Column‐averaged volume mixing ratio of CO₂ measured with ground‐based Fourier transform spectrometer at Tsukuba

Abstract

[1] We retrieved CO 2 volume mixing ratios (VMRs) from solar absorption spectra in the 1.6-mm CO 2 (30012-00001) band measured with a ground-based high-resolution Fourier transform spectrometer (FTS) at Tsukuba, Japan, using profile retrieval and scaling retrieval algorithms. We derived the time series of the column-averaged CO 2 VMRs (X CO2 ) from December 2001 to December 2007. The average difference between the X CO2 values obtained with the two algorithms was approximately 0.8 ppm. This difference was attributed to differences between the column averaging kernels of the algorithms. We corrected the distortion effect of an instrumental line shape (ILS) on X CO2 retrieval by determining information about the ILS simultaneously with X CO2 . Aircraft in situ measurements were made simultaneously with the FTS measurements over the FTS site on 10 August 2004 and 30 March 2005. The differences between the X CO2 values derived from the FTS measurements and from the aircraft in situ measurements complemented by model data were less than 1%. The diurnal variations of X CO2 derived from the FTS measurements demonstrated that X CO2 could be retrieved with a precision of $0.2%. The retrieved X CO2 values were compared with CO 2 VMRs obtained from aircraft sampling measurements up to 7 km altitude over Sagami Bay, Japan. The seasonal amplitude of the retrieved X CO2 agreed within 1 ppm with those of the CO 2 VMRs obtained from the aircraft sampling measurements above 3 km. The average seasonal amplitude of X CO2 over Tsukuba was $8 ppm. In addition, X CO2 showed an increasing trend, with a growth rate of $2 ppm/a.

CO<sub>2</sub> column-averaged volume mixing ratio derived over Tsukuba from measurements by commercial airlines

“…The values determined for a 2 (2.27 ± 0.14 and 2.45 ± 0.12 ppm/yr, where the errors are 1 standard deviation of a 2 in the fit) show tentative growth rates for X CO 2 and X CO 2 over Tsukuba during the period from January 2007 to March 2008 that are quite similar to the value of 2.2 ppm/yr for the FTS measurements by Ohyama et al (2009) Yang et al, 2007;Washenfelder et al, 2006) and the SCIAMACHY observations at north- Buchwitz et al, 2007), although the observational period of the present study is more recent.…”

“…"Clear-sky" conditions were determined by the solar absorption spectra measured by an FTS in Tsukuba (Ohyama et al, 2009). X CO 2 from the ground level to an altitude of 85 km, i.e., the entire altitudinal range, and X CO 2 for the altitudinal range of 2-10 km (hereafter X CO 2 ) were calculated and are shown in Fig.…”

“…Seasonal variation parameters of X CO 2 were obtained by a least squares fit to roughly evaluate the seasonal variation over Tsukuba. In addition, X CO 2 (Tsukuba observational) were compared with X CO 2 obtained by the groundbased FTS (Ohyama et al, 2009) during the study period.…”

EOF-based regression algorithm for the fast retrieval of atmospheric CO2 total column amount from the GOSAT observations

“…For training and validation purposes we used TCCON ground-based 2 CO X observations [20][21][22][23][24][25][26][27]. TCCON XCO 2 measurements taken within ± 1h of the GOSAT overpass time were chosen as the "known" value for the GOSAT observation if the footprint of the observation was located within a 5° latitude-longitude circle around CAI-screened data set [17].…”

Study of the footprints of short-term variation in XCO<sub>2</sub> observed by TCCON sites using NIES and FLEXPART atmospheric transport models

“…Ground-based Fourier transform spectrometer (FTS) observations available from the Total Carbon Column Observing Network (TCCON) (Deutscher et al, 2010;Geibel et al, 2010;Messerschmidt et al, 2010Messerschmidt et al, , 2012Ohyama et al, 2009;Washenfelder et al, 2006;Wunch et al, , 2015 provide dense temporal resolution and are more precise and accurate than space-based instruments. However, the number of ground-based FTS sites is limited, with just 23 operational sites and several approved for the future.…”