A Numerical Study of the Relationship between the Carbon Cycle and the Land Surface Processes in the Northern Hemisphere Related to Recent El Ni?o Events

摘要

This study investigates the natural relationships between the carbon cycle andlandsurface processes in the Northern Hemisphere, relatedto recent El Ni?o events by a general circulation model with a Biosphere?Atmosphere Interaction Model Version 2 (BAIM2). Two cases are simulated; the periods of Case 1 and Case 2 are from 1996 to 2000 and from 2001 to 2005, respectively. Case 1 includedthe El Ni?o event from 1997 to 1998, andCase 2 includedthat from 2002 to 2003 in each simulation period. The physical and biological mechanisms of the relationship between the changes of landsurface processes with climate changes andvariations of CO_2 exchange between the atmosphere andterrestrial ecosystem are systematically examinedusing the results of direct simulation with a terrestrial biosphere-atmosphere fully coupledglobal climate model. In 1998 and2003, high surface temperature andlow soil wetness in the Eurasian Continent andNorth America occurredin the warm season in the Northern Hemisphere. These climate conditions are thought to have induced relatively low gross primary production and net ecosystem production values and contributed to anomalously high atmospheric CO_2 concentrations in these years. The results of this study suggest that there is a common feature in the relationship between the carbon cycle andlandsurface processes in the Northern Hemisphere, relatedto recent El Ni?o events. Specifically, an anomaly of the atmospheric circulation in the warm season in the Northern Hemisphere in the year El Ni?o event ends, which is most likely induced by the global teleconnection associatedwith the tropical sea surface temperature anomaly, causes an anomaly in the landsurface processes; this in turn induces anomalously low carbon absorption by the terrestrial ecosystem, which affects the variation of atmospheric CO_2 concentration growth rate.