tailieunhanh - Climate Change and Variability Part 5

Tham khảo tài liệu 'climate change and variability part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 108 Climate Change and Variability The level of the monthly SO42- concentration in the beginning of the monitoring period is higher than at the end of the period but there is not a significant trend at all of the stations. For the NO3- concentration values are on the contrary higher during the winter months than during the summer months Hole et al. 2009 . The inter annual variation in the NO3-concentration is larger than in the sulphate concentration. The level of the nitrate concentration at the end of the monitoring period is lower than in the beginning at only the Pinega station. At the Janiskoski station the concentration has increased during the winter months. There are increasing trends in sulphate in precipitation at Ust-Moma in east Siberia in winter but at this station background concentrations are very low. This could be due to changes in Norilsk NE Siberia 69 21 N 88 12 E emission or variability in transport pattern Hole et al. 2006b . However Norilsk emissions are not well quantified so no clear conclusions can be drawn. SO42- concentrations measured in air at monitoring stations in the High Arctic Alert Canada and Zeppelin Svalbard and at several monitoring stations in subarctic areas of Fennoscandia and northwestern Russia show decreasing trends since the 1990s which corresponds well with Quinn et al. 2007 . At many stations there are significant downward trends for SO42- and SO2 in air both summer and winter. There are significant reductions of SO2 in Svanvik probably because emissions in the area are strongly reduced. For the air concentration of the nitrogen compounds there is no clear pattern but it is interesting to see a positive trend in summer total NO3- concentration at 3 stations. Total ammonium in air also has both positive and negative trends in summer. Historical and expected trends 2000-2030 with constant climate The DEHM model with extensive chemistry has been run with two different emissions scenarios The Business As Usual BAU and

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