29 Mar 2021
29 Mar 2021
Improvement of Odin/SMR water vapour and temperature measurements and validation of the obtained data sets
- 1Department of Space, Earth and Environment, Chalmers University of Technology, Gothenburg, Sweden
- 2Molflow, Gråbo, Sweden
- 3Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe, Germany
- 4Instituto de Astrofísica de Andalucía, CSIC, Granada, Spain
- 5Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States
- 6Department of Physics, University of Toronto, Toronto, ON, Canada
- 1Department of Space, Earth and Environment, Chalmers University of Technology, Gothenburg, Sweden
- 2Molflow, Gråbo, Sweden
- 3Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe, Germany
- 4Instituto de Astrofísica de Andalucía, CSIC, Granada, Spain
- 5Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States
- 6Department of Physics, University of Toronto, Toronto, ON, Canada
Abstract. Its long photochemical lifetime makes H2O a good tracer for mesospheric dynamics. Temperature is also an important tracer of seasonal circulation as well as multi-year trends. In this study we present the reprocessing of 18 years of mesospheric H2O and temperature measurements from the Sub-Millimetre Radiometer (SMR) on board the Odin satellite, resulting in a part of the SMR version 3.0 level 2 data set. The previous version of the dataset showed poor accordance with measurements from other instruments, which suggested that the retrieved concentrations and temperature were subject to instrumental artifacts. Different hypotheses have been explored, and the idea of an underestimation of the single sideband leakage turned out to be the most reasonable one. The value of the lowest transmission achievable has therefore been raised to account for greater sideband leakage, and new retrievals have been performed with the new settings. The retrieved profiles extend between 40–100 km altitude and cover the whole globe to reach 85° latitudes. A validation study has been carried out, revealing an overall better accordance with the compared instruments. In particular, relative differences in H2O concentration are always in the ±20 % range between 40 and 70 km and diverge at higher altitudes, while temperature absolute differences are within ± 5 K between 40–80 km (with the exception of FM13 SMR–MLS difference reaching almost 10 K) and also diverge at higher altitudes.
Francesco Grieco et al.
Status: open (until 24 May 2021)
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RC1: 'Comment on amt-2021-53', Anonymous Referee #2, 22 Apr 2021
reply
The Grieco manuscript presents the updated retrieval of water vapor and temperature from Odin/SMR by fixing the sideband leakage issue. Validation against other satellite datasets were carried out. Improvement of data in this new version has been achieved.
The paper is well written with significant results. I recommend its pubication after a minor revision.
Major Comments:
1. page 3: line 10-line 14, References for other satellite measurements are not representative. For example, MLS, SABER, SOFIE and ACE-FTS have inappropriate citations.
2. page 5, line 7: "The a priori for water vapour instead...." More informaiton is needed. What kind of measurements at Bordeaux Observatory?
3. Figures should be descibed in sequence. For example, page 6, line 7 "Figures 12 and 13" are callled too early.
4. Structure of the paper. Many figures are put in the appendix, but are discussed in the main text. Fpr example, page 11, first paragraph. Need to rearrange.
5. page 12, line 5 "Regarding H2O, measurements are considered coincident...., while for temperature ......" the separation of time seems too long: 9 hours and 4 hours. Tides will be mixed in the comparison.
6. Contours in the appendix need improvements. Figure A5-A6, A8-19, difficult to quantify the values. Use more color table or contour interval.
7. Why SABER H2O and T are not used in the validation?
Minor comments:
1. Abstract: first line, "temperature is also important tracer" Not really. Temperature is also controlled by solar radiation and cooling. Not a dynamical tracer.
2. page 4, last line, "long wavelength"
3. page 6, line 14, what are the physics behind these r0 values? Or just empirically determined?
4. page 7, line 9 "and increased methane oxidation...."or sure about it. Any reference?
5. page 7, line 14, "geostrophic balance" please double check its accuracy.
6. page 12, line 3, "that is MIPAS", --->"such as"
Francesco Grieco et al.
Francesco Grieco et al.
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