Trace gases and CO2 isotope records from Cabo de Rama, India

Concentrations of carbon dioxide (CO 2 ), methane (CH 4 ), carbon monoxide (CO), nitrous oxide (N 2 O) and hydrogen (H 2 ), and the stable carbon (δ 13 C-CO 2 ) and oxygen (δ 18 O-CO 2 ) isotopic composition of CO 2 have been measured in air samples collected from Cabo de Rama (CRI), India, for the period 1993-2002. The observations show clear signatures of Northern and Southern Hemispheric (NH and SH) air masses, mixed with their regional fluxes and chemical loss mechanisms, resulting in complex seasonal variation of these gases. The CRI measurements are compared with remote marine sites at Seychelles and Mauna Loa. Simulations of two major anthropogenic greenhouse gases (CO 2 and CH 4 ) concentrations using a chemistry-transport model for the CRI site suggest that globally optimized fluxes can produce results comparable to the observations. We discuss that CRI observations have provided critical guidance in optimizing the fluxes to constrain the regional source/ sinks balance.