Collaborative Research: A Synthesis of Existing and New Observations of Air-Snowpack Exchanges to Assess the Arctic

积雪内部、上方和下方发生的化学和生物过程影响对流层臭氧。迄今为止的测量和简化的建模研究表明，对流层O3的影响是显着的，但现有的测量和当前的建模能力是不够的，其规模的定量估计。这是特别重要的是，以提高我们的理解积雪-大气中的O3交换，因为正在进行的和预期的未来变化，在雪，海冰和永久冻土范围所造成的气候变化，这将改变积雪O3的影响在未来。该项目提供了一种综合方法来满足这一需求，使用实地测量来填补现有知识的关键空白，并将新的和现有的数据综合到化学气候模型中。将在具有不同雪/土地类型的多个地点测量O3和NOx（NO+NO2）的空气-雪交换通量，每个地点测量一段较长的时间，以捕捉不断变化的日照的影响，积雪特性和（如适用）土壤温度和土壤氮氧化物排放。测量将包括O3和NOx水平和梯度内和以上的积雪和涡相关O3通量以上的积雪两个高度;辅助测量将表征大气湍流，光化通量，微气象参数和积雪的物理和辐射特性。实地地点包括格陵兰的Summit（代表冰川积雪）、阿拉斯加的Toolik湖（代表永久冻土上的积雪和冰冻湖泊上的积雪）和密歇根理工大学运营的白杨FACE研究基地（代表生物活性土壤上的积雪）。在科罗拉多桌山进行的仪器调试的额外测量将提供关于间歇性积雪的信息。积雪过程的新参数化将被开发并纳入全球化学-气候模式ECHAM 4和ECHAM 5-MESSy的单柱模式（SCM）版本。这些参数化的目的是描述基本的过程，并捕捉现有的和新的实地测量结果之间的变化，这些测量结果将用于模型评价。新的模型系统将被用来模拟空气-雪O3和NOx交换对北极对流层O3收支的影响，这项工作将缩小现有的差距，了解积雪过程影响O3，包括O3吸收到雪和生物活动的作用下积雪，NOx从雪中释放，和边界层O3生产造成积雪排放的O3前体。它将提供对永久冻土层上的雪和冰冻湖泊上的雪的雪-空气O3和NOx通量的第一次测量，以及对非永久冻土层上的雪的最彻底的测量。新的积雪交换模型将是对化学气候模型中积雪影响的当前模拟的一个非常重大的进步，并将使这些模型能够更好地描述北极气候变化与环境系统之间的联系。它的使用将产生积雪光化学过程对北极和亚北极对流层O3收支的影响的第一次评估，并将为评估气候变化通过改变积雪和永久冻土范围对对流层O3收支的预期影响提供基础。

Chemical and biological processes occuring within, above, and below snowpacks influence tropospheric ozone. Measurements available to date and simplified modeling studies indicate that the resulting impact on tropospheric O3 is significant, but available measurements and current modeling capabilities are insufficient for a quantitative estimate of its magnitude. It is of particular importance to improve our understanding of snowpack-atmosphere O3 exchanges because of ongoing and expected future alterations in snow, sea-ice and permafrost extent resulting from climate change, which will alter snowpack O3 impacts in the future. This project provides an integrated approach to address this need, using field measurements to fill key gaps in current knowledge and synthesizing the new and existing data into a chemistry-climate model.Air-snow exchange fluxes of O3 and NOx (NO+NO2) will be measured at multiple sites with different snow/land types, each for an extended period to capture effects of changing insolation, snowpack properties and (where applicable) soil temperature and soil NOx emissions. Measurements will include O3 and NOx levels and gradients both within and above the snowpack and eddy-correlation O3 fluxes at two heights above the snowpack; ancillary measurements will characterize atmospheric turbulence, actinic flux, micrometeorological parameters and the snowpack's physical and radiative properties. Field locations include Summit, Greenland (representing glacial snowpack), Toolik Lake, Alaska (representing snowpack above permafrost soil and snowpack over frozen lakes) and the Aspen FACE research site operated by Michigan Tech (representing snowpack above biologically active soil). Additional measurements for instrument shakedown at Table Mountain, Colorado, will provide information on intermittent snowpack.New parameterizations of snowpack processes will be developed and incorporated into single column model (SCM) versions of the global chemistry-climate models ECHAM4 and ECHAM5-MESSy. These parameterizations will be designed to describe the underlying processes and to capture variations among the available and new field measurements, which will be used for model evaluation. The new model system will be used to simulate the impact of air-snow O3 and NOx exchange upon the arctic tropospheric O3 budget.This work will close existing gaps in understanding of snowpack processes affecting O3, including O3 uptake to snow and the role of biological activity below snowpacks, NOx release from snow, and boundary layer O3 production resulting from snowpack emissions of O3 precursors. It will provide the first measurements of snow-air O3 and NOx fluxes for snow over permafrost and snow over frozen lakes, and the most thorough measurements available for snow over non-permafrost soil. The new snowpack-exchange model will be a very significant advancement over current simulations of snowpack impacts in chemistry-climate models, and will allow such models to better describe the connections between changing Arctic climate and environmental systems. Its use will produce the first assessment of the impact of snowpack photochemical processes upon the arctic and subarctic tropospheric O3 budget, and will provide the basis for assessing the expected impact that climate change will exert upon the tropospheric O3 budget through changing snowcover and permafrost extent.