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地表能量、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。鉴于蒸发过程是严重非线性的，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。据推测，与多年冻土动态、土壤湿度、植被（维管/非维管）和自由水体（湖泊）的出现相关的异质性，在使用时间和面积平均输入的情况下，导致蒸发模式估计存在很大的不确定性。本博士论文研究项目将研究北极沿海平原生态系统从景观（1平方公里）到区域（100平方公里）尺度上亚网格时空异质性对模拟蒸发估算的意义。这些影响的重要性将在适应北极生态系统的BIOME-BGC模型的框架内进行检验。BIOME-BGC是一种广泛使用的生态生理过程模型，用于计算各种尺度下的水、碳和养分通量。模型输入、校准和验证的数据将来自涡流通量塔、涡流通量飞机、野外和卫星遥感数据的组合。将在每个涡流通量塔的位置制作一幅实地高分辨率地理信息系统地图，以便在蒸发通量的模式估计中改进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认识的同时，本研究为北极生态系统的能量、碳和水循环区域模型的适应提供了基础。由于北极生态系统对温度变化的敏感性和可能放大全球变暖的潜在正反馈，因此对全球气候变化研究尤为重要。本研究试图在多个尺度上整合和综合蒸发（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式预测。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认识。最后，本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，以提高我们对北极苔原地区气候变化影响的认识。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.