Key steps in atmospheric evolution occurred in the Archaean.The Hadean atmosphere was created by the inorganic processes of volatile accretion from space and degassing from the interior,and then modified by chemical a...Key steps in atmospheric evolution occurred in the Archaean.The Hadean atmosphere was created by the inorganic processes of volatile accretion from space and degassing from the interior,and then modified by chemical and photochemical processes.The air was probably initially anoxic,though there may have been a supply of oxidation power as a consequence of hydrodynamic escape to space of hydrogen from water.Early subduction may have removed CO2 and the Hadean planet may have been icy.In the Archaean,as anoxygenic and then oxygenic photosynthesis evolved,biological activity remade the atmosphere.Sedimentological evidence implies there were liquid oceans despite the faint young Sun.These oceans may have been sustained by the greenhouse warming effect of biologically-made methane.Oxygenesis in the late Archaean would have released free O2 into the water.This would have created oxic surface waters,challenging the methane greenhouse.After the Great Oxidation Event around 2.3 to 2.4 billion years ago,the atmosphere itself became oxic,perhaps triggering a glacial crisis by cutting methane-caused greenhouse warming.By the early Proterozoic,all the key biochemical processes that maintain the modern atmosphere were probably present in the microbial community.展开更多
An advanced carbon dioxide retrieval algo- rithm for satellite observations has been developed at the Institute of Atmospheric Physics, Chinese Academy of Sciences. The algorithm is tested using Greenhouse gases Obser...An advanced carbon dioxide retrieval algo- rithm for satellite observations has been developed at the Institute of Atmospheric Physics, Chinese Academy of Sciences. The algorithm is tested using Greenhouse gases Observing SATellite （GOSAT） LIB data and validated using the Total Column Carbon Observing Network （TCCON） measurements. The retrieved XCO2 agrees well with TCCON measurements in a low bias of 0.15 ppmv and RMSE of 1.48 ppmv, and captured the seasonal vari- ation and increasing of XCO2 in Northern and Southern Hemisphere, respectively, as other measurements.展开更多
In this study, we explore the feasibility of optimizing ecosystem photosynthetic and respiratory parameters from the seasonal variation of the net carbon flux. An optimization scheme is proposed to estimate two key pa...In this study, we explore the feasibility of optimizing ecosystem photosynthetic and respiratory parameters from the seasonal variation of the net carbon flux. An optimization scheme is proposed to estimate two key parameters （V2max and Q10） by exploiting the seasonal variation in the net ecosystem carbon flux retrieved by an atmospheric inversion system. This scheme is implemented to estimate V25max and Q10 of the boreal ecosystem productivity simulator （BEPS） to improve its NEP simulation in the boreal North American region. Then, in situ NEE observations at six eddy covariance sites are used to evaluate the NEE simulations from BEPS with initial and optimized parameters. The results show that the performance of the optimized BEPS is superior to that of the BEPS with the default parameter values. These results implicate that it is possible to optimize ecosystem model parameters by different sensitivities of V25max and Q10 during growing and non-growing seasons through atmospheric inversion or data assimilation techniques.展开更多
文摘Key steps in atmospheric evolution occurred in the Archaean.The Hadean atmosphere was created by the inorganic processes of volatile accretion from space and degassing from the interior,and then modified by chemical and photochemical processes.The air was probably initially anoxic,though there may have been a supply of oxidation power as a consequence of hydrodynamic escape to space of hydrogen from water.Early subduction may have removed CO2 and the Hadean planet may have been icy.In the Archaean,as anoxygenic and then oxygenic photosynthesis evolved,biological activity remade the atmosphere.Sedimentological evidence implies there were liquid oceans despite the faint young Sun.These oceans may have been sustained by the greenhouse warming effect of biologically-made methane.Oxygenesis in the late Archaean would have released free O2 into the water.This would have created oxic surface waters,challenging the methane greenhouse.After the Great Oxidation Event around 2.3 to 2.4 billion years ago,the atmosphere itself became oxic,perhaps triggering a glacial crisis by cutting methane-caused greenhouse warming.By the early Proterozoic,all the key biochemical processes that maintain the modern atmosphere were probably present in the microbial community.
基金supported by the Strategic Priority Research Program-Climate Change:Carbon Budget and Relevant Issues(XDA05040200)the National High-tech Research and Development Program(2011AA12A104)
文摘An advanced carbon dioxide retrieval algo- rithm for satellite observations has been developed at the Institute of Atmospheric Physics, Chinese Academy of Sciences. The algorithm is tested using Greenhouse gases Observing SATellite （GOSAT） LIB data and validated using the Total Column Carbon Observing Network （TCCON） measurements. The retrieved XCO2 agrees well with TCCON measurements in a low bias of 0.15 ppmv and RMSE of 1.48 ppmv, and captured the seasonal vari- ation and increasing of XCO2 in Northern and Southern Hemisphere, respectively, as other measurements.
基金supported by the National Basic Research Program of China(2010CB950703)the National Natural Science Foundation of China(41571338)
文摘In this study, we explore the feasibility of optimizing ecosystem photosynthetic and respiratory parameters from the seasonal variation of the net carbon flux. An optimization scheme is proposed to estimate two key parameters （V2max and Q10） by exploiting the seasonal variation in the net ecosystem carbon flux retrieved by an atmospheric inversion system. This scheme is implemented to estimate V25max and Q10 of the boreal ecosystem productivity simulator （BEPS） to improve its NEP simulation in the boreal North American region. Then, in situ NEE observations at six eddy covariance sites are used to evaluate the NEE simulations from BEPS with initial and optimized parameters. The results show that the performance of the optimized BEPS is superior to that of the BEPS with the default parameter values. These results implicate that it is possible to optimize ecosystem model parameters by different sensitivities of V25max and Q10 during growing and non-growing seasons through atmospheric inversion or data assimilation techniques.
