Evaluation of MAX-DOAS aerosol retrievals by coincident observations using CRDS, lidar, and sky radiometer inTsukuba, Japan
Coincident aerosol observations of multi-axis differential optical absorption spectroscopy (MAX-DOAS), cavity ring-down spectroscopy (CRDS), lidar, and sky radiometer were conducted in Tsukuba, Japan, on 5–18 October 2010. MAX-DOAS aerosol retrieval (for aerosol extinction coefficient and aerosol op...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-07-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/8/2775/2015/amt-8-2775-2015.pdf |
| Summary: | Coincident aerosol observations of multi-axis differential optical
absorption spectroscopy (MAX-DOAS), cavity ring-down spectroscopy (CRDS),
lidar, and sky radiometer were conducted in Tsukuba, Japan, on 5–18 October
2010. MAX-DOAS aerosol retrieval (for aerosol extinction coefficient and
aerosol optical depth at 476 nm) was evaluated from the viewpoint of the
need for a correction factor for oxygen collision complexes (O<sub>4</sub> or
O<sub>2</sub>–O<sub>2</sub>) absorption. The present study strongly supports this need,
as systematic residuals at relatively high elevation angles
(20 and 30°) were evident in MAX-DOAS
profile retrievals conducted without the correction. However, adopting a
single number for the correction factor (<i>f</i><sub>O<sub>4</sub></sub> = 1.25) for all of the
elevation angles led to systematic overestimation of near-surface aerosol
extinction coefficients, as reported in the literature. To achieve agreement
with all three observations, we limited the set of elevation angles to ≤10° and adopted an elevation-angle-dependent correction
factor for practical profile retrievals with scattered light observations by
a ground-based MAX-DOAS. With these modifications, we expect to minimize the
possible effects of temperature-dependent O<sub>4</sub> absorption cross section
and uncertainty in DOAS fit on an aerosol profile retrieval, although more
efforts are encouraged to quantitatively identify a physical explanation for
the need of a correction factor. |
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| ISSN: | 1867-1381 1867-8548 |