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| Titel |
Ground-based integrated path coherent differential absorption lidar measurement of CO2: foothill target return |
| VerfasserIn |
S. Ishii, M. Koyama, P. Baron, H. Iwai, K. Mizutani, T. Itabe, A. Sato, K. Asai |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 6, no. 5 ; Nr. 6, no. 5 (2013-05-23), S.1359-1369 |
| Datensatznummer |
250017898
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| Publikation (Nr.) |
 copernicus.org/amt-6-1359-2013.pdf |
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| Zusammenfassung |
| The National Institute of Information and Communications Technology (NICT)
has made a great deal of effort to develop a coherent 2 μm
differential absorption and wind lidar (Co2DiaWiL) for measuring CO2 and
wind speed. First, coherent Integrated Path Differential Absorption (IPDA)
lidar experiments were conducted using the Co2DiaWiL and a foothill target
(tree and ground surface) located about 7.12 km south of NICT on 11, 27, and
28 December 2010. The detection sensitivity of a 2 μm IPDA
lidar was examined in detail using the CO2 concentration measured by the
foothill reflection. The precisions of CO2 measurements for the foothill
target and 900, 4500 and 27 000 shot pairs were 6.5, 2.8, and 1.2%,
respectively. The results indicated that a coherent IPDA lidar with a laser
operating at a high pulse repetition frequency of a few tens of KHz is
necessary for XCO2 (column-averaged dry air mixing ratio of CO2) measurement with a precision of 1–2 ppm in order to
observe temporal and spatial variations in the CO2. Statistical
comparisons indicated that, although a small amount of in situ data and the
fact that they were not co-located with the foothill target made comparison
difficult, the CO2 volume mixing ratio obtained by the Co2DiaWiL
measurements for the foothill target and atmospheric returns was about
−5 ppm lower than the 5 min running averages of the in situ sensor. Not
only actual difference of sensing volume or the natural variability of
CO2 but also the fluctuations of temperature could cause this
difference. The statistical results indicated that there were no biases
between the foothill target and atmospheric return measurements. The
2 μm coherent IPDA lidar can detect the CO2 volume mixing
ratio change of 3% in the 5 min signal integration. In order to detect
the position of the foothill target, to measure a range with a high SNR (signal-to-noise ratio), and to
reduce uncertainty due to the presence of aerosols and clouds, it is
important to make a precise range measurement with a Q-switched laser and a
range-gated receiver. |
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