Oxford MIPAS meeting#123
31 Jul 07

Present

Oxford: Harry Desmond, Anu Dudhia, Don Grainger, Jane Hurley, Gareth Thomas, Luis Millan-Valle, Joanne Walker, Claire Waymark

Instrument Status [Prev] [Next]

1st August: start a 10-day sequence based on the new 80% duty cycle (increased from 60%): 4 days NOM, 1 day MA, 3 days NOM, 2 days off.

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

L1B Data (JH) [Prev] [Next]

L1B coverage maps updated to Jul 9th

(previously reported problems with FTP transfer might have been at our end rather than at the ESA ftp site)

[L1B Data Coverage]

NOy (JW) [Prev] [Next]

Odd-nitrogen molecules retrieved from MIPAS (NOy = NO2, HNO3, N2O5)

Converting ESA L2 and Oxford L2 (>2005) data to equivalent latitude to better follow evolution through polar winter conditions
[Plot] showing air inside and outside SH vortex for days in 2002 and 2003. Can see anti-correlation between NOy and N2O in air outside vortex. This correlation breaks down inside vortex

Cloud Detection (JH) [Prev]

Comparing 4 different methods of cloud identification

Radiance Threshold (@ 961 cm^-1)
Cloud Index
SVD + Chi-Square reduction
SVD + Cloudy radiance contribution

Apply each of the above techniques to simulated data of known cloud amount

Plot "cloudiness" parameter derived from the above techniques against cloud effective fraction (=fraction of FOV filled by cloud x absorption), known from simulation inputs
Fit cubic splines to curve of cloudiness parameter v CEF
Convert scatter in results to uncertainty with which CEF could be retrieved.

Next: include effects of instrument noise on the scatter.

Polar Mesospheric Clouds (LMV) [Prev]

Averaging MIPAS L1B radiances from MA mode data between 730-950cm^-1 and 81-87km altitude and masking out any atmospheric lines

Plots show N.Hemisphere radiance for [11 Jan 2005] and [21 Jul 2005]
Higher radiances (~3nW) for polar summer (21Jul05), when PMCs expected, than polar winter (11Jan05), although winter radiances (~2nW) are not zero as might be expected - probably a radiometric offset problem.
Next: plot more days and/or separate altitudes to see if these features persist.

MIPAS/TES Retrievals (CW) [Prev] [Next]

Aim is to combine MIPAS limb measurements of stratospheric O3 with TES nadir-viewing measurements to obtain more information on tropospheric O3 profile (basically how TES was supposed to work before their problems with limb-views)

New selection of microwindows produces some improvement in results but still a bit of kink in temperature at 6km - need to check the averaging kernels for odd behaviour at this altitude

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

Running MORSE retrieval to process L1B data for selected days throughout the full and reduced resolution dataset.

pT, H2O, O3, HNO3, CH4, N2O, NO2, CFC-11, CFC-12, ClONO2, N2O5 and CO (LTE assumption).

Modifications to [Web Page] - clicking on processed days now shows zonal mean and polar plots of T and O3, as well as profile locations.
87 days processed so far

Aerosol Retrievals (GT) [Prev]

Trying to adapt the SVD approach used for cloud detection to find spectroscopic features of aerosols in MIPAS spectra.

Use the RFM to create a set of simulated spectra attempting to capture the aerosol-free variability of the atmosphere
Fit a set of singular vectors to these spectra
Large number of calculations required for variations in different molecules, so use the "Jacobian" facility of the RFM to calculate perturbed spectra simultaneously
Need to use whole MIPAS spectrum rather than upper half of A-band, but leads to problems with array sizes
Either: reduce spectral points by averaging or fit separately for each band

Cloud Index Microwindows (HD/JH) [Next]

HD is funded by the Oxford Trust/Nuffield Science Bursary Scheme.

About to start a 1-month project to see if a better pair of A-band microwindows can be found than the two currently used for cloud-detection.

ACPD Papers [Prev] [Next]

Papers selected from the ACPD website for discussion

"Short- and medium-term atmospheric effects of very large solar proton events": C.H.Jackman et al. (published 23.07.2007, open until 17.09.2007); Introduced by CW.
"Effects of total solar eclipse of 29 March 2006 on surface radiation": S. Kazadis et al. (published 29.06.2007, open until 24.08.2007); Comments being collected by LMV.
"Observed poleward expansion of the Hadley circulation since 1979": Y. Hu & Q. Fu (published 02.07.2007, open until 27.08.2007); Comments being collected by JW.
"The influence of cloud top variability from radar measurements on 3-D radiative transfer": F. Richter et al. (published 11.06.2007, open until 06.08.2007); Comments being collected by JH.

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

"Growth rates of stratospheric HCFC-22": D.P.Moore & J.J.Remedios (published 23.07.2007, open until 17.09.2007)
"MIPAS reference atmospheres and comparisons to V4.61/V4.62 MIPAS level 2 geophysical data sets": J. J. Remedios et al. (published 10.07.2007, open until 04.09.2007)
"Nitrogen compounds and ozone in the stratosphere: comparison of MIPAS satellite data with the Chemistry Climate Model ECHAM5/MESSy1": C. Brühl et al. (published 09.07.2007, open until 03.09.2007)
"Intercomparison of ILAS-II Version 1.4 and Version 2 target parameters with MIPAS-Envisat measurements": A. Griesfeller et al. (published 02.07.2007, open until 27.08.2007)
" MIPAS: an instrument for atmospheric and climate research": H. Fischer et al. (published 25.06.2007, open until 20.08.2007)

Oxford MIPAS meeting#123 31 Jul 07

Oxford MIPAS meeting#123
31 Jul 07