简体中文


Summary
Highlights

We present an updated carbon flux estimate for Asia by introducing aircraft CO2 measurements from the CONTRAIL (Comprehensive Observation Network for Trace gases by Airline) program into an inversion modeling system based on the CarbonTracker framework over the period 2006-2010.

Our work complements previous inverse modeling studies as it:

  1. Presents the inverted CO2 results of Asian weekly net ecosystem exchange not shown previously;
  2. Uses surface observations not available in an earlier top-down exercise;
  3. Assimilates the continuous CO2 observation from a number of Asian continental sites for the first time;
  4. Includes extra free tropospheric CO2 observations to further constrain the estimate;
  5. Use a two-way atmospheric transport model with higher horizontal resolution than previous global CO2 data assimilation studies that zoomed in Asia (see Figure 1).

Figure 1: TM5 global grid (3x2) with zoom over Asia (1x1)

Estimates of CO2 sources and sinks

We estimated the averaged annual total Asian terrestrial land CO2 sink was about -1.56 Pg C yr-1 over the period 2006-2010, which offsets about three quarters of the fossil fuel emission from Asia (+4.15 Pg C yr-1). The uncertainty of the terrestrial uptake estimate was derived from a set of sensitivity tests and ranged from -1.07 to -1.80 Pg C yr-1, comparable to the formal Gaussian error of ±1.18 Pg C yr-1 (1-sigma). The largest sink was found in forests, predominantly in coniferous forests (-0.64 Pg C yr-1) and mixed forests (-0.14 Pg C yr-1); and the second and third large carbon sinks were found in grass/shrub lands and crop lands, accounting for -0.44 Pg C yr-1 and -0.20 Pg C yr-1, respectively.

Atmospheric CO2 observations

Two sets of atmospheric CO2 observation data over Asia were assimilated:

  • Surface CO2 observations distributed by NOAA-ESRL and by the WDCGG(World Data Centre for Greenhouse Gases) for the period 2006-2010 (see Figure 2a). Individual time series in this surface set were provided by many individual PIs which we kindly acknowledge;
  • For the free tropospheric CO2 observation, we use the aircraft measurements derived from the CONTRAIL project for the period 2006-2010 (see Figure 2b).

We use free tropospheric continuous aircraft measurements from the CONTRAIL program to constrain the inverted CO2 flux. Note that stratospheric CONTRAIL CO2 data were not included into the CTDAS for the stratospheric observation had a seasonal phase shifting and its smaller amplitude was hard to comparable to the tropospheric data. A summary of the CONTRAIL aircraft measurements is presented in Figure 2b. The CONTRAIL aircraft data are reported on the NIES 09 CO2 scale, which are lower than the WMO−X2007 CO2 scale by 0.07 ppm at around 360 ppm and consistent in the range between 380 and 400 ppm. Thus the CONTRAIL CO2 data sets are comparable to surface data well. We follow the method from Niwa, et al. (2012) to divide the data into 4 vertical bins (575−625, 465−525, 375−425, 225−275 hPa) from ascending & descending profiles and one vertical bin (225−275 hPa) from leveling cruise. We also divide CONTRAIL data into 42 horizontal bins/regions (Figure 2b), which amounts to a total of 65 bins corresponding to horizontal and vertical bins/regions. Before daily averaging the CONTRAIL measurements for each 65 regional/vertical bins,we pre-process the aircraft data to obtain free troposphere CO2 values by filtering out of the stratospheric CO2 data using the threshold of potential vorticity (PV) > 2 PVU (1 PVU= 10-6 m2 s-1 K kg-1), in which PV is calculated from the TM5 (ECMWF temperature, pressure and wind fields ). A total number of 10,467 CO2 aircraft observations over Asia, which retrieved from the ascending, descending vertical profiles and the leveling cruise over the airports below 625hPa during January 2006 to December 2010, have been used in our inversion.



Figure 2. (a) Map of the Asian surface observation sites, along with the map of the ecoregion types from Olson, et al. (1985) with 19 land cover classes as used in this study. A map of the global surface observation sites from the NOAA-ESRL, CSIRO and WDCGG network are in the Figure 2a; (b) Asian CONTRAIL CO2 observations map, along with 42 horizontal regions. The red rectangles represent the 9 regions covering the ascending and descending data (included 4 vertical bins at 575-625, 475-525, 375-425, 225-275 hPa) over airports, and the blue rectangles indicate the other 33 regions covering the cruise data (included 1 bin at 225-275 hPa).

CarbonTracker Europe is a Wageningen University contribution
to the Integrated Carbon Observing System (ICOS)




京公网安备 11010502044510号