Doctoral Dissertation Research: Effects of Sub-Grid Spatial and Temporal Variability on Modeled Evaporation Fluxes in Arctic Coastal Plain Ecosystems

蒸发是北极冻土带生态系统表面能量、碳和水平衡之间的关键环节。由于北极生态系统对未来变化的敏感性，了解地表能量、碳和水平衡变化之间的联系对于预测气候变化对全球水、能源和碳循环的影响非常重要。考虑到蒸发过程是一个严重的非线性过程，在蒸发模型中使用时间和空间平均输入可能会导致显著的误差。假设与多年冻土动力学、土壤水分、植被(维管/非维管植物)和自由水体(湖泊)的出现有关的非均质性导致使用时间和面积平均输入的蒸发模型估计中的较大不确定性。这项博士论文研究项目将在从景观(1平方公里)到区域(100平方公里)的尺度上调查亚网格时空异质性在模拟蒸发估算中的意义。这些影响的重要性将在适应北极生态系统的BIOME-BGC模式的框架内进行审查。BIOME-BGC是一个广泛使用的生态生理过程模型，用于计算不同尺度下的水、碳和养分通量。用于模型输入、校准和验证的数据将来自涡流塔、涡流飞行器、现场和卫星遥感数据的组合。将在每个涡旋通量塔位置开发一张基于现场的高分辨率地理信息系统地图，以改进蒸发通量模型估计中的植被和土壤湿度的表示。在提高我们对北极沿海平原生态系统蒸发过程控制的理解的同时，这项研究为适应北极生态系统的能量、碳和水循环的区域模型提供了基础。北极生态系统对全球气候变化研究特别重要，因为它们对温度变化和可能放大全球变暖的潜在正反馈非常敏感。这项研究试图在多个尺度上整合和综合关于蒸发(气候系统的一个关键组成部分)的知识，以改进北极生态系统的模型预测。此外，这项研究有望增加我们对北极生态系统中大气、土壤、生物群和永久冻土之间复杂相互作用的了解。最后，这项研究的结果可以作为开发和实施完整的碳、水和氮模型的基础，以提高我们对气候变化对北极冻土带地区影响的理解。作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究生涯。

Evaporation is a key link between the surface energy, carbon and water balances of Arctic tundra ecosystems. Because of the sensitivity of Arctic ecosystems to future change, understanding the links between changes in the surface energy, carbon and water balances are important for predicting the impacts of climate change on the global water, energy and carbon cycles. Given that the evaporation process is acutely non-linear, using time and space averaged inputs in evaporation models may potentially lead to significant errors. It is hypothesized that heterogeneity associated with permafrost dynamics, soil moisture, vegetation (vascular/non-vascular) and the occurrence of free water bodies (lakes) leads to large uncertainties in model estimates of evaporation where time and area averaged inputs are used. This doctoral dissertation research project will investigate the significance of sub-grid spatial and temporal heterogeneity on modeled evaporation estimates at scales ranging from landscape (1 km2) to regions (100 km2) in Arctic Coastal Plain ecosystems. The significance of these effects will be examined within the framework of the BIOME-BGC model adapted to Arctic ecosystems. BIOME-BGC is a widely used ecophysiological process model designed to compute water, carbon and nutrient fluxes at a variety of scales. Data for model inputs, calibration, and validation will be derived from a combination of eddy flux tower, eddy flux aircraft, field, and satellite remotely sensed data. A field based, high resolution, geographic information system map will be developed at each eddy flux tower locations for improving representations of vegetation and soil moisture in model estimates of evaporative fluxes. While improving our understandings of the controls over the evaporation process in Arctic coastal plain ecosystems, this research provides the foundation for adapting a regional model of the energy, carbon, and water cycles to Arctic ecosystems. Arctic ecosystems are of particular importance to global climate change studies due to their sensitivity to temperature change and potential positive feedbacks that may amplify warming across the globe. This study seeks to integrate and synthesize knowledge of evaporation (a key component of the climate system) at multiple scales in order to improve model predictions in Arctic ecosystems. Additionally, this research is expected to increase our knowledge of the complex interactions among the atmosphere, soils, biota, and permafrost in Arctic ecosystems. Finally, results from this study may be used as a basis for developing and implementing a complete carbon, water, and nitrogen model for improving our understanding of the affects of climate change in Arctic tundra regions. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.