Oxford MIPAS meeting#114
20 March 07

Present

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

Instrument Status [Prev] [Next]

Just completed set of Nominal mode observations, 19Mar should have been spent with 'fixed azimuth' observations (in order to establish whether or not the observed latitude variation of the altitude offset is related to an uncompensated satellite roll angle).

From April MIPAS duty cycle will be increased from 50% to 60%

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

February Monthly Report (JH) [Prev] [Next]

Noted investigations into Fringe Count errors and spike monitoring

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

Summary below.

L1 Calibration (AD)

At the previous QWG meeting it was noted that some of the lines used for spectral calibration were 'disappearing', specifically between scans during orbit 19581 (28 Nov 2005) [Map] between around 40-80degN on the ascending (nighttime - blue) part.

The Oxford pT retrieval has been run for this orbit [Plot], clearly showing an unusually cold (<200K) mid-stratosphere at these latitudes.
[Plot] showing some of the lines selected for wavelength calibration from the CO2 laser band modelled (black) for typical mid-latitude conditions, and using the retrieved pT 45degN in this particular atmosphere (red), together with the actual apodised L1C spectra (blue). Triangles show the peaks of the selected lines.
From this it is concluded that the 'disappearance' of the calibration lines is simply explained by the unusually cold stratosphere (laser band lines being particularly temperature-sensitive).

Precision Validation (CP) [Prev] [Next]

ACPD Paper discussion now closed.

Responses to referees have already been posted, now send a list of changes to the editor.

TES Radiance Comparison (CW) [Prev]

Making progress on TES-MIPAS limb radiance comparisons (having removed all the spikes from the TES data and regridded to match MIPAS)

[Plot] TES, MIPAS, MIPAS-TES

Taking another look at TES nadir retrievals to try out TES/MIPAS joint O3 profile retrieval - select cloud-free profiles from 28 Jan 05.

NOx (JW) [Prev] [Next]

Constructing monthly mean maps of NOx to examine the stratospheric variability at middle and low latitudes

Seems to be good seasonal conservation of stratospheric NOy (=NOx+HNO3) within MIPAS data - which gives some confidence in both the ESA retrieved NO2 and HNO3 products (although we don't think this has been considered as part of the NO2 or HNO3 validation).
Now considering MIPAS N2O to investigate longer timescales (conversion of N2O to NOy in stratosphere).
Main problem remains to separate local photochemical effects (converting N between various reservoirs) and transport effects (vertical and meridional).

Cloud Parameters (JH) [Prev] [Next]

Scheme to retrieve Cloud Top Height, Cloud Top Temperature and Cloud optical thickness from pair of vertically adjacent window channel radiances, plus additional information from

The retrieved clear air temperature (& dry adiabatic lapse rate)
The Cloud Effective Fraction (determined from the Cloud Index)

The retrieval problem has now been formalised into two stages: a preliminary retrieval using the 'additional information' which sets up an a priori for the main retrieval using the two radiance measurements.

Mesospheric Retrievals (LMV) [Prev] [Next]

Trying a linear least-squares fit retrieval for pT for altitudes 52, 60 and 68km using entire A band (screening out lines affected by non-LTE effects and gases other than CO2). If this works, intend to apply it to MA mode data.

Retrieving Planck function (rather than T) and pressure (rather than log(p)) gives improved results (compared to ESA L2), presumably due to improved linearity of the problem
Haven't yet resolved how to determine the best linearisation point, ie which of the 3 atmospheres or combination of atmospheres plus jacobian spectra to use. Currently retrieving with all 3 and taking best as the one which most closely predicts the observed spectra.
Added hydrostatic constraint although this appears to makes things worse with respect to agreement with ESA L2 data - not understood.

RAL Work (AW) [Prev] [Next]

Working on the final version of the MIPAS pT validation paper.

ACPD Papers [Prev] [Next]

Papers selected from the ACPD website for discussion

"Retrieval of temperature profiles from CHAMP for climate monitoring: intercomparison with Envisat MIPAS and GOMOS and different atmospheric analyses": A. Gobiet et al. (published 27.02.2007, open until 24.04.2007); Introduced by CP.
"Validation of MIPAS-ENVISAT NO2 operational data": G. Wetzel et al. (published 02.03.2007, open until 27.04.2007); Comments being collected by CW.
"Global peroxyacetyl nitrate (PAN) retrieval in the upper troposphere from limb emission spectra of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS)": N. Glatthor et al. (published 29.01.2007, open until 26.03.2007); Comments being collected by LMV.
"HDO measurements with MIPAS": J. Steinwagner et al. (published 19.01.2007, discussion now closed); Comments submitted by AD.
"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, discussion now closed); Comments submitted by JW.

There are currently no other papers with 'MIPAS' in the title in the Open Discussion phase.

Summary of the February Monthly Report, F. Niro (ESRIN) 13 Mar 2007.

During February 2007 the MIPAS instrument performs extremely well, in fact we report only two instrument failures due to IDU errors and one unavailability due to a SPE processing timeout, this latter anomaly is a known problem and it was already seen on Dec 2003 (see §2.2.2).

The instrument planning for the reporting month is hereafter summarized (see §2.2.1):

The instrument operates with the baseline planning (2*3 days NOM + 2*3 days UTLS1 measurement segments)
Duty cycle was planned to around 50% (3.5-days ON, 3.5-days OFF)
IDU re-initialization was set every 3 orbits

The instrument duty cycle during the reporting month was 48.10%, in line with the recommendation of Science Team and industry. The availability of the instrument was high (92.2% 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 10% of the planned measurement time (see § 2.2.4).

The monthly monitoring of the instrument temperatures shows a steady situation. Temperature variations are within 1-2K over the entire month. However a big jump of about 5K in the CBB and FCA temperature was detected after the SPE anomaly of 6th February. This problem was already observed after a platform switch-off, it is a well known anomaly and it is due to the fact that for a short period after the switch-on, the BB survival heater stays on (see § 2.3.1).

The cooler perform really well during this month, the vibrations being always well below the warning level of 8 mg (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 decontamination events. During the reporting month a slight decrease of ADC max counts is observed linked to the seasonal variation of 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, furthermore the variations are mostly 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% (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 events throughout the mission. During the last months 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 -25mdeg. The seasonal variations of the pointing error are small and below the fixed threshold of 8mdeg. During the reporting period the computed mispointing is about -30mdeg (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 on 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#114 20 March 07

Oxford MIPAS meeting#114
20 March 07