GFIT2: an experimental algorithm for vertical profile retrieval from near-IR spectra
An algorithm for retrieval of vertical profiles from ground-based spectra in the near IR is described and tested. Known as GFIT2, the algorithm is primarily intended for CO<sub>2</sub>, and is used exclusively for CO<sub>2</sub> in this paper. Retrieval of CO<sub>2</...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-08-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/9/3513/2016/amt-9-3513-2016.pdf |
| Summary: | An algorithm for retrieval of vertical profiles from ground-based spectra in
the near IR is described and tested. Known as GFIT2, the algorithm is
primarily intended for CO<sub>2</sub>, and is used exclusively for CO<sub>2</sub> in this
paper. Retrieval of CO<sub>2</sub> vertical profiles from ground-based spectra is
theoretically possible, would be very beneficial for carbon cycle studies and
the validation of satellite measurements, and has been the focus of much
research in recent years. GFIT2 is tested by application both to synthetic
spectra and to measurements at two Total Carbon Column Observing
Network (TCCON) sites. We demonstrate that there
are approximately 3° of freedom for the CO<sub>2</sub> profile, and the
algorithm performs as expected on synthetic spectra. We show that the
accuracy of retrievals of CO<sub>2</sub> from measurements in the 1.61<i>μ</i>
(6220 cm<sup>−1</sup>) spectral band is limited by small uncertainties in calculation
of the atmospheric spectrum. We investigate several techniques to minimize
the effect of these uncertainties in calculation of the spectrum. These
techniques are somewhat effective but to date have not been demonstrated to
produce CO<sub>2</sub> profile retrievals with sufficient precision for
applications to carbon dynamics. We finish by discussing ongoing research
which may allow CO<sub>2</sub> profile retrievals with sufficient accuracy to
significantly improve the scientific value of the measurements from that
achieved with column retrievals. |
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| ISSN: | 1867-1381 1867-8548 |