Cape Rama is located on the west coast of India. The sampling location is on a flat rocky terrain, about 60 m above sea level. The site is devoid of vegetation over a scale of 50 m on all sides and is at least a few hundred metres away from sparse habitation. The meteorological data from Panaji show that in this part of the west coast, the wind in the afternoon (sampling time) is from the sea (onshore) all year round. In the northern summer monsoon period, this flow direction matches with the general large-scale flow and Cape Rama is located south of the inter-tropical convergence zone (ITCZ). Therefore, air samples collected during this period (June to September) represent tropical or SH oceanic air mass, representative of a wider area, and not contaminated by large industrial emission or strong ecosystem exchanges. In the northern winter monsoon period, the zonal wind direction is from the land to the sea and matches with the morning local wind (offshore). However, the same air mass is recirculated by afternoon sea breezes, with some dilution of continental trace gas signatures.