瓦里关温室气体本底研究的主要进展

PROGRESS IN THE STUDY OF BACKGROUND GREENHOUSE GASES AT WALIGUAN OBSERVATORY

由于温室气体浓度显著增长及其在气候与环境变化中的作用,国际上众多的科学计划和观测体系都把它们的时空分布、源汇及趋势列为重要内容,获得的各种资料在评价人类活动对气候和环境的影响及有关对策研究中起着关键作用。文章阐述了在中国内陆本底地区开展温室气体长期、定点观测的意义和必要性,系统地讨论了10多年来中国瓦里关本底站温室气体本底研究的主要进展。利用瓦里关经严格国际比对和质量控制的大气CO2、CH4长期观测资料,结合同期的地面风资料进行统计分析,建立了瓦里关大气CO2和CH4本底资料筛选方法;利用本底观测资料,研究了瓦里关大气CO2及其δ13C、CH4和CO本底变化及源汇特征所体现的亚洲内陆地域特点和全球代表性,并进一步与同期、同纬度海洋边界层参比值(MBL)以及北半球其他6个大气本底站同期观测数据对比分析,发现了瓦里关大气CH4和CO独特的季节变化并探讨了成因;根据空气团后向轨迹簇所途经的下垫面源汇同观测的大气CO2和CH4浓度变化之间的关系,探讨了瓦里关大气CO2和CH4的输送来源;利用Hysplit-4扩散与输送模式,计算了冬、夏典型月份人为源和自然生态系统源汇对瓦里关大气CO2浓度变化的贡献。并在现有基础上,提出了有待进一步解决的科学问题。

As greenhouse gas concentrations rise well above their natural levels, resulting in catastrophic impact on the climate and environment, their temporal and spatial distributions as well as source and sink characteristics have been incorporated into most international science plans and integrated observational systems. Measurements of background greenhouse gases are made globally and it is the experimental basis to evaluate their anthropogenic impact and to study the relative mitigating decisions. There remain, however, large uncertainties in the derived source/sink values, partly due to a shortage of observational data. This paper summarizes a decadal progress in the study of background greenhouse gases at Waliguan Observatory （WLG） in western China, and brings forward an indispensable requirement to carry out long-term systematic observations that represent typical background regions of China. By using the quality controlled in-situ measurements, background data selection procedures for the atmospheric CO2 and CH4 at WLG are developed based on local horizontal and vertical winds. On the basis of observation, background variations and source/sink characteristics of atmospheric CO2, CH4 and CO at WLG are investigated that demonstrate both the Asian inland and global representatives. In addition, the atmospheric CO2, CH4 and CO data at WLG are compared to the data from 6 selected Northern Hemispheric （NH） sites in the NOAA ESRL air sampling network as well as to the Marine Boundary Layer （MBL） reference value from 1992 to 2004 to better address their common and specific features. Unique seasonal cycles of the atmospheric CH4 and CO at WLG are revealed and possible drivers discussed. The atmospheric CO2 and CH4 source/sink identification at WLG are performed by the isobaric back trajectory clusters. By means of the Hysplit-4 transport/diffusion model, the CO2 variation at WLG in January and July 1999 are simulated and compared with observations. Based on a series of uncertainties at present, this paper at last puts forward a number of scientific issues remaining to be resolved.