Ecohydrologic Controls on Convective Rainfall Triggering and Space-Time Development

虽然夏季对流降水显着的总生长季节降雨量的贡献，它在中纬度温带地区的水文预算中最不知名的组件之一。这种不确定性源于其高时空变异性和复杂的生态生理，水文和湍流输送机制之间的相互作用在陆-气界面的敏感性。为了进一步描述对流降雨场，对流降雨和陆面强迫之间相互关系的预报和诊断措施。H1）预报：对于给定的天气条件，与土壤/植被特征有关的地表水和能量通量的综合时间历史控制着夏季对流降水的时间和开始。H2）诊断：随后的对流降水活动的时空发展，而内在的内部气象动力学在几个尺度上的作用，部分地控制了一组有限的尺度，可以从陆地表面的异质性指纹。这种“指纹”可以通过分析空间降水和少量陆地表面特征（例如，地形和土地覆盖指数）。这两个假设是通过使用大气边界层的低维动力学模型评估触发对流降雨的地表过程来解决的。对流风暴的时空结构进行了分析，土壤水分，地形，土地覆盖，在空间和小波域的互信息措施。选择北卡罗来纳州皮埃蒙特地区作为案例研究是因为该地区频繁的对流降雨模式、夏季的水文气候状况、与美国东南部大部分地区在城市和农业土地利用变化趋势方面的相似性以及其作为美国主要廷伯兰生产者的经济重要性。虽然目前的随机水文模型直接解决固有的不可预测性的降雨形成和演变，采用高度复杂的时空随机过程，存在一个“赤字”，在其物理配方。另一方面，气象学中使用的对流降水模式主要是基于基本的和机械的方法，但通常面临着许多限制，在其次网格尺度的动态重要过程的描述，如云微物理，复杂的湍流波动闭合模型，陆面过程的近似描述。所提出的方法将通过提供对流降水地面强迫的客观统计特征，并为水文模型和区域气象预测提供基准措施，弥合这一基本知识差距。拟议的工作将诊断土地利用变化对对流降水触发因素的影响及其对整个夏季降水的贡献，以评估水资源，干旱风险和廷伯兰生存能力。 该提案将培养一名研究生在水文学，气象学，生态生理学和信息理论之间的接口问题。

While summertime convective precipitation significantly contributes to the total growing season rainfall, it ranks among the least known components in the hydrologic budget of mid-latitude temperate regions. This uncertainty stems from its high space-time variability and its sensitivity to the interplay between complex eco-physiological, hydrologic, and turbulent transport mechanisms at land-atmosphere interface. To progress on the description of convective rainfall fields, both prognostic and diagnostic measures of the interrelationship between convective rainfall and land-surface forcing.H1) Prognostic: For given synoptic conditions, the integrated time history of surface water and energy fluxes, which is related to soil/vegetation characteristics, controls the timing and onset of summertime convective precipitation.H2) Diagnostic: The subsequent space-time development of convective precipitation activity, while inherently related to the internal meteorological dynamics acting at several scales, is partly controlled by a limited set of scales that can be fingerprinted from land-surface heterogeneity. This 'fingerprinting' can be statistically derived by analyzing the joint probability distributions of spatial precipitation and few land surface characteristics (e.g., topographic and land-cover indices) for different soil moisture antecedent conditions.These two hypotheses are addressed by evaluating the land-surface processes that trigger convective rainfall using low-dimensional dynamical models of the atmospheric boundary layer. The space-time structure of the convective storms is analyzed in relation to soil moisture, topography, and land cover using mutual information measures in both space and wavelet domains. The North Carolina Piedmont area is selected as a case study because of its frequent convective rainfall patterns, its summertime hydro-climatic regime, its resemblance to large parts of the Southeastern U.S. in trends of urban and agricultural land-use change, and its economic importance as the primary timberland producer in the United States.Intellectual Merit: While current stochastic hydrologic models directly address the inherent unpredictability of rainfall formation and evolution by employing highly sophisticated space-time random processes, there exists a 'deficit' in their physical formulation. On the other hand, convective precipitation models used in meteorology are primarily based on fundamental and mechanistic approaches but are routinely confronted with numerous limitations in the description of dynamically important processes at their sub-grid scale such as cloud microphysics, closure models for complex turbulent fluctuations, and approximate description of land-surface processes. The proposed approach will bridge this basic knowledge gap by offering an objective statistical characterization of the surface forcing on convective precipitation and providing benchmark measures for both hydrologic models and regional meteorological predictions.Broader impact: The proposed work will diagnose the impact of land use change on triggers of convective precipitation and its contribution to overall summertime precipitation for assessment of water resources, drought risk, and timberland viability. The proposal will train a graduate student in problems lying at the interface between hydrology, meteorology, eco-physiology, and information theory.