Retrieval and validation of MetOp/IASI methane
A new IASI methane product developed at the Royal Belgian Institute for Space Aeronomy (BIRA-IASB) is presented. The retrievals are performed with the ASIMUT-ALVL software based on the optimal estimation method (OEM). This paper gives an overview of the forward model and retrieval concept. The u...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-12-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/10/4623/2017/amt-10-4623-2017.pdf |
| Summary: | A new IASI methane product developed at the Royal Belgian
Institute for Space Aeronomy (BIRA-IASB) is presented. The retrievals are
performed with the ASIMUT-ALVL software based on the optimal estimation
method (OEM). This paper gives an overview of the forward model and retrieval
concept. The usefulness of reconstructed principal component compressed (PCC)
radiances is highlighted. The information content study carried out in this
paper shows that most IASI pixels contain between 0.9 and 1.6 independent
pieces of information about the vertical distribution of CH<sub>4</sub>, with a
good sensitivity in the mid- to upper troposphere. A detailed error analysis
was performed. The total uncertainty is estimated to be 3.73 % for a
CH<sub>4</sub> partial column between 4 and 17 km. An extended validation with
ground-based CH<sub>4</sub> observations at 10 locations was carried out. IASI
CH<sub>4</sub> partial columns are found to correlate well with the ground-based
data for 6 out of the 10 Fourier transform infrared (FTIR) stations with
correlation coefficients between 0.60 and 0.84. Relative mean differences
between IASI and FTIR CH<sub>4</sub> range between −2.31 and 4.04 % and are
within the systematic uncertainty. For 6 out of the 10 stations the relative
mean differences are smaller than ±1 %. The standard deviation of the
difference lies between 1.76 and 2.97 % for all the stations. |
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| ISSN: | 1867-1381 1867-8548 |