Open AccessPartial CO2 Column-Averaged Dry-Air Mixing Ratio from Measurements by Coherent 2-μm Differential Absorption and Wind Lidar with Laser Frequency Offset Locking
Author(s) -
Shoken Ishii,
K. Mizutani,
Philippe Baron,
Hironori Iwai,
Ryoko Oda,
Toshikazu Itabe,
Hirotake Fukuoka,
Takayoshi Ishikawa,
M. Koyama,
Tomoaki Tanaka,
Isamu Morino,
Osamu Uchino,
Atsushi Sato,
Keisuke Asai
Publication year - 2012
Publication title -
journal of atmospheric and oceanic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.774
H-Index - 124
eISSN - 1520-0426
pISSN - 0739-0572
DOI - 10.1175/jtech-d-11-00180.1
Subject(s) - lidar , laser , environmental science , mixing ratio , cirrus , remote sensing , optics , materials science , atmospheric sciences , physics , geology
A coherent 2-μm differential absorption and wind lidar (Co2DiaWiL) with a 2-μm single-frequency Q-switched laser with laser frequency offset locking was used for long-range CO2 measurement. The frequency stabilization of the single-frequency λ on pulsed laser was 1.0 MHz. Experimental horizontal CO2 measurement over a column range of 2.6–5.6 km and 900 shot pairs (1-min integration time) was conducted on 22 October 2009 to examine the detection sensitivity of the Co2DiaWiL. The achieved precision was less than 2.1%. The root-mean-square of the differences between the 30-min CO2 averages measured by the Co2DiaWiL and a ground-based in situ instrument was 0.9% (3.5 ppm). Experimental vertical CO2 measurements were conducted in February 2010 and January and February 2011. The partial CO2 column-averaged dry-air mixing ratios (XCO2) for an altitude between 0.4 and 1.0 km in 2010 and 2011 were 403.2 ± 4.2 and 405.6 ± 3.4 ppm, respectively. In the paper, the Co2DiaWiL results were well validated carefully against those of the airborne in situ instrument; they agreed well within the margin of error. The values of XCO2 measured in presence of cirrus clouds near the tropopause (hard target cases) show a difference of less than 4.1 ppm with the airborne measurements performed on 14 February 2010. This result demonstrates the capability of the Co2DiaWiL to measure XCO2 within a precision better than 1%.