Oxford MIPAS meeting#41
14 Oct 03

Present

Oxford: Alastair Burgess, Anu Dudhia, Vivienne Payne, Analia Quijano
RAL: Victoria Jay, Martin Juckes

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

Normal operations
Shut down for a few hours expected on Oct 28th when a satellite out-of-plane manoeuvre is scheduled

L1 Data [Prev] [Next]

According to Frank Hase (IMK), correction to ILS parameters in L1B data was implemented on 4th October, there may be some signature in residuals (although no obvious change in daily means) [Rob Koopman has subsequently informed us that no change was made]

L2 Data [Prev] [Next]

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

Data received up until 13th October, plotted up until 30th September.
Some L2 data has now been retrieved for every day since 20th September, 24 days of continous operation.
Software version 4.59 in use since 23 Jul 2003.
[Comments about off-line processor removed at Rob Koopman's request]
Cal/Val data being reprocessed with same configuration (extended altitude range) as offline retrievals using a separate stand-alone processor at ESRIN. Aim is to complete reprocessing of MIPAS Cal/Val data (about 20% entire dataset) by next March.

30km Zonal Mean Traces (AD) [Prev] [Next]

NRT data for the past couple of days is generally incomplete so conclusions may change after a couple of days as more data is included

Altitude (Note that the altitudes plotted are the corrected altitudes in the L2 data, not the L1 altitudes). Large variations in recent data, especially S.Polar
Pressure Recent downward trend in N.hem has levelled out, S.polar starting to rise rapidly. No explanation of 3-day oscillations yet.
Temperature N.Polar and N.Mid Lat continue to drop, S.Polar rising, others constant
CH4 Sharp increase in last few days at low latitudes and N.Midlat, also S.Polar but with large variability
H2O Increase in last few days in low and mid lats, and possibly N.Polar
HNO3 S.Polar continues to drop, no obvious trend at other latitudes
N2O Rise at low latitudes and N.Mid lats, also S.Polar (similar to CH4)
NO2 Some oscillation in N.hem in recent days but no obvious trend
O3 Last few days show increase in N.hem and S.low latitudes, S.polar continues recent decline after peaking on 6th Oct. S.Mid Lat remains constant

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

Selection of top 10 1cm^-1 wide microwindows now complete. Look-Up Tables and Irregular grids also generated.

1cm^-1 10MWs, 4223pts, 190 bits [MW Locations]
Separate Retrievals 14 MWs, 8177 pts, 158 bits. [MW Locations]

2cm^-1 and 3cm^-1 MWs still in progress

Occupation Matrix Statistics [Prev] [Next]

Statistics for September 2003 now generated, with comments

Data Assimilation (MJ) [Prev] [Next]

Produced statistics for April 2003 for MIPAS assimilated O3 compared to SBUV, POAM3, HALOE and SAGE3 for different isentropic surfaces

HALOE generally 5% lower than MIPAS
SAGE 3 generally 5% higher than MIPAS

Future work

Include ozone sonde data for further validation
Get hold of ILAS 2 data, especially for CH4
Run analyses for GOMOS rather than MIPAS

REC Analyses [Prev] [Next]

Plot REC analyses for signatures of contaminant species

NH3 Up to May 2003 analyses suggest NH3 is overestimated by an order of magnitude, but from July 2003 onwards NH3 appears to be underestimated at 21km. Unlikely to be a change in atmospheric NH3, more likely a change in spectral signature in a microwindow region sensitive to NH3 signal.
SO2 Generally consistent overestimate of atmospheric SO2 above 30km, although Apr-Jul 03 suggests an underestimate in N.hem, especially polar latitudes, at 30km. Again, unlikely to be a real change in atmospheric SO2. [Next]

Monthly Mean Data [Prev] [Next]

Monthly Mean data for September 2003 now plotted (excludes 8-19 Sep when there were gain calibration problems)

Altitude (AD)
- Changes from previous month generally <100m
Temperature (AD)
- S.Polar and Mid Latitude regions warming by up to 10K compared to previous month below 50km, cooling above.
- N.Polar region cooling by up to 10K compared to previous month
- Low latitude profiles continue approx 10K cooler than initial guess climatology at 40km
Pressure (AD)
- N.hemisphere and equatorial pressures reduced by 10-20% compared to previous month
- S.Polar pressures increased by 10-15% above 21km, reduced by a few % below
- S.Mid Latitude pressures increased by a few % above 36km, reduced by up to 10% below
- Pressure in polar regions now departs from IG climatology by >40% at high altitudes (S.Polar is lower, N.Polar is higher), while converging to within 10% for other latitudes
CH4 (VP)
- The equatorial profiles show a strange shape, with a local minimum at 15km. This has been the case since July. (From January to June, there was a strange minimum visible at 18km).
- It was suggested that the change in this feature could have been brought about by the implementation of cloud detection in the processor in July(?).
- Values in the northern mid-latitude and polar profiles are slightly lower than last month.
H2O (VP)
- The southern polar profile is a strange shape, being around 1.2ppmv lower than the IG profile at 18km. However, the shape is consistent with last month's profile.
- It was suggested that this may be due to dehydration within the polar vortex.
2CH4+H2O (VP)
- Profiles of this quantity are somewhat higher than would be expected from climatology (around 1ppmv upwards of 21km).
- This is in keeping with profiles from previous months.
HNO3 (AD)
- Equatorial latitudes identical to August, and lower than the climatology.
- N.Hem Polar and Mid Lat values greater than previous month, S.Hem Polar and Mid Lat less than previous month.
- The S.Polar values above 30km are much less than the IG climatology
N2O (AB)
- The mean is very similar to August, where the 12km altitude (especially at the equator) is much larger than climatology at 500-700 ppbv vs 300ppbv.
- The poles are lower than before, and have a higher variability.
- There is persistent structure at 21km, S.Polar latitudes, not much stronger than last month.
- Persistent enhancements at 12km, Equ-20N.
NO2 (AD)
- S.Polar nighttime max reduced in altitude compared to previous month (30km instead of 36-42km
- Other latitudes have nighttime peak values between 33-39km
- N.Polar nighttime profile increasing, daytime profile decreasing
- No significant change at other latitudes
O3 (AD)
- N.Polar latitudes decreasing by 5-10% compared with previous month, S.Mid latitudes increasing by 5-10%, no significant change at other latitudes
- Values continue to exceed IG climatology by 1ppmv at 40km at all latitudes
- S.Hem values continue 0.5ppmv lower than climatology at 21-24km

ASSFTS-11 Workshop (8-10th Oct, Bad Wildbad, Germany) [Prev] [Next]

Some notes on presentations

Radiometric Characterisation of MIPAS/Envisat (Manfred Birk, DLR)

Estimates errors of up to 5% (for low radiances) from non-linearity correction
135Hz pointing jitter may lead to ghost spectra +/- 13cm^-1 of 1.8% amplitude - origin from Stirling cooler?
Microvibrations also lead to ghost spectra <1% amplitude.

Study of Trade-Off between accuracy and horizontal resolution (Marco Ridolfi, IFAC)

With nominal scan can retrieve 2 profiles per scan (250km spacing) with SD increased by a factor 2
With 0.1cm^-1 spectral resolution (1/4 OPD) can retrieve at 133km horizontal spacing.

Retrieval of temperature and pointing information from MIPAS limb emission specta (Thomas von Clarmann, IMK)

IMK use fixed 1km altitude grid for retrievals, which simplifies ray-tracing and FOV convolution during pT retrieval iterations
Noted 3km jump in reported tangent altitudes in early MIPAS data when new orbital parameters uploaded

MIPAS L2 Near Real Time processor performance (Piera Raspollini, IFAC)

ILS correction expected to induce a negative shift of 50-100m in pointing
Offline processor includes new convergence criteria and extended altitude range - requires approx. 2x CPU of NRT.
Tested with orbits 2994 (26Sep02) and 8225 (26Sep03)

MIPAS measurements of ClONO2 and PSCs during the Antarctic Vortex Split in September 2002 (Michael Hoepfner, IMK)

Only processed data from 18Sep02 onwards, problems with earlier data (unstable temperature retrievals)
Using Wagner & Birk (2003) ClONO2 cross-section data
CH4 and N2O sysematically higher in Sep02 than Oct02
Also retrieving ClO

Non-LTE Retrieval of NO, NO2 and CO from MIPAS-Envisat (Bernd Funke, IAA/IMK)

Jul and Sep 02 data, retrieved at 10-15km vertical resolution
Non-LTE model included as part of retrieval forward model
NO includes rotational non-LTE
NO2 only significant non-LTE effects during polar winter
Use SPIRALE CO and HALOE NO+NO2 for validation

Validation of MIPAS operational L2 products using ground-based network data (Martine de Maziere, BIRA)

Comparison with O3 measurements from Payerne show that v4.55 was worse than v4.53 (Dec02) (version history)
NO2: v4.55 and v4.57 appear to have more scatter than v4.53.

Oxford/RAL posters & presentations

REC Analysis (AD, poster)
SF6 Retrievals (AB, poster)
OPTIMO Retrievals during Split Vortex (CP, presentation)
ESA NRT CH4 & H2O Retrievals (VP, presentation)
RAL Retrievals (VJ, poster)

Oxford MIPAS meeting#41 14 Oct 03

Oxford MIPAS meeting#41
14 Oct 03