Aircraft observation of the seasonal variation in the transport of CO₂ in the upper atmosphere

Abstract

A large number of in situ carbon dioxide (CO2) measurements from 5224 flights were taken by commercial airliners from 2005 to 2010. We analyzed the seasonal cycles in tropospheric CO2 in wide areas of the world over the Eurasian continent, the North Pacific, Southeast Asia, and Oceania. In the Northern Hemisphere, large seasonal changes of CO2 in the upper troposphere are found from spring through summer at northern midlatitudes to high latitudes with significant longitudinal differences; seasonally low CO2 mixing ratios are vertically transported from the surface over the Eurasian continent and then transported eastward to the North Pacific. In the Southern Hemisphere, the CO2 in the upper troposphere increases rapidly from April to June, indicating clearly the interhemispheric transport of high CO2 from the Northern Hemisphere winter. The rapid increase in the upper southern lower latitudes is equivalent to about 0.2 Pg increase in carbon. This interhemispheric transport should be adequately represented in general circulation models for source/sink estimates by inverse methods, because it is comparable to the seasonal or net fluxes estimated for a current inversion area size or a typical subcontinental domain. Estimation for transport of CO2 through the high altitudes will be more important than ever with increasing data from aircraft observations.

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

“…This means that CO 2 concentrations in layers 9 and 10 were more affected by stratospheric air with relatively low CO 2 concentrations at the northern middle latitude in spring, when considering averaging kernels. This is consistent with the result of Sawa et al (2012) showing that the difference between upper-tropospheric and lower-stratospheric CO 2 concentrations was larger in the Northern Hemisphere in spring. Using CONTRAIL CME level flight observations that covered wide spatial areas allowed us to discuss the longitudinal differences in the characteristics of TIR UTLS CO 2 data.…”

Relative contribution of transport/surface flux to the seasonal vertical synoptic CO₂ variability in the troposphere over Narita

“…Measurements that were taken in the lower troposphere were judged to be inside the planetary boundary layer (PBL) if the altitudes of the measurements were below the height of the mixed layer estimated every 6 h. The mixed layer is defined as having a bulk Richardson number value of less than 0.25 (Troen and Mahrt, 1986). According to the method used by Sawa et al (2012), the CO 2 data in the layer with a difference of potential temperature of up to 10 K with the top of the PBL were not used in this study. The potential vorticity analysis method used by Sawa et al (2008) was applied to determine those data that were located in the stratosphere.…”

“…The observational data used in this study were derived from frequent measurements of CO 2 over Narita Airport from November 2005 to March 2009, obtained as a part of the project called Comprehensive Observation Network for TRace gases by AIrLiner (CONTRAIL) (Machida et al, 2007;Machida et al, 2008;Matsueda et al, 2008;Sawa et al, 2012). Onboard measurements of CO 2 were made by the Continuous CO 2 Measuring Equipment (CME) using a non-dispersive infrared gas analyser (NDIR).…”

Global distribution of CO<sub>2</sub> in the upper troposphere and stratosphere

“…3.2) with the observations. Figure 5a compares the time series of modelled monthly mean CO 2 with the measurements from CONTRAIL (Sawa et al, , 2012 N) and American Samoa (14 • S) delayed by 15 days. We find, consistent with Boering et al (1996) and Andrews et al (1999Andrews et al ( , 2001a, that the amplitude of the two signals is the same, and we diagnose a delay of 2 months at a higher altitude in the layer 18-19 km (not shown) in agreement with Boering et al (1996).…”