Oxford MIPAS meeting#110
23 January 07

Present

Oxford: Anu Dudhia, Michael Holmes, Jane Hurley, Luis Millan-Valle, Chiara Piccolo, Joanne Walker, Claire Waymark
RAL: Alison Waterfall

Instrument Status [Prev] [Next]

Working normally, although probably switched off at the moment due to Envisat orbital control manoeuvre (scheduled for 22/23 Jan).

Mission Planning Document for 2007 [XLS] [HTML].
Currently defined measurement modes
Envisat Web-Site

December Monthly Report (AD) [Prev] [Next]

MIPAS monthly report for December is now available [Summary]

Full report downloadable from http://earth.esa.int/pcs/envisat/mipas/reports/monthly/

L1B Data (JH) [Prev] [Next]

L1B data downloaded up to end of 2006 and coverage maps updated

[L1B Data Coverage]

Precision Validation (CP) [Prev] [Next]

Using comparisons of pairs of MIPAS retrievals at locations where orbits intersect to see how the observed standard deviation compares with the predicted variability from the retrieval covariance.

Paper now on the ACPD web-site

O3 Isotopes (CP) [Prev] [Next]

Reselecting microwindows for O3 isotopic retrievals [Plot] to see if S/N can be improved by joint retrieval of all isotopes together plus Kalman filter.

TES Radiance Comparisons (CW) [Prev] [Next]

Continuing with comparison of MIPAS and TES limb radiance spectra from Jan 28 2005 using regions where the MIPAS bands and TES filters overlap.

Just using SD of averaged highest altitude TES spectra seems to be a reasonable method for finding extra spikes not flagged by the TES L1 processing
Plan to convert TES limb spectra (sampled at 0.06cm-1) to MIPAS RR spectra (sampled at 0.0625cm-1) via fourier transform, but not quite so straightforward since the TES spectral grid does not start at an integer multiple of 0.06cm-1, (652cm-1 instead of 652.02cm-1) so will interpolate TES spectra to 0.01cm-1 grid before applying FT (we think this is the only solution, but we're not experts!)

CO Isotopes (JW) [Prev] [Next]

Analysing MIPAS averaged day/night spectra to investigate behaviour of CO isotopomers 28 & 36.

Require absolute amplitudes of isotopic lines, which requires excluding other contributions.
Currently trying a simple least squares fit of CO2 and O3 spectra to remove local 'background' features [Plot]

Cloud Parameters (JH) [Prev] [Next]

Attempting to retrieve Cloud Top Height, Cloud Extinction and/or cloud top temperature using a pair of adjacent sweeps (the cloud top being in the FOV of the upper sweep) and a single microwindow 960-961cm-1 (most transparent region of MIPAS spectrum)

Problems with convergence were due to numerical convolution with FOV function: radiance did not increase smoothly with cloud-top height, hence Jacobians (calculated from finite difference) caused solution to oscillate - now fixed.
Note that there may be more than one solution for any pair of measurements since radiance is not a monotonic function of Cloud extinction: thin cloud tends to zero radiance, thick cloud tends to Planck radiance for (low) Cloud Top Temperature, but intermediate thickness gives Planck radiance for penetration towards tangent point which is warmer than the Cloud Top Temperature.
Next: try with real data

Mesospheric Temperatures (LMV) [Prev] [Next]

Attempting a linear temperature retrieval from mesospheric spectra. Using mid-latitude day-time conditions for a reference spectrum (=initial guess) and jacobians.

Now using a 3-level 'global fit' retrieval instead of independent retrievals for each level
[Plot] (lower panel) shows reasonable agreement with CIRA (top panel) and MIPAS L2 data (2nd page) but still retrieving high temperatures in polar summer stratopause.
Next: try to refine masks to remove spectral points that may be affected by non-LTE

Aircraft Emission Mode (AD/MH) [Prev] [Next]

New AE mode measurements were taken on [26Dec06], [27Dec06], [28Dec06], [29Dec06]

Unlike May05 data, these are incorporated into normal L1B files:
However, an initial analysis suggests that these still suffer from the same problems, i.e.
- L1B engineering altitudes approx. 2km lower than planned altitudes (5, 6.5 ...km instead of 7, 8.5 ...km)
- Actual tangent points (judging by retrieved tangent pressure) approx. 5km higher than engineering alitudes (10,11.5 ... km)

Michael Holmes is an MPhys whose project this term is to try to detect aircraft signatures in MIPAS spectra. Currently running the RFM to simulate MIPAS spectra and perturbations of NO2, O3, HNO3, NO and CO - the main gases thought to be perturbed by aircraft emissions.

ACPD Papers [Prev] [Next]

Papers selected from the ACPD website for discussion

" Three years of global carbon monoxide from SCIAMACHY: comparison with MOPITT and first results related to the detection of enhanced CO over cities": M. Buchwitz et all. (published 11.1.07, open until 08.03.2007); Introduced by JW.
" A twenty-year study on natural and manmade global interannual fluctuations of cirrus cloud cover": K. Eleftheratos et al. (published 05.01.07, open until 02.03.07); Comments being collected by JH
" Solar cycle variations of stratospheric ozone and temperature in simulations of a coupled chemistry-climate model ": by J. Austin et al. (published 27.11.06, now closed); Comments were collected by CW but she just missed the deadline for submitting them to the discussion.
"Assimilation of TES CO into a global CTM: first results": N. A. D. Richards et al. (published 22.11.06, now closed); Comments submitted by CP.
"MIPAS Level 1B algorithms overview: operational processing and characterization": A.Kleinert et al. (published 26.10.2006, now closed); Comments submitted by LMV.

There are other MIPAS-related papers currently open (which may be adopted for group discussion in future meetings)

"HDO measurements with MIPAS": J. Steinwagner et al. (published 19.01.2007, open until 16.03.2007)
" Precision validation of MIPAS-Envisat products": C. Piccolo & A. Dudhia (published 18.01.2007, open until 15.03.2007) - OK, we're not going to discuss this one!
" Technical Note: Regularization performances with the error consistency method in the case of retrieved atmospheric profiles": S. Ceccherini et al. (published 18.12.06, open until 12.02.07)
" Characterization of MIPAS elevation pointing": M. Kiefer et al. (published 13.12.06, open until 07.02.07)
" The Assimilation of Envisat data (ASSET) project: by W. A. Lahoz et al. (published 8.12.06, open until 02.02.07)

Summary of December 2006 Monthly Report (F.Niro, ESRIN)

During December 2006 the MIPAS instrument performs extremely well, in fact only 4 unavailabilities were observed due to IDU errors.

MIPAS was not operational from 28th November to 1st December due to an unexpected and urgent maintenance activity on one of the ENVISAT on-board memory. Another anomaly occurred on ENVISAT on 12 December, resulting in the interruption of the measurements of all the payload instruments. The anomaly was most likely caused by a flux of heavy charged particles originating from a high peak of solar activity. As a result MIPAS measurements were stopped during 12 - 19 December.

The instrument planning for the reporting month is hereafter summarized:

The instrument operates in support to ECMWF campaign during 1 - 11 December (2 orbits ON - 3 orbits OFF)
In flight calibrations (IF-9, IF-10, IF-11, IF-16) were planned on 14 December
MA-UA observations were planned during 19 - 22 December
Observations in Aircraft Emissions (AE) mode were planned during 27 - 29 December

All the planned measurements were acquired, but the IF calibrations were lost due to the platform switch-off occurred on 12 December, as a result the same IF calibration were replanned for the beginning of January 2007.

The instrument duty cycle during the reporting month was 36%, in line with the recommendation of Science Team and industry. The availability of the instrument was high (97% of the planned time) owing to the very good performance of the INT. The measurement segments not processed to L0 due to failures at the PDS were about 3.5% of the planned measurement time (see § 2.2.4).

The monthly monitoring of the instrument temperatures shows a steady situation. Temperature variations are within 1K over the entire month, however a strong jump of the CBB temperature was recorded after the PLSOL occurred at the end of November 2006. This problem is well known (see April 2006 MR) and is due to the fact that for a short period after the switch-on the BB survival heater stays on. The anomaly was resolved in few hours without affecting the data quality (see § 2.3.1).

The long term monitoring of ADC max counts in channel A1 shows a strong correlation with the instrument self-emission and with the decontamination events. During the reporting month the decontamination induced by the PLSOL of 28 November determines an increase of the ADC max counts in channel A1 (see § 2.3.2).

The cooler perform really well during this month, the vibrations being always well below the warning level of 8 mg (see § 2.3.3.1).

The long term monitoring of the spectral correction factor shows a stable situation since the variations are of the order of 3 ppm over almost two years of operations (see § 2.4.2).

The gain weekly increase during the reporting month is nominal, the maximum of gain increase in the band A remains well below the acceptance criterion of 1%. In addition the PLSOL occurred at the end of November 2006 caused a decrease of gain in the band A by almost 3.4% (see § 2.4.3.1).

The analysis of the accumulated gain shows a slow increase of the gain with a constant rate and highlights the decontamination effect induced by the platform switch off of 28 November (see § 2.4.3.2).

The absolute mispointing error is stable around a value of -20mdeg, the seasonal variation of the pointing error are small and below the fixed threshold of 8mdeg. During the reporting period only one LOS calibration was performed, since two planned LOS calibrations were lost due to the ENVISAT switch-off (12 - 18 December) and to a failure in the L0 production at the PDS (see § 2.4.4).

The long term monitoring of fringe count errors (FCE) for the RR mission was investigated this month. A statistical analysis was proposed during QWG#11 and is going to be implemented, results will be presented in the next MR after verification and consolidation of this new approach (see § 2.4.5.1).

The long term monitoring of the detected spikes is presented in this MR. The presence of spikes on the scene IGM is detected by the L1 processor, these spikes are corrected in order to avoid artefacts in the spectrum. The number of spikes seems to slightly increase since June 2006 in channels A1, A2, B1 and B2. The channels C and D (the detector most affected by spikes) didn't show any trend so far (see § 2.4.5.2).

The level 0 NRT daily reports can be accessed at the following address: http://earth.esa.int/pcs/envisat/mipas/reports/daily/Level_0_NRT/
The level 1b OFL daily reports can be accessed at the following address: http://earth.esa.int/pcs/envisat/mipas/reports/daily/Level_1_OFL/

Oxford MIPAS meeting#110 23 January 07

Oxford MIPAS meeting#110
23 January 07