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卫星能够几乎每天监测整个环极地北极活动层的厚度和水分含量。PIS建议在北极-CHAMP框架内检验两个假设：1)在SVAT/Radiobright模式中同化1.4或6.9 GHz地块尺度的亮度将产生可靠的多年冻土活动层厚度和水分历史；2)在具有嵌入SVAT/Radiobright联系的分布式水文模式中同化卫星尺度1.4或6.9 GHz亮度将产生有意义的空间聚集活动层历史。这一断言得到了REBEX-3数据的支持，REBEX-3数据显示，地块尺度的19 GHz亮度数据(~3m)与SSM/I卫星尺度的19 GHz亮度数据(~50公里)几乎相同-空间分辨率为4个数量级。土壤-植被-大气传输(SVAT)模型描述了能量和水分在土壤、植被和雪中的传输和储存过程。通过同化从1.4 GHz亮度推断的土壤表层5厘米的水分含量，使SVAT水分剖面精确到米深。虽然还没有用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卫星仪器上获得。无论哪种频率的同化方法要在北极发挥作用，都需要开发和校准将活动层水分含量与微波亮度联系起来的冻土带SVAT模型。美国宇航局全球水和能量循环(GWEC)计划赠款允许PI在其草原陆地过程/辐射亮度(LSP/R)模型的成功基础上开发和校准北极冻土带的诊断LSP/R模型。GWEC项目包括2004年在图利克湖附近进行的为期六周的地块规模校准实验。PI建议：(1)将校准实验扩展到整个夏季，(2)创建一个参数化反演模型，以同化来自校准实验1.4或6.9 GHz亮度数据以检验假设1，(3)将冻土带LSP/R模型和参数化反演模型嵌入到库帕鲁克河上游流域的现有水文模型中，(4)获取AMSR卫星6.9 GHz亮度数据，并为等于卫星足迹(~2,500平方公里)的分水岭区域创建1.4 GHz亮度数据的一整季“自然运行”，和(5)同化卫星和合成的自然运行数据来验证假设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交叉学科。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.