Five-year flask measurements of long-lived trace gases in India

Abstract. With the rapid growth in population and economic development, emissions of greenhouse gases (GHGs) from the Indian subcontinent have sharply increased during recent decades. However, evaluation of regional fluxes of GHGs and characterization of their spatial and temporal variations by atmospheric inversions remain uncertain due to a sparse regional atmospheric observation network. As a result of Indo-French collaboration, three new atmospheric stations were established in India at Hanle (HLE), Pondicherry (PON) and Port Blair (PBL), with the objective of monitoring the atmospheric concentrations of GHGs and other trace gases. Here we present the results of five-year measurements (2007–2011) of CO2, CH4, N2O, SF6, CO, and H2 from regular flask sampling at these three stations. For each species, annual means, seasonal cycles and gradients between stations were calculated and related to variations in the natural GHG fluxes, anthropogenic emissions, and the monsoon circulations. Covariances between species at the synoptic scale were analyzed to investigate the dominant source(s) of emissions. The flask measurements of various trace gases at the three stations show potential to constrain the inversions of fluxes over Southern and Northeastern India. However, this network of ground stations needs further extension to other parts of India to allow a better understanding of, and constraints on the GHG budgets at regional and continental scales.