Active Layer Thickness and Moisture Content of Arctic Tundra From SVAT Models and Assimilated 1.4 or 6.9 GHz Brightness

该项目的长期目标是使近每天的卫星监测整个北极圈活动层的厚度和含水量成为可能。PIs建议在Arctic-CHAMP框架内验证两个假设：1)SVAT/Radiobrightness模式同化图尺度1.4或6.9 GHz亮度将产生可靠的多年冻土活动性层厚度和水分含量历史；2)在具有嵌入SVAT/Radiobrightness联系的分布式水文模型中同化卫星尺度1.4或6.9 GHz亮度将得到有意义的空间聚合活动层历史。这一断言得到了REBEX-3数据的支持，该数据显示，地图尺19 GHz亮度数据（~3 m）与SSM/I卫星尺度19 GHz亮度数据（~50 km）几乎相同，空间分辨率相差4个数量级。土壤-植被-大气传输（SVAT）模型描述了土壤、植被和雪中能量和水分的传输和储存过程。通过同化1.4 GHz亮度推断出的土壤顶部5 cm的水分含量，SVAT水分剖面精确到米深。虽然没有对6.9 GHz数据进行类似的测试，但这些数据对土壤湿度非常敏感，现在可以从新的AMSR卫星仪器获得。要使两种频率的同化方法在北极工作，需要开发和校准冻原SVAT模式，将活动层水分含量与微波亮度联系起来。NASA全球水和能源循环（GWEC）项目授权pi在其草原地表过程/辐射亮度（LSP/R）模型成功的基础上，开发和校准北极苔原的诊断LSP/R模型。GWEC项目包括2004年在Toolik湖附近进行的为期6周的图比例尺校准实验。pi建议(1)将校准实验扩展到整个夏季；(2)建立参数化反演模型，从校准实验中吸收1.4或6.9 GHz亮度数据，以验证假设1；(3)将冻原LSP/R模型和参数化反演模型嵌入到库帕鲁克河上游流域现有的水文模型中。(4)获取AMSR卫星6.9 GHz亮度数据，并在流域面积相当于卫星足迹（~ 2500 km2）的范围内建立1.4 GHz亮度的季节性“自然运行”数据；(5)吸收卫星和综合自然运行数据，验证假设2。这项研究是密歇根大学大气、海洋和空间科学系与电气工程和计算机科学系之间的跨学科研究。它为这些学科的科学家和工程师提供了独特的合作机会，将新技术引入北极环境科学。

The long-term objective of this project is to enable near-daily satellite monitoring of thickness and water content of the active layer throughout the circumpolar Arctic. The PIs propose to test two hypotheses within the framework of Arctic-CHAMP: 1) Assimilation of plot-scale 1.4 or 6.9 GHz brightness in SVAT/Radiobrightness models will yield reliable histories of thickness and moisture content of the permafrost active layer; and 2) Assimilation of satellite-scale 1.4 or 6.9 GHz brightness in a distributed hydrology model having embedded SVAT/Radiobrightness linkages will yield meaningful spatially aggregated active layer histories. This assertion is supported by REBEX-3 data, which show plotscale 19 GHz brightness data (~3 m) to be nearly identical to SSM/I satellite-scale 19 GHz brightness data (~50 km) - a 4 order of magnitude span in spatial resolution. Soil-Vegetation-Atmosphere Transfer (SVAT) models depict energy and moisture transport and storage processes in soil, vegetation, and snow. SVAT moisture profiles have been made accurate to meter depths through assimilation of the moisture content of the top 5 cm of soil inferred from 1.4 GHz brightness. Although similar tests have not been made with 6.9 GHz data, these data have significant sensitivity to soil moisture and are now available from the new AMSR satellite instrument. For the assimilation approach with either frequency to work in the Arctic requires that tundra SVAT models linking active layer moisture content to microwave brightness be developed and calibrated. A NASA Global Water and Energy Cycle (GWEC) Program grant is permitting the PIs to build upon the success of their prairie Land Surface Process/Radiobrightness (LSP/R) model to develop and calibrate a diagnostic LSP/R model for arctic tundra. The GWEC project includes a six-week, plot-scale calibration experiment near Toolik Lake in 2004. The PIs propose to (1) extend that calibration experiment to the entire summer season, (2) create a parameterized inversion model to assimilate 1.4 or 6.9 GHz brightness data from the calibration experiment to test hypothesis 1, (3) embed the tundra LSP/R model and the parameterized inversion model in an existing hydrology model of the upper Kuparuk River watershed, (4) acquire AMSR satellite 6.9 GHz brightness data and create a season-long "nature run" of 1.4 GHz brightness data for an area of the Watershed equal to a satellite footprint (~2,500 km2), and (5) assimilate the satellite and synthesized nature run data to test hypothesis 2. The research is interdisciplinary between the Department of Atmospheric, Oceanic, and Space Sciences and the Department of Electrical Engineering and Computer Science at the University of Michigan. It offers scientists and engineers across these disciplines unique collaborative opportunities to introduce new technologies to arctic environmental science.