Oxford MIPAS meeting#118
22 May 07

Present

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

Instrument Status [Prev] [Next]

MIPAS currently towards the end of a standard 10day operating sequence (1 day MA, 3 days NOM, 2 days off, 2 days NOM, 2 days off)

Next few days will be used for some pointing tests (UTLS1 mode) and then 29 May - 06 June in a passive decontamination

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

April Monthly Report (CW) [Prev] [Next]

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

Summary below.

L1B Data (JH) [Prev] [Next]

L1B coverage maps updated to end of April

ftp-ops.de.envisat.esa.int now seems to have all the expected data back again.

The web-page now also shows instances of when the azimuth scanning was switched off (currently just one day: 19th March 2007)

[L1B Data Coverage]

Anomalous Scanning (AD) [Next]

From 3-11 April MIPAS seems to have been operating in an unrecognised scan pattern consisting of 22 scans from 101-37 km @ 6km intervals, with two successive sweeps (forward & reverse) at each tangent altitude. A query has been sent to ESRIN.

MORSE Update (AD) [Prev] [Next]

New version of the Oxford MIPAS retrieval code v15may07 (Web Page)

Minor modifications to allow (better) default selection of the retrieval and forward model grids.
Fix Bug#26 which could result in an infinite loop when reading .atm files without an *END file termination record.

N2O5 (JW) [Prev] [Next]

Previous MORSE retrievals never seem to reach the low values that models predict.

Usually retrieve ln(VMR) rather than VMR so a covariance of, for example, 1000% with ln(VMR) represents a variation of 0.1:10 times the a priori value, whereas with a linear retrieval it represents (1-10:1+10) = -9:11 times the a priori, ie similar probability distribution at high values but considerably different at low values

Performing a linear retrieval on simulated data shows that lower values are indeed achieved

[Plot] dashed= a priori, solid black='true' profile, red=log retrieval, blue=linear retrieval

Cloud Parameters (JH) [Prev] [Next]

Scheme to retrieve Cloud Top Height, Cloud Top Temperature and Cloud optical thickness.

Seems to work for full-resolution data, now trying it out on reduced resolution
Investigating use of SVD analysis as an alternative method of cloud detection (instead of current cloud index)

Polar Mesospheric Clouds (LMV) [Prev] [Next]

Following Manuel Lopez-Puertas presentation at the Envisat Symposium showing a radiance enhancement at high latitude between around 800-900cm-1 which may be due to the presence of PMCs

Average all spectra acquired on 19 Jul 2005 (NLC mode) above 80deg N and filter out atmospheric lines and see if a similar enhancement occurs in other regions of the MIPAS spectrum
[Plot, blue=average north of 80degN, red=south] shows no evident for peak at 84km in other bands, so if this really is a PMC, it has too small a signal at other wavelengths to allow any 'spectroscopy' using MIPAS.

Mesospheric Retrievals (LMV) [Prev] [Next]

Trying a linear least-squares fit retrieval for pT, O3 and H2O using entire MIPAS bands (screening out lines affected by non-LTE effects and gases other than CO2).

Found a bug which removes problem with the reduced resolution data.
Now trying to improve pT retrieval using hydrostatic constraint and 2nd order representation of Jacobians (ie allowing for the way that the pT Jacobians themselves change with p or T)

MIPAS/TES Retrievals (CW) [Prev] [Next]

Aim is to combine MIPAS limb measurements of stratospheric O3 with TES nadir-viewing measurements to obtain more information on tropospheric O3 profile (basically how TES was supposed to work before their problems with limb-views)

Trying to get TES nadir retrieval working: OK with simulated data but real data produces unreasonable T and H2O oscillations.
Next: look at TES team retrieval to see if running their retrieval through our forward model produces a reasonable simulation of the TES spectrum.

Oxford L2 Processing (AD) [Prev] [Next]

Starting to run MORSE retrieval to process L1B data for selected days throughout the full and reduced resolution dataset.

pT, H2O, O3, HNO3, CH4, N2O, NO2, CFC-11, CFC-12, ClONO2, N2O5 and CO (LTE assumption).

List of days processed so far
Next: working through 1 day/month of full resolution data

O3 Isotopes (CP) [Prev]

Using a Kalman filter within each latitude band for 1 day to improve S/N.

18O isotopes can be retrieved reasonably well but 17O still noisy
Initial results [Plot] suggest some variation in enrichment as a function of latitude and time (possibly both related to temperature) in agreement with one earlier study based on balloon data, but contradicting another based on ATMOS measurements

RAL Work (AW) [Prev] [Next]

Completed contributions to MIPAS O3 and T validation papers
Some investigations into T, O3 retrievals from reduced resolution mode compared with ECMWF (presented at the Envisat symposium in April)
Having another look at the RAL 2D retrieval of H2O and O3 - first trying to get it to work in 1D

ACPD Papers [Prev] [Next]

Papers selected from the ACPD website for discussion

"Geophysical validation of temperature retrieved by the ESA processor from MIPAS/ENVISAT atmospheric limb-emission measurements": M. Ridolfi et al. (published 25.04.2007, open until 20.06.2007); Introduced by LMV.
"Vertical profiles of lightning-produced NO2 enhancements in the upper troposphere observed by OSIRIS": C. Sioris et al. (published 11.04.2007, open until 06.06.2007); Comments being collected by JW.
"Global statistics of liquid water content and effective number density of water clouds over ocean derived from combined CALIPSO and MODIS measurements": Y. Hu et al. (published 28.03.2007, open until 23.05.2007); Comments submitted by JH.

Other papers with 'MIPAS' in the title in the Open Discussion phase, which may be adopted at a future meeting

"Geophysical validation of MIPAS-ENVISAT operational ozone data": U. Cortesi et al. (published 07.05.2007, open until 02.07.2007)
" Validation of MIPAS HNO3 operational data": D. Y. Wang et al. (published 17.04.2007, open until 12.06.2007)
"Bias determination and precision validation of ozone profiles from MIPAS-Envisat retrieved with the IMK-IAA processor": T. Steck et al. (published 30.03.2007, open until 25.05.2007)

Summary of the April Monthly Report (F. Niro, ESRIN)

During April 2007 the MIPAS instrument performs well, in fact only 5 anomalies were recorded due to IDU errors. Furthermore the instrument was off for about 7 hours on 2nd April due to a planned orbit control manoeuvre (see §2.2.2).
The instrument planning for the reporting month is hereafter summarized (see §2.2.1):

LOS sideways observations were planned over one full orbit on 11 and 26 April, no roll and no pitch were commanded
In-flight calibrations (IF-11, IF-6, IF-16, IF-9) were planned on 1st April
Starting from the 3rd of April the new baseline scenario with 60% duty cycle over 10 days (1 day MA+ 3 days NOM + 2 days off + 2 days NOM + 2 days off) was applied

The instrument duty cycle during the reporting month was increased to about 60%, in line with the recommendation of Science Team and industry. The availability of the instrument was high (97.3% of the planned time) owing to the very good performance of the instrument. The measurement segments not processed to L0 due to failures at the PDS were about 2.2% of the planned measurement time (see § 2.2.4).
An anomaly was detected during the daily monitoring of the level 1 products, the problem consists in a wrong radiometric calibration due to the usage of a not correct MIP_CO1_AX file. The affected products will be deleted and reprocessed at D-PAC (see §3.5.7).
The monitoring of the instrument temperatures shows an increase of about 3K over the reporting month due to the seasonal variation of the instrument temperature (see § 2.3.1).
The cooler performs really well during this month, the vibrations were always well below the warning level of 8 mg. However we start to observe a slight increase of the compressor vibrations in line with the increased instrument temperature (see § 2.3.3).
The long term trend of ADC max counts in channel A1 shows a strong correlation with the instrument self-emission and with the detector ice contamination. During the reporting month an increase of ADC max counts is observed linked to the seasonal variation (increase) of the instrument temperature (see § 2.3.4).
The 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, the observed variations are due to noise (see § 2.4.2).
The gain weekly increase during the reporting month is nominal, the maximum of gain increase in all the MIPAS bands remains well below the acceptance criterion of 1%/week (see § 2.4.3.1).
The analysis of the accumulated gain shows a steady increase of the gain with a constant rate and highlights the decontamination events throughout the mission. During the last year we observed a decreasing slope of the gain curve, showing that the detector is more and more ice-free (see § 2.4.3.2).
The absolute mispointing error is stable around a value of -30mdeg. The seasonal variations of the pointing error are small and below the fixed threshold of 8mdeg. During the reporting month no LOS calibration could be performed due to failure in the generation of level0 products at PDS or in the migsp processing (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 suggested during QWG#11 and it is reported in this MR. This analysis shows that the width of the statistical distribution of the FCE can be used as a measure of the INT performances. In fact the long term variation of the FCE statistical dispersion is highly correlated with the number of IDU velocity errors (see § 2.4.5.1).
The long term monitoring of the detected spikes is reported 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 in channels A1, A2, B1 and B2 is increasing up to Dec 2006, while since Jan 2007 we observe a decrease. 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#118 22 May 07

Oxford MIPAS meeting#118
22 May 07