ALBERT

Description: The seasonal variations in background aerosol optical depth (AOD) and aerosol type are investigated over various ecosystems in China based upon three years' worth of meteorological data and data collected by the Chinese Sun Hazemeter Network. In most parts of China, AODs are at a maximum in spring or summer and at a minimum in autumn or winter. Minimum values (0.10~0.20) of annual mean AOD at 500 nm are found in the Qinghai-Tibetan Plateau, which is located in the remote northeast corner of China, the northern forest ecosystems and Hainan Island. Annual mean AOD ranges from 0.25 to 0.30 over desert and oasis areas as well as the desertification grasslands in northern China; the annual mean AOD over the Loess Plateau is moderately high at 0.36. Regions where the highest density of agricultural and industrial activities are located and where anthropogenic sulphate aerosol and soil aerosol emissions are consistently high throughout the whole year (e.g. the central-eastern, southern and eastern coastal regions of China) experience annual mean AODs ranging from 0.50~0.80. Remarkable seasonal changes in the main types of aerosol over northern China (characterized by the Angstrom exponent, α) are seen. Due to biomass and fossil fuel burning from extensive agricultural practices in northern rural areas, concentrations of smoke and soot aerosols rise dramatically during autumn and winter (high α), while the main types of aerosol during spring and summer are dust and soil aerosols (low α). Over southeast Asia, biomass burning during the spring leads to increases in smoke and soot emissions. Over the Tibetan Plateau and Hainan Island where the atmosphere is pristine, the main types of aerosol are dust and sea salt, respectively.

Description: In recent decades much attention has been given to the Arctic environment, where climate change is happening rapidly. Black carbon (BC) has been shown to be a major component of Arctic pollution that also affects the radiative balance. In the present study, we focused on how vegetation fires that occurred in Northern Eurasia during the period of 2002–2013 influenced the budget of BC in the Arctic. For simulating the transport of fire emissions from Northern Eurasia to the Arctic, we adopted BC fire emission estimates developed independently by GFED3 (Global Fire Emissions Database) and FEI-NE (Fire Emission Inventory – Northern Eurasia). Both datasets were based on fire locations and burned areas detected by MODIS (MODerate resolution Imaging Spectroradiometer) instruments on NASA's (National Aeronautics and Space Administration) Terra and Aqua satellites. Anthropogenic sources of BC were estimated using the MACCity (Monitoring Atmospheric Composition & Climate/megaCITY – Zoom for the ENvironment) emission inventory. During the 12-year period, an average area of 250,000 km2 yr−1 was burned in Northern Eurasia and the global emissions of BC ranged between 8.0 and 9.5 Tg yr−1. For the BC emitted in the Northern Hemisphere, about 70 % originated from anthropogenic sources and the rest from biomass burning (BB). Using the FEI-NE inventory, we found that 102 ± 29 kt yr−1 BC from biomass burning was deposited on the Arctic (defined here as the area north of 67º N) during the 12 years simulated, which was twice as much as when using MACCity inventory (56 ± 8 kt yr−1). The annual mass of BC deposited in the Arctic from all sources (FEI-NE in Northern Eurasia, MACCity elsewhere) is significantly higher by about 37 % in 2009 to 181 % in 2012, compared to the BC deposited using just the MACCity emission inventory. Deposition of BC in the Arctic from BB sources in the Northern Hemisphere thus represents 68 % of the BC deposited from all BC sources (the remaining being due to anthropogenic sources). Northern Eurasian vegetation fires (FEI-NE) contributed 85 % (79–91 %) to the BC deposited over the Arctic from all BB sources in the Northern Hemisphere. Arctic total BC burden showed strong seasonal variations, with highest values during the Arctic Haze season. High winter–spring values of BC burden were caused by transport of BC mainly from anthropogenic sources in Europe, whereas the peak in summer was mainly due to the fire emissions in Northern Eurasia. BC particles emitted from fires in lower latitudes (35° N–40° N) were found to remain the longest in the atmosphere due to the high release altitudes of smoke plumes, exhibit tropospheric transport resulting in a high summer peak of burden, and grow by condensation processes. In regards to the geographic contribution on the deposition of BC, we estimated that about 46 % of the BC deposited over the Arctic from vegetation fires in Northern Eurasia originated from Siberia, 6 % from Kazakhstan, 5 % from Europe, and about 1 % from Mongolia. The remaining 42 % originated from other areas in Northern Eurasia. For spring and summer, we computed that 42 % of the BC released from Northern Eurasian vegetation fires was deposited over the Arctic (annual average: 17 %). Vegetation fires in Northern Eurasia contributed to 14 % to 57 % of BC surface concentrations at the Arctic stations (Alert, Barrow, Zeppelin, Villum, and Tiksi), with fires in Siberia contributing the largest share. However, anthropogenic sources in the Northern Hemisphere remain essential, contributing 29 % to 54 % to the surface concentrations at the Arctic monitoring stations. The rest originated from North American fires.

Description: In recent decades much attention has been given to the Arctic environment, where climate change is happening rapidly. Black carbon (BC) has been shown to be a major component of Arctic pollution that also affects the radiative balance. In the present study, we focused on how vegetation fires that occurred in northern Eurasia during the period of 2002–2013 influenced the budget of BC in the Arctic. For simulating the transport of fire emissions from northern Eurasia to the Arctic, we adopted BC fire emission estimates developed independently by GFED3 (Global Fire Emissions Database) and FEI-NE (Fire Emission Inventory – northern Eurasia). Both datasets were based on fire locations and burned areas detected by MODIS (Moderate resolution Imaging Spectroradiometer) instruments on NASA's (National Aeronautics and Space Administration) Terra and Aqua satellites. Anthropogenic sources of BC were adopted from the MACCity (Monitoring Atmospheric Composition and Climate and megacity Zoom for the Environment) emission inventory.During the 12-year period, an average area of 250 000 km2 yr−1 was burned in northern Eurasia (FEI-NE) and the global emissions of BC ranged between 8.0 and 9.5 Tg yr−1 (FEI-NE+MACCity). For the BC emitted in the Northern Hemisphere (based on FEI-NE+MACCity), about 70 % originated from anthropogenic sources and the rest from biomass burning (BB). Using the FEI-NE+MACCity inventory, we found that 102 ± 29 kt yr−1 BC was deposited in the Arctic (defined here as the area north of 67° N) during the 12 years simulated, which was twice as much as when using the MACCity inventory (56 ± 8 kt yr−1). The annual mass of BC deposited in the Arctic from all sources (FEI-NE in northern Eurasia, MACCity elsewhere) is significantly higher by about 37 % in 2009 (78 vs. 57 kt yr−1) to 181 % in 2012 (153 vs. 54 kt yr−1), compared to the BC deposited using just the MACCity emission inventory. Deposition of BC in the Arctic from BB sources in the Northern Hemisphere thus represents 68 % of the BC deposited from all BC sources (the remaining being due to anthropogenic sources). Northern Eurasian vegetation fires (FEI-NE) contributed 85 % (79–91 %) to the BC deposited over the Arctic from all BB sources in the Northern Hemisphere.We estimate that about 46 % of the BC deposited over the Arctic from vegetation fires in northern Eurasia originated from Siberia, 6 % from Kazakhstan, 5 % from Europe, and about 1 % from Mongolia. The remaining 42 % originated from other areas in northern Eurasia. About 42 % of the BC released from northern Eurasian vegetation fires was deposited over the Arctic (annual average: 17 %) during spring and summer.