Oxford MIPAS meeting#137
8 Apr 08

Present

Oxford: Anu Dudhia, Jane Hurley, Luis Millan-Valle, Joanne Walker, Claire Waymark

Operating continuously since 1st Dec 2007 in standard cycle of 8 days NOM, 1 day MA, 1 day UA.

MIPAS switched off between 19:24 on 26 Mar and 10:10 on 28 Mar due to a (known) anomaly in the transfer of a command to the instrument.

Currently (7-14 Apr) observing in NOM mode

Mission Planning Document for 2008 [XLS] [HTML].
MIPAS Mission Plan v4.3 (March 08) [DOC] [PDF]
Currently defined measurement modes
Envisat Web-Site

L1B Data [Prev] [Next]

[L1B Data Coverage]

"Off-line" (OFL) L1B data available on D-PAC ftp site approximately 2 weeks after acquisition.

Recent problems in data production - no new data in past 72 hours (latest data was from 21 March, produced on 5th April)

"Near Real Time" (NRT) data available on Kiruna or ESRIN ftp sites ~ hours after acquisition.

Some irregularities in production eg duplicate orbits but different processing, and orbits/days processed out of sequence, but basically functional (eg orbits from earlier today already available).

NRT L1B Data Anomalies (AD) [Prev] [Next]

Some more anomalies noted

Reported 31Mar08: Anomalous "NUM_SWEEPS_PER_SCAN=+00028" (eg MIP_NL__1PNPDK20080329_205706_000063852067_00172_31789_4285.N1 ) - F Niro also notes same problem for orbits 31794, 31797, 31867 and reports
The investigation carried out with BOMEM has shown that:
- The L1B IPF is taking the last number of sweeps/scan found in the product in order to fill the field: NUM_SWEEPS_PER_SCAN in the SPH
- The last scan of this orbit contains 27 sweeps of nominal scene, one transitory sweep and one incomplete nominal sweep
- The L1 prototype rejects this last incomplete sweep, while the IPF takes into account this sweep, this is the cause of the problem
- BOMEM said that this discrepancy should be fixed with the new IPF 5.00
Therefore we will keep monitor this issue and we will verify this anomaly with the new IPF 5.00, expected by the end of the month
Reported 08Apr08: All the AB band spectra in file MIP_NL__1PNPDK20080407_112321_000059552067_00295_31912_0857.N1 are flagged as corrupt. F Niro responded:
Yes you are right, I checked the product, it is due to the fact that one auxiliary file (MIP_CO1) was not activated in time for the processing, an outdated file was used instead, I will see if it is possible to reprocess this orbit

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

[Oxford L2 Data Coverage]

Running MORSE to retrieve our own L2 data

Processing all new "off-line" data currently with a lag of around 3 weeks (2 weeks for L1B data to appear, 1 week to process L2 locally) - most recent day 19th March
Processing all previous Mar/Apr data (2002-2007) in parallel to provide comparison with recent data and eventually providing a complete L2 dataset - most recent day 18th March
Processing NOM mode NRT data - same L2 algorithm but restricted to pT, H2O and O3. Usually available a couple of days after acquisition. - most recent day 3rd April.

EQUAL Results (AD) [Next]

Envisat QUality Assessment with Lidar

Anne van Gijsel (RIVM, NL) has recently taken Oxford L2 MIPAS data (T,O3) from Feb08 for comparison with radiosonde and groundbased lidar and microwave measurements.

[Temperatures] generally OK 10-30km, several K too cold below 10km and several K too warm 30-40km (although lidar data is suspect).
[O3] 10s of % too high below 15km, good agreement (<5%) with sondes up to 30km, and with microwave 30-50km, but up to 20% too high compared with lidar between 35-45km, and 20-30% too low compared with microwindow 50-65km.

Next: look at more months starting from Jun 2007.

Cloud Retrievals (JH) [Prev] [Next]

Applying macroscopic parameter retrieval (Cloud top height, cloud top temperature and extinction) to simulated Cloud Spectral Database (CSDB) spectra from IMK.

Converted CSDB spectra to simulated MIPAS spectra (apply FOV convolution)
Initial retrieval attempts show a problem with how to model radiance discontinuity at cloud-top for FOV convolution if pencil beams are widely spaced (1km in CSDB).

NOy Retrievals (JW) [Prev] [Next]

Using seasonal variation in time-since-sunset at given latitudes to investigate NO2 → N2O5 conversion rate, governed by reaction rate k: NO2 + O3 → NO3 + O2

[Plot] showing reaction rate k estimated from k=½[O3]t (2([N2O5]-[N2O5]sunset)/[NO2] + 1), using observed values of NO2, N2O5 and O3, t=time since sunset
[Plot] showing above k values adjusted for standard temperature (235K) using Arrhenius relationship k=Aexp(-E/RT)

Upwards trend in winter (=longer time since sunset) in second plot may be associated with loss of NO2 to more permanent reseroir (HNO3, ClONO2)?

2007/8 Arctic Winter (AD) [Prev]

From the [Recent Trend] plots of Oxford L2 data for Dec/Jan/Feb/Mar 10mb, averaged from 65N to 90N for 2007 (black) compared to recent years:

Arctic winter now tending towards "typical" values
[Tem] plot for 0.1mb does show a response very similar to a damped harmonic oscillator following the sudden cooling at the end of January (corresponding to a warming at 10mb) - probably just coincidence.

Linear Retrievals (LMV) [Prev] [Next]

Using complete MIPAS bands but single retrieval iteration (ie no update of forward model or Jacobians) for mesospheric retrievals to improve S/N and reduce CPU cost.

Now extending linear retrieval to 18 km (lowest altitude observed in MA mode)
Comparison of zonal mean temperature for one day from [Linear Retrieval] v [MORSE] shows good qualitative agreement, although still some problems at high altitude (unlikely to be related to linearity assumption)

Temperature Tides (LMV) [Prev]

Comparison of day-night differences in equatorial MA mode temperatures shows structure with ~30km wavelength increasing with amplitude, also present in MLS data for same day.

[Plot] showing MIPAS (blue) and MLS (red) day-night differences v altitude (actually pressure)
At high altitude MLS continues oscillation as expected but MIPAS day remains warmer than night (could be non-LTE effect?)
Next: see if relative phase of MIPAS and MLS is consistent with difference in observation times (MIPAS 10.30 v MLS 13.30).

ACPD Papers [Prev] [Next]

Papers selected from the ACPD website for discussion

"Odin/OSIRIS observations of stratospheric NO3 through sunrise and sunset": C. A. McLinden and C. S. Haley (publihed 20 Mar 2008, open until 15 May 2008).; Introduced by JW.
"Comparison of cloud statistics from spaceborne lidar systems": S. Berthier et al. (publushed 12 Mar 2008, open until 07 May 2008).; Comments being collected by JH.
"Spatiotemporal variations of NOy species in the northern latitudes stratosphere measured with the balloon-borne MIPAS instrument": A. Wiegele et al. (published 05 Mar 2008, open until 30 Apr 2008).; Comments being collected by AD.
"Chemistry of sprite discharges through ion-neutral reactions": Y. Hiraki et al. (published 08 Feb 2008, discussion now closed).; Comments submitted by LMV.

Other MIPAS-related papers in the Open Discussion phase, which may be adopted at a future meeting

"Envisat MIPAS measurements of CFC-11: retrieval, validation, and climatology": L. Hoffmann et al. (published 04 Mar 2008, open until 29 Apr 2008)
"Validation and data characteristics of methane and nitrous oxide profiles observed by MIPAS and processed with Version 4.61 algorithm": S. Payan et al. (published 17 Dec 2007, open until 31 Mar 2008).

Oxford MIPAS meeting#137 8 Apr 08

Oxford MIPAS meeting#137
8 Apr 08