Past and present-day biogenic volatile organic compound emissions in East Asia

Biogenic volatile organic carbon (VOC) emissions from vegetation in East Asia are estimated for two contrasting land-cover scenarios: near present-day conditions derived from satellite data and pre-disturbed land-cover based on climatological parameters and plant functional type. Hourly fluxes of isoprene and monoterpenes are calculated on a grid of 60 km×60 km cells covering much of East Asia using meteorological conditions derived from a 12-month simulation of the region using regional climate model, monthly leaf area indexes, and the Guenther et al. (J. Geophys. Res. 101 (1995) 1345) ecosystem-dependent emission factors. Total present-day isoprene emissions are estimated at approximately 12 Tg C yr−1 and monoterpene emissions at 6 Tg C yr−1. These emissions are approximately 5.4 and 4 Tg C yr−1 lower than the estimated pre-disturbed emissions of isoprene and monoterpenes, respectively, largely due to the conversion of forested land to cropland. ORVOC emission estimates for the present-day scenario, obtained by assuming a constant ORVOC emission factor for all ecosystems, are slightly higher in magnitude than isoprene emissions. Present-day totals of combined biogenic and anthropogenic VOC emissions are generally larger than biogenic VOC emissions in the pre-disturbed scenario, indicating that human activities have led to a net increase in the atmospheric source of VOC in East Asia.