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

Abstract

Abstract. Column-averaged volume mixing ratios of carbon dioxide (X CO 2 ) during the period from January 2007 to May 2008 over Tsukuba, Japan, were derived using CO 2 concentrations measured by Continuous CO 2 Measuring Equipment (CME). The CMEs were installed on Japan Airlines Corporation (JAL) commercial airliners, which frequently fly to and from Narita Airport. It was assumed that CO 2 profiles over Tsukuba and Narita are the same. CO 2 profile data for 493 flights on clear-sky days were analyzed in order to calculate X CO 2 with one of two ancillary datasets: "Tsukuba observational" data (rawinsonde and meteorological tower), or "global" forecast/reanalysis and climatological data . The amplitude of the seasonal variation of X CO 2 using the ancillary data measured in Tsukuba (X CO 2 (Tsukuba observational)) was determined by a least squares fit using a harmonic function to roughly evaluate the seasonal variation over Tsukuba. The highest and lowest values of the obtained fitted curve in 2007 for X CO 2 (Tsukuba observational) were 386.4±1.0 and 381.7 ± 1.0 ppm in May and September, respectively, where the errors represent 1 standard deviation of the fit residuals. The dependence of X CO 2 on the type of ancillary dataset was evaluated. The average difference between X CO 2 from global climatological data, X CO 2 (global), and X CO 2 (Tsukuba observational), i.e., the bias of X CO 2 (global) based on X CO 2Correspondence to: M. Araki (araki@rs.kagu.tus.ac.jp) (Tsukuba observational), was found to be −0.621 ppm with a standard deviation of 0.682 ppm. The uncertainty of X CO 2 (global) based on X CO 2 (Tsukuba observational) was estimated to be 0.922 ppm. This small uncertainty relative to the GOSAT precision suggests that calculating X CO 2 using data from airliners and global climatological data can be applied to the validation of GOSAT products for X CO 2 over airports worldwide.

Validation of XCH<sub>4</sub> derived from SWIR spectra of GOSAT TANSO-FTS with aircraft measurement data

“…For these observations, we made certain assumptions. We reconstructed CH 4 profiles in the troposphere in a manner analogous to the aircraft-based XCO 2 calculations made by Araki et al (2010). First, we extrapolated the lowest aircraft data to the surface.…”

“…(2) and (3) over altitudes from the surface up to 85 km with a vertical resolution of 100 m based on the method used by Araki et al (2010) for XCO 2 . As described below (Sect.…”

Algorithm update of the GOSAT/TANSO-FTS thermal infrared CO<sub>2</sub> product (version 1) and validation of the UTLS CO<sub>2</sub> data using CONTRAIL measurements

“…We regarded the CME data obtained during the ascent and descent flights over the nine airports as part of CO 2 vertical profiles, and investigated differences between TIR and CME CO 2 data with and without applying averaging kernel functions in the altitude regions around the CME level flight observations. We assumed the CME ascending/descending CO 2 concentration at the uppermost altitude level to be constant up to the tropopause height, following the method proposed by Araki et al (2010). We used stratospheric CO 2 data taken from the Nonhydrostatic Icosahedral Atmospheric Model (NICAM)-Transport Model (TM) (Niwa et al, 2011(Niwa et al, , 2012 to create whole CO 2 vertical profiles over the airports.…”

Remotely operable compact instruments for measuring atmospheric CO<sub>2</sub> and CH<sub>4</sub> column densities at surface monitoring sites

“…Thus the CO 2 concentrations in the troposphere and the stratosphere in 2009 are estimated to be 387.1 and 377.6 ppm, respectively. Between 10 km and 20 km in altitude the concentration is assumed to be linear (Araki et al, 2010). Atmospheric CO 2 column densities measured by GOSAT (V00.20) have been officially announced and are quoted in Table 1 for 6 August and 2 September 2009.…”

“…The CO 2 concentration measured was 374.4 ± 3.6 ppm on the surface level and 388.8 ± 2.3 ppm at 10 km. The column density deduced from the concentrations is given in Table 1 where the atmospheric CO 2 concentration above 10 km was treated after the method in evaluation of CO 2 column average volume mixing ratio (VMR) over Tsukuba (Araki et al, 2010). The CO 2 concentration in the stratosphere above 20 km is considered to be five years older than that of the global mean concentration of CO 2 in the troposphere, which is 385.2 ppm in 2008 with a growth rate of 1.93 ppm/yr (WMO 2008).…”