Oxford MIPAS meeting#45
09 Dec 03

• Data received up until 8th December, plotted up until 30th November.
• Some L2 data has now been retrieved for every day since 6th December, 2 days of operation.
• Software version 4.59 in use since 23 Jul 2003.

• /MW/ Microwindow Databases
  • All MWs now stored here, including CO and joint pT+H2O+O3 microwindows.

• Anomalous values since switch-on (6th December) - temperatures a couple of K higher and VMRs ~10% lower than before.
• Presumably a repeat of the problem in early September with the detectors warming during switch-off and reducing ice contamination but the NRT retrievals still using the old gain calibration.
• Email from Antje Dethof (ECMWF) 8th Dec:

  Dear all, MIPAS data show a small offset again after the recent pay-load switch-off, similar to what was seen between 8-17 September, even though the offset isn't as large this time. Has a gain calibration been carried out since MIPAS came back? I've attached 3 plots, showing timeseries of data up to 0z today: [TEM] [H2O] [O3]

• Response from Rob Koopman (ESRIN) 8th Dec:

  Thanks for the warning. Indeed gain calibration for data after the switch off can only be performed tomorrow, and all NRT data until then are degraded. The dissemination tomorrow will arrive well in time at the D-PAC to avoid any impact on OFL data. The modifications to the MICAL calibration environment that are currently being finalised are aimed at avoiding such long invalid periods in NRT data, and are expected to be completed before the end of this year.

On 27-29 NOV 2003 there is a phase error problem with spectra of limb-scans south of about 60S resembling the problem of January 2003. (see orange/red color in appended cloudmap and plot of spectra.)

• Causing OPTIMO problems also, specifically some low altitude sweeps are being assigned pressures which do not increase monotonically with elevation angle (more likely to be a problem with cloud detection?)

• Monthly Means
• OM Statistics
• REC Analyses

• Instrument Performance
  • D1 detector has became very noisy on 5th Oct 03, possibly associated with mispointing and viewing Earth
  • Two types of pointing anomaly have been noted
    • Daily jumps due to upload of orbital parameters (Note: should be eliminated from 10th Dec with new algorithm)
    • Annual cycle in pointing offset due (?) to inconsistent usage of coordinate systems.
    The 3-4 day altitude oscillation is probably an aliasing effect of the first anomaly: the orbital period of 101 minutes gives 14.257 orbits per day, so each daily mean contains some fraction of the orbit with the updated pointing which repeats every 3-4 days
  • Pointing-jitter in the IF16 (full interferogram mode) data should appear in the spectra as ghost lines at +/-13.5cm-1 with amplitudes of the order of 0.5% varying randomly from spectrum to spectrum.
  • Impact of the variations in interferometer slide velocity but the effect on the retrievals appears negligible.
• Instrument Operations
  • Nominal operating mode:
    • 72 scans per day
    • Deep space view every 5 scans
    • `Special Event Mode' (SEM) lasting 29 seconds once per orbit (basically covering time required to resynchronise scan with latitude) includes two high spectral sampling scans
    • Line of Sight (LOS) calibration once per week (usually Saturday), two consecutive orbits in case one is missed
    • Radiometric Gain Calibration (RGC) once every 14 orbits, lasting 1040seconds. From 7 Jan 2004 this will be reduced to twice/week.
    • Special Modes: Table shows originally specified modes along with the orbit numbers/dates presented at the QWG meeting. Actual observation details may have been different, eg S3/S4 were slightly modified at high altitude to avoid elevation steps bigger than 4.5km (temporary fix).

      Mode	Description	Alt. Range	Vert. Resl	Spec. Resl	Orbits	Date
      S1	Polar Chem. & Dynam.	7-55 km	2 km	0.025 cm-1	6675-6680	10JUN03
      S2	Trop/Strat Exchange	5-40 km	1.5 km	0.025 cm-1	6681-6689	10-11JUN03
      S3	Aircraft Emissions	6-40 km	1.5 km	0.025 cm-1	9318-9324	12DEC03
      S4	Stratospheric Dynamics	8-53 km	3 km	0.1 cm-1	9325-9325	12DEC03
      S5	Diurnal Changes	15-60 km	3 km	0.025 cm-1	9300-9300	10DEC03
      S6	Upper Trop/Lower Strat	6-35 km	2 km	0.1 cm-1	6590-6601	04-05JUN03
      					7020-7035	04-05JUL03

• Level 1B
  • Last change was 3 Nov 03 (to auxiliary data, not software)
  • Current status: 4 coadditions for spectral calibration, 10 coadditions for ILS calibration.
  • Data from 6 Jul 02 - 18 Nov 03 will be reprocessed with current configuration
  • NESR from in-flight temperatures of 219-223K
  • Phase is very stable
  • ILS is also stable - can we assume fixed parameters?
  • LOS pointing - correction of 25mdeg (approx 1km) built into commanding (which is presumably why most L1/L2 tangent point altitudes are ~1km higher than nominal).
  • IMK retrievals show almost constant offset in MIPAS altitudes with respect to ECMWF altitudes
  • DLR non-linearity correction results in reduction of retrieved temperatures by 1K for orbit 2081.
  • IAA note small (few nW at 800cm-1) radiometric offset at high altitudes, which also appears to alternate with sweep (residual problem with forward/backward sweep calibrations?)
• Level 2
  • Web-site http://envisat.esa.int/instruments/availability/ gives full list of periods of unavailability for each instrument
  • Web-site http://envisat.esa.int/dataproducts/availability/ gives current status of the data products for each instrument
  • Current product anomalies
    • Daily pitch jump
    • Noisy p,T (possibly) since October ?
    • Cloud detection not working as expected
    • 28 Oct 03 Change in high altitude/high latitude T, H2O, O3, probably related to solar storm
    • Problem in L1/L2 processing on 29 Oct 03 also due to solar storm
    • Off-line processor takes more CPU time than expected
    • Missing NESR data for Special Modes
  • Oxford: [Powerpoint presentation].
    • Comparisons of monthly means Nov03 and Nov02 show fairly stable retrieval - main problems/differences are
      • Anomalous spectral derivative residuals in NO2 microwindows
      • Persistent equatorial anomaly at 12/15km CH4, N2O
      • Increase in HNO3 of the order of 10% since 23rd July 2003 (associated with update of spectroscopic data)
      • Decrease of a few percent in trace gases since 3rd November 2003
    • Large differences (up to 70K) in Nov 03 polar temperatures compared to IG climatology is due to the IG temperature profiles applied in November being the same as July, taken from the MIPAS Polar SUM and WIN profiles - ie, the IG polar temperature profiles being used in November (and December) are based on July conditions.
  • Cloud detection: for low altitudes (6km, 9km) may need to introduce a more sophisticated algorithm for distinguishing high water vapour from cloud
  • Noctilucent clouds evident in Jul 02 data near polar summer mesopause