Methane fluxes and isotopic composition over heterogeneous landscapes of Arctic permafrost and Siberian peatlands (MICHAEL)

北极永久冻土和西伯利亚泥炭地异质景观的甲烷通量和同位素组成（MICHAEL）

• 批准号: 465048505
• 负责人: Professorin Dr. Astrid Lampert
• 金额: --
• 依托单位: Institut für Flugführung
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/465048505?language=en
• 关键词: Methane; fluxes; isotopic; composition; over

Arctic permafrost landscape and Siberian peatlands represent globally important sources of the greenhouse gas methane. Under warming climate, feedback mechanisms will further enhance methane emissions. However, only few sites with continuous measurements of methane fluxes are available in the Russian Arctic and Siberia, and they serve as reference for estimations on regional scales. Further, local small-scale heterogeneities of land cover within a landscape are understood to be one of the main sources of the uncertainty in the observed methane fluxes. A combination of several measurement methods for high spatio-temporal resolution of methane fluxes as well as of the heat and moisture budget is needed. This lack of data limits further land-cover and emission model development. Therefore, the project MICHAEL aims at i) providing high spatio-temporal resolution of methane emissions, of the turbulent heat fluxes and the isotopic composition using novel observational techniques in addition to those commonly used and ii) further develop land-surface models and parameterizations by taking into account landscape heterogeneities more adequately. Two sites are chosen for field campaigns: the Samoylov Station in the Lena River Delta and Mukhrino in the central part of West Siberia. The special focus is on small-scale variability and the impact of contrasting landscape features. During the project, continuous ground-based methane fluxes obtained using eddy-covariance and automatic chamber methods are enhanced with additional ground-based observational sites and combined with unmanned aerial system (UAS) measurements of surface and meteorological parameters, components of the surface heat balance, methane fluxes, profiles of methane concentration and methane isotopic composition. Three UAS are applied: a fixed-wing system for meteorological measurements including turbulence and radiation, a quadrocopter for obtaining vertical profiles of the methane concentration and for taking air samples that are analyzed for methane isotopic composition, and a tiltrotor system providing fluxes of methane. The UAS are operated at different locations within a radius of up to 10 km around the observatories, depending on wind direction, atmospheric stability and land surface to enable footprint calculations. Based on the results the accuracy of traditional eddy-covariance and chamber methods is evaluated and upscaling/downscaling methods are revised.Numerical simulations are used to derive the 3D variability of methane emitted into the atmosphere, using land-surface modelling to represent turbulent exchange over heterogeneous surface, and high-resolution atmospheric modelling to embed the measurements in the context of synoptic conditions. A numerical land-surface model containing also the carbon cycle is adapted to the considered landscapes. The modelling results are evaluated against observations and the impact of landscape heterogeneities is quantified.

北极永久冻土景观和西伯利亚泥炭地是全球温室气体甲烷的重要来源。在气候变暖的情况下，反馈机制将进一步增加甲烷的排放。然而，在俄罗斯北极和西伯利亚地区，只有少数几个地点可以连续测量甲烷通量，它们可以作为区域尺度估计的参考。此外，当地的小规模的土地覆盖景观内的异质性被认为是在观测到的甲烷通量的不确定性的主要来源之一。需要将几种测量方法结合起来，以获得甲烷通量以及热量和水分收支的高时空分辨率。这种数据的缺乏限制了土地覆盖和排放模型的进一步发展。因此，MICHAEL项目的目标是：一）使用除常用技术外的新观测技术，提供甲烷排放、湍流热通量和同位素组成的高时空分辨率;二）通过更充分地考虑景观异质性，进一步开发陆面模型和参数化。选择了两个地点进行实地调查：位于Lena河三角洲的Samoylov站和位于西西伯利亚中部的Mukhrino。特别关注的是小规模的变化和对比景观特征的影响。在该项目期间，通过增加地面观测点，并结合无人驾驶航空器系统对地面和气象参数、地面热平衡组成部分、甲烷通量、甲烷浓度分布和甲烷同位素组成的测量，增强了利用涡动协方差和自动箱法获得的连续地面甲烷通量。应用了三种UAS：用于气象测量（包括湍流和辐射）的固定翼系统、用于获取甲烷浓度垂直分布并采集空气样本进行甲烷同位素组成分析的四轴飞行器以及提供甲烷通量的倾转旋翼系统。无人机系统根据风向、大气稳定性和陆地表面在观测站周围半径达10公里的不同位置运行，以进行足迹计算。在此基础上，对传统的涡动相关方法和气室方法的精度进行了评价，并对升/降尺度方法进行了修正，采用数值模拟方法计算了甲烷排放的三维变率，用陆面模式模拟了非均匀地表的湍流交换，用高分辨率大气模式模拟了天气条件下的甲烷排放。一个数值陆面模型也包含碳循环适应所考虑的景观。模拟结果进行评估，对观测和景观异质性的影响进行量化。