Carbon dioxide observations at Cape Rama, India for the period 1993-2002: implications for constraining Indian emissions

Abstract

India has the second largest population, one of fastest growing economies and is ranked third in greenhouse gas emissions by fossil-fuel burning in the world. However, there has been little monitoring of atmospheric CO₂ concentration over India to date. Here we reanalyse pioneering atmospheric CO₂ observations at Cape Rama, India (CRI) during the period from February 1993 to October 2002, using three forward transport models to simulate atmospheric CO₂ and separate tracers of terrestrial and oceanic fluxes, and fossil-fuel emissions. The CO₂ seasonal behaviour at this site has clear signals from monsoon-driven meteorology and terrestrial ecosystem activity, which are generally captured by all three models. The quality of the agreement between the simulations and the observations varies with season, with better results obtained during the southwest monsoon months when the CRI site observes the oceanic air of mostly southern hemispheric origin. Relatively poor model-data agreements in the other seasons, when air originating from the Indian subcontinent passes over the site, arise from the inability of coarse-resolution global models to represent CRI appropriately. In addition, limited atmospheric CO₂ measurements in the South Asia region only provide poor constraint on inversion fluxes. Flux signal footprint analysis of the CRI station highlights the need of extending the observation network inland and to different parts of the country for better understanding of the carbon cycle of India.