649	95.4 %
HNO3	60737	96.6 %
CH4	50752	87.5 %
N2O	57355	95.1 %
NO2	63027	98.1 %

Nominal OMs being used >95% of retrievals apart from CH4 (which uses OM 312 4.6% of the time, ie missing C-band at 12km)
Still detecting unidentifiable OMs in 0.3% of cases, ie cannot relate MWs/Sweeps listed in L2 data to list of delivered OMs - explanation?
Appear to be more NO2 profiles than pT profiles - explanation? [Next]

Auxiliary Data Updates (AD/CP) [Prev] [Next]

New data in /home/crun/eodg/mipas

/hitran [Prev]
- IMK have detected missing HNO3 lines between 880-885cm^-1 in pf3.0 [Plot]
- This lies between the two nominal HNO3 microwindows HNO30001 (876.375-879.375cm^-1) and HNO30006 (885.100-888.100cm^-1) but line wing effects would not have been included in the in-flight LUTs.
- Corrected version hitran_mipas_pf3.1
/rfm/rfm_files/
- RFM binary file hitran_mipas.bin now updated to represent pf3.1
/MW/, /CS/, /grd/
- New microwindow database MW_SO2_104.DAT, LUTs and irregular grid data for SO2 microwindows.

OPTIMO (VP/AD) [Prev] [Next]

Optimising RFM modules within Oxford retrieval code to try an speed up processing

Original CPU usage for a pT retrieval (compile with -p option, then run prof)

%time     seconds  cum %   cum sec  procedure (file)
 49.6    163.5137   49.6    163.51 rfmray_ (rfm/rfmray.for)
 15.4     50.6172   65.0    214.13 radtra_ (rfm/radtra.for)
 12.1     39.8809   77.1    254.01 rfmils_ (rfm/rfmils.for)
 11.7     38.6074   88.8    292.62 rfmlut_ (rfm/rfmlut.for)

After optimising rfmray (ray tracing) and rfmils (AILS convolution) ...

 38.0    463.1885   38.0    463.19 rfmlut_ (rfm/rfmlut.for)
 35.7    435.7119   73.7    898.90 radtra_ (rfm/radtra.for)
  9.2    112.6865   82.9   1011.59 rfmray_ (rfm/rfmray.for)
  6.7     81.3555   89.6   1092.94 rfmils_ (rfm/rfmils.for)

rfmlut interpolates absorption coefficients from SVD-compressed Look-Up tables
radtra integrates the radiative transfer equation along the ray path

It appears that a 50% improvement in speed has been obtained so far

H2O Bias (VP) [Prev]

Using Profile#68 from Orbit 2081 (AMIL2DA mid-lat nighttime case), verified that climatological H2O predicts lower radiances than observed in L1B spectrum H2O Microwindows.

Next: generate full spectrum from retrieved profiles for this location and compare with L1B.

Spectral Shift (VP/CP) [Prev]

Since the residual spectral shift in MIPAS retrievals appears fairly stable with time, for local processing a simple linear correction will be applied to the position of the AILS functions for each microwindow

Residual shift in ESTEC data, Orbit 2081 (y-axis in units of 0.001cm^-1)
Fitted straight line correction (y-axis in units of cm^-1)

This correction has been applied in Oxford L2 preprocessing routine ilspar.pro.

Difference in AILS between ilspar and ML2PP (original): [H2O_0001] (1650.025-1653.025cm^-1) [H2O_0002] (807.850-808.540cm^-1) [H2O_0007] (1645.525-1646.200cm^-1)
Difference in AILS between shifted ilspar and original ilspar: [H2O_0001] (1650.025-1653.025cm^-1) [H2O_0002] (807.850-808.540cm^-1) [H2O_0007] (1645.525-1646.200cm^-1)

Next: rerun OPTIMO and confirm that spectral shift v wavelength has been eliminated (still leaves unexplained variation with altitude).

Data Assimilation (MJ/CP) [Prev] [Next]

Assimilating MIPAS O3 and H2O in an isentropic model

Original plan was to use GOMOS O3 as an independent validation, but status of GOMOS O3 product uncertain (CP to check with ECMWF who have also been looking at GOMOS O3)
Current plan is to obtain GOME O3 profile data retrieved at RAL, but this is subject to RAL having sufficient computers/people available to process the necessary data

JAS Special issue planned on the Antarctic stratospheric warming of 2002, may submit something involving MIPAS data.

SO2 Retrievals (AB/AD) [Next]

(AB) Using OPTIMO to retrieve SO2 profiles

pT and SO2 profiles retrieved down to 6km, but assuming climatological H2O at the moment (next: retrieve H2O also)
Using orbits 3489,3490 (30th October), SO2 enhancement detected from Mt Etna (as observed in MERIS and SCIAMACHY data at the Envisat Validation Workshop)
Plot of Level 1 Radiances within Etna plume showing evidence of SO2 features in MIPAS spectra.
Plot of Retrievals within and outside Etna plume showing enhanced SO2.
Enhancement most evident at 9km rather than 6km, and undetectable at 12km
Also retrieves higher SO2 than climatology in the mid-stratosphere

(AD) Using REC analysis on ESA L2 residuals averaged by month and 6 latitude bands (dictated by occupation matrices) to fit SO2 signatures in operational microwindows for all species at each altitude - a very crude 1st order retrieval (same technique used to estimate H2O bias from non-H2O microwindows in previous meeting)

[Results]

Different panels for each latitude band, 006 is 65-90N, 001 is 65-90S
Different line styles for each month's averaged residuals
y-axis is altitude 12-42km
x-axis is %deviation of SO2 from assumed climatology (zero deviation corresponding to zero SO2 signature in residuals)

Note the following features:

July data generally anomalous (generally true of all July REC analyses) and can probably be ignored
Northern latitudes exhibit a significant trend of 5-10% decrease per month at low altitude, which seems unreasonably large (also evident to a lesser extent in southern latitudes, so probably not seasonal)
Significantly less SO2 in stratosphere than climatology, contradicting conclusion from profile retrievals

Minor Species (AD) [Prev] [Next]

Microwindows have been selected for all species which might be detectable in MIPAS using an ORM-like algorithm ...

Local Thermodynamic Equilibrium (CO and NO therefore excluded)
Finite number of microwindows, limited to Min(10 MWs or 10 000 measurement)
Simultaneous fit of continuum in each microwindow
one profile per limb scan
retrieval range 6-68km

Table shows Shannon Information Content of retrieval in bits (0 corresponds to 100% uncorrelated uncertainty in a priori knowledge at each altitude level) using the most recent error estimates

Molecule	Info	Molecule	Info	Molecule	Info
CFC-12	36.2	HCN	19.2	HOCl	12.7
CFC-14	33.1	COF2	18.8	SO2	8.6
ClONO2	25.0	OCS	15.2	H2O2	8.2
CFC-11	23.7	SF6	15.0	ClO	5.3
CFC-22	23.6	N2O5	13.5	CCl4	3.8
NH3	20.2	C2H6	13.3

Most estimates based on a mid-latitude daytime profile, but polar winter used for ClO and HOCL, and mid-latitude night for N2O5 and ClONO2 (since significantly higher concentrations are expected for these situations).
Also looked at C2H2 and HNO4, but no microwindows were found.

Retrieval Non-Linearity (CR/CP) [Next]

Examining the effect of non-linearity on retrieval convergence and use of singular vectors

EGS/AGU/EUG Meeting Nice 6-11 April 2003 [Next]

Known MIPAS-related UK abstracts submitted are

A. Dudhia et al, detection of minor species in MIPAS spectra
A. Burgess et al, detection of SO2 in MIPAS spectra
RAL, combination of MIPAS/SCIAMACHY data
G. Ewen et al, Effects of clouds on limb radiative transfer in the infrared
M. Juckes et al, MIPAS data assimilation
C. Rodgers et al, Non-linearity in retrievals
J. Remedios et al, Observations of Clouds by the MIPAS instrument on Envisat
R. Spang et al, the Temporal and Spatial Evolution of the PSC Distribution in the Arctic Winter 2002/2003 as observed by MIPAS on ENVISAT
G. Allen et al, an Investigation of the Potential Retrieval of Peroxyacetyl Nitrate (PAN) from the MIPAS Spectral Dataset
D. Moore et al, Validation of Methane and Nitrous Oxide data products from the MIPAS Instrument on ENVISAT
D. Moore et al, the Potential for Measuring HCFC-22 from the MIPAS Instrument

Oxford MIPAS meeting#23 21 Jan 03

Oxford MIPAS meeting#23
21 Jan 03