Oxford MIPAS meeting#39
16 Sep 03

Present

Oxford: Anu Dudhia, Don Grainger, Chiara Piccolo, Analia Quijano
RAL: Victoria Jay
NASA/Langley: Javier Martin-Torres (visiting)

Instrument Status [Prev] [Next] (Some details on the Envisat Web-Site)

Envisat payload shutdown occurred on 4th Sep 22:52 UTC
MIPAS nominal mode resumed on 8th Sep

L1 Data [Prev] [Next]

Note that correction to ILS parameters in L1B data has not yet been implemented by ESA in the operational processing.

L2 Data [Prev] [Next]

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

Data received up until 15th September, plotted up until 13th September.
Some L2 data has now been retrieved for every day since 8th September, 7 days of continous operation.
Software version 4.59 in use since 23 Jul 2003.
Problem noted in data from 8 Sep onwards (see below)

Systematic Change in L2 Profiles

Dominique Fonteyn (BIRA) (email 15 Sep 03) reports systematic differences in L2 products, especially CH4, N2O and HNO3, after MIPAS operations resumed on 8th Sep.

CH4 zonal mean cross sections before and after switch off.

Antje Dethof (ECMWF) has also noticed (email 16 Sep 03): "Looking at our MIPAS monitoring statistics for this month I noticed that after the instrument came back on 8 September there is a pronounced change in the MIPAS temperatures (about 5K in the global mean), giving a worse fit to the ECMWF temperature analysis than before. We also see changes in the ozone and water vapour fields."

Time series of global means: TEM, O3, H2O

Zonal mean profiles confirm that all species show decreases of ~10%, more for short wavelengths (H2O,NO2), less for long wavelengths (HNO3, O3), but temperature shows increase of a few K (consistent with ECMWF observations)

Ignore subtitles - solid symbols are averages from 8/9 Sep, open symbols from 1-4 Sep:
[CH4] [H2O] [HNO3] [N2O] [NO2] [O3] [TEM]
Further details on plots.

Problem in species concentrations can be explained by increase in retrieved temperatures, but why are temperatures suddenly 5K higher?

Rob Koopman notes that there had not been a radiometric gain calibration since original switch off - currently the most likely explanation
No significant change in reported tangent altitude or retrieved pressure, so purely temperature effect
Occupation Matrix Statistics for 8/9 Sep show no significant change compared with August data, so change cannot be explained by using different microwindows for pT retrieval.

A further question is whether the profiles subsequently recovered - zonal means only plotted up to 9th Sep but ECMWF plots suggest problem continues at least until 15th Sep.

Saharan Dust (AQ)

Recent workshop on atmospheric dust noted that Saharan dust has occasionally been detected over the Mediterranean to altitudes >10km from ground-based observations. Trying to find observations with coincident MIPAS spectra to look for distinctive dust signatures in the continuum.

OPTIMO Retrievals (CP) [Prev] [Next]

Using the Oxford processor to retrieve MIPAS pT, O3 and H2O profile data during the split Antarctic vortex period, 8Sep- mid-October.

Orbital Plots show continued `chequerboard' pattern linked to L1 gain oscillations arising from the radiometric non-linearity correction - need to apply more regularisation to remove this
Chi Square Statistics - possible diagnostic for screening out `bad' retrievals.

Joint pT, O3, H2O Microwindows (AD) [Next]

Currently in the process of selecting sets of microwindows of 1cm^-1, 2cm^-1 and 3cm^-1 max width for global, joint retrievals.
3cm^-1 is the current MIPAS maximum width but narrower microwindows have been requested for testing purposes.
LUTs and irregular grids to follow once selection is completed (before next meeting, hopefully)

AMIL2DA [Prev] [Next]

JGR Blind Test Retrieval Intercomparison paper - Responses to referees comments now ready. Thomas von Clarmann would like everyone to check what he's written as soon as possible before he sends them off.

REC Analysis [Prev] [Next]

Analyses for August 2003 now complete.
No major changes in August data compated to July
New plots now added, showing often substantial differences between residual signatures obtained in target and non-target microwindows.

Oxford MIPAS meeting#39 16 Sep 03

Oxford MIPAS meeting#39
16 Sep 03