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Changes in the amount and composition of tar according to superficial velocity (SV) were investigated in a downdraft biomass gasifier. SV of the downdraft gasification with air was varied in the range of 0.3-0.7 m/s, and tar was recovered at the gasifier outlet. The tar was classified as gravimetric tar and gas-chromatography-detectable (GC-detectable) tar. The lowest gravimetric tar yield (0.7%) was obtained at 0.4 m/s SV, and the highest was obtained at 0.7 m/s. GC-detectable tar yield was highest (1.5%) at 0.7 m/s. One-ring aromatics and naphthalene accounted for more than 80% of GC-detectable tar mass. Some constituents of GC-detectable tar showed specific trends according to SV, although the main composition did not show extreme change. The effect of SV on the production of gases and particles was also studied.

The snow darkening module evaluating dust, black carbon (BC), and organic carbon (OC) depositions on the mass of snow impurities and albedo has been developed for the NASA Goddard Earth Observing System, Version 5 (GEOS-5) Earth System Model, as the GOddard SnoW Impurity Module (GOSWIM). GOSWIM consists of the updated snow albedo scheme from a previous study (Yasunari et al. 2011) and a newly developed mass concentration calculation scheme, directly using aerosol depositions from the chemical transport model (GOCART) in GEOS-5. Compared to observations at Sapporo, the off-line simulations, forced by observation-based meteorology and aerosol depositions from GOES-5, reasonably simulated the seasonal migration of snow depth, albedos, and impurities of dust, BC, and OC in the snow surface. However, the simulated dust and BC mass concentrations in snow were especially underestimated except for the BC in the early winter, compared to the observations. Increasing the deposition rates of dust and BC could explain the observations. Removing BC deposition could possibly lead to an extension of snow cover duration in Sapporo of four days. Comparing the offline GOSWIM and the GEOS-5 global simulations, we found that determining better local precipitation and deposition rates of the aerosols are key factors in generating better GOSWIM snow darkening simulation in NASA GEOS-5.(Citation: Yasunari, T.

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