Updated global volcanic sulfur emissions and the direct radiative forcing during 2005-2012: GEOS-Chem simulations with constraints from OMI and CALIOP
Tuesday, 16 December 2014
An 8-year volcanic emission inventory for 2005-2012 is obtained based upon SO2 product from OMI (The Ozone Monitoring Instrument) and ancillary information from ground-based reports. It includes contributions not only from global eruptive volcanoes but also 8 near-equator degassing volcanoes. Emissions from Nyamuragira in November 2006 November and Grimsvotn in May 2011 that were missed in the IPCC-5 inventory are now included. Overall, in comparison with our new inventory, well-used AEROCOM eruptive volcanic emission has high biases by a factor of 4. With updated volcanic emission inventory, the volcanic sulfate distribution was simulated from global transport model GEOS-Chem, which shows consistent temporal evolution of zonally averaged sulfate AOD with the CALIOP AOD above 10 Km, and the modeled AOD capture every eruption volcano sulfate with similar magnitude as CALIOP counterpart. The 8 years average contribution from eruptive SO42- to total SO42- loading is ~10% over the most area, and is only significant for those eruptions above 10 km, with the maximum ratio of 30% along tropical area. Tropical degassing volcano SO42- barely reaches above 10 km, but is regionally dominate type of aerosols (60%+ in terms of mass in lower atmosphere) over Hawaii, and ocean area at northeast to Australia. The 8 years averaged global eruption volcano sulfate forcing (-0.09 Wm-2) is found to be slightly higher than reported by IPCC, and the tropical degassing sulfate forcing is estimated as -0.02 Wm-2. The global and monthly mean sulfate forcing efficiency to SO2 emission was calculated for 3 categories. For eruptive volcanoes sulfate the forcing efficiency is more than 5 times of the counterpart of the background (mostly anthropogenic) sulfate, and for the 8 tropical degassing volcanoes sulfate it is slight higher than the one for background sulfate. That indicates the injection height is an important factor to decide the volcano sulfate forcing efficiency. The updated volcanic database is available upon request.