Abstract
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 an 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 the measurements of CO2, CH4, N2O, SF6, CO, and H2 from regular flask sampling at these three stations over the period 2007–2011. For each species, annual means, seasonal cycles and gradients between stations were calculated and related to variations in natural GHG fluxes, anthropogenic emissions, and monsoon circulations. Covariances between species at the synoptic scale were analyzed to investigate the likely source(s) of emissions. The flask measurements of various trace gases at the three stations have the 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 better constrain the GHG budgets at regional and continental scales.
Highlights
Since pre-industrial times, anthropogenic greenhouse gas (GHG) emissions have progressively increased the radiative forcing of the atmosphere, leading to impacts on the climate system and human society (IPCC, 2013, 2014a, b)
Non-CO2 GHG emissions are substantial in India, most of which are contributed by agricultural activities over populous rural areas (Pathak et al, 2010)
The negative gradient between Port Blair (PBL) and HLE is large during summer, possibly due to clean air masses transported from the ocean (Figs. 1a and 2b)
Summary
Since pre-industrial times, anthropogenic greenhouse gas (GHG) emissions have progressively increased the radiative forcing of the atmosphere, leading to impacts on the climate system and human society (IPCC, 2013, 2014a, b). Patra et al (2013) reported a net biospheric CO2 sink of −104 ± 150 TgC yr−1 over South Asia during 2007–2008 based on global inversions from 10 TransCom CO2 models (Peylin et al, 2013) and a regional inversion (Patra et al, 2011b), while the bottom-up approach gave an estimate of −191 ± 193 TgC yr−1 over the period of 2000–2009 (Patra et al, 2013) These estimates have uncertainties as high as 100–150 %, much larger compared to those of Europe (∼ 30 %, see Luyssaert et al, 2012) and North America (∼ 60 %, see King et al, 2015), where observational networks are denser and emission inventories are more accurate.
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