科研之友
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摘要
In this study, observed episodes of CO2 concentrations at eight Northern Hemisphere (NH) sites from 1993 to 2012 were analyzed. Five-day back trajectories were calculated for a potential source contribution PSCF) analysis. A normalized weight factor related to the occurrence of the episodes was applied to derive more reasonable CO2 elevations and sequestrations. Weighted elevated (Delta CO2(W_E)) and sequestered (Delta CO2(W_S)) CO2 episodes had large spatial discrepancies due to the differentiation of strength and patterns of CO2 emissions/sinks in different regions. The most significant enhancement in CO2 episodes was observed at Asian sites: Delta CO2(W_E) increased by approximately 56% at an annual rate of similar to 4% yr(-1) from 1995 to 2010 at Waliguan (WLG) and by approximately 39% (similar to 3% yr(-1)) from 1997 to 2012 at Yonagunijima (YON). According to the PSCF analysis, these increases are largely attributed to the rapid increase in emissions in China. However, Delta CO2(W_S) was also enhanced by 34.4% with a growth rate of 23% yr(-1) at WLG from 1995 to 2010 and similar to 26.2% (1.7% yr(-1)) at YON from 1997 to 2012. Both CO2(W_E) and Delta CO2(W_S) showed decreasing or relatively flat trends at Monte Cimone and Schauinsland, indicating reductions in emissions and sinks in central Europe. The different intensities/trends in emissions and sinks observed at different sites in the NH show that estimating future CO2 levels is a complex problem. Atmospheric inverse and process-based ecosystem models should use more regional input data at high temporal and spatial resolutions for future carbon flux estimations.
