Collaborative Research: Understanding the Role of Landcover and Landform in the Spatial Organization of Orographic Clouds and Rainfall

合作研究：了解土地覆盖和地貌在地形云和降雨空间组织中的作用

• 批准号: 0711414
• 负责人: Miles Silman
• 金额: $ 12.73万
• 依托单位: Wake Forest University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0711414&HistoricalAwards=false
• 关键词: Collaborative; Research; Understanding; Role; Landcover

Mountains supply freshwater for over 60% of the world's population making the location and timing of orographic precipitation crucial in determining the availability and utility of water resources and ecosystem services. Montane systems also harbor Earth's most important biodiversity hotspots, and species and ecosystem responses to climate variability and change in these regions are critically dependent on cloud and precipitation regime. The objective of this proposal is to investigate whether and how landform and landcover modulate the spatial and temporal variability of orographic clouds and precipitation in tropical high mountains, a high priority area for biodiversity conservation and human water supply. The central research hypothesis is that evapotranspiration is a critical source of moisture to the atmospheric boundary layer (ABL) either locally and, or remotely via moist transport by diurnal mountain-valley circulations, lowering the cloud base at high elevations during the afternoon, and enhancing thermodynamic instability at locations in the landscape where precipitable water and CAPE (Convective Available Potential Energy) attain collocated night-time maxima. Spatial patterns in the organization of clouds and precipitation should therefore be explained by the spatial variability of vegetation and soil moisture patterns on altitudinal gradients, and by how this translates into the spatial variability of the diurnal cycle of latent heating fluxes between the land surface and the lower troposphere. To evaluate this hypothesis, the research will focus on a tropical montane cloud forest in the Central Andes in Peru, leveraging on ongoing multidisciplinary, multi-institutional ecological research by the Andes Biodiversity and Ecosystem Research Group (ABERG) that includes the University of Edinburgh and Oxford University in the UK, and FIT, Wake Forest and Duke Universities among others in the US.ABERG has installed a large array of vegetation plots and associated ecosystem function measurements centered on the Kosnipata Valley, extending from the high Andes into the Amazonian lowlands. The plot network is anchored by a series of 21 mapped, measured, and vouchered 1 ha tree plots comprising ~15,000 stems. These plots are embedded in an array of existing weather stations and data loggers ranging from 3450m to 250m. The hectare plots also form the basis of an intensive ecosystem function experiment, with plots along the main transect having dendrometers on 20% of the trees chosen in a stratified random sample. Subsets of plots are also studied for leaf, fruit, and fine root productivity, forest structure and leaf area index, and are instrumented to log soil moisture, understory and canopy light levels, rainfall, winds velocity and direction. Carbon-cycle measurements on photosynthesis, leaf, stem, and soil respiration are also taken at these plots. An intensive hydrological study plot at 3000m is also instrumented for throughfall, stemflow, and cloud interception measurements. The investigation relies on diagnostic process studies integrating satellite products and surface observations from existing and augmented networks to survey the space-time relationships between hydro-eco-geomorphologic regimes and cloudiness. High-resolution simulations (1km or less) using a coupled land-atmosphere, non-hydrostatic, cloud-resolving model will be used to investigate the physical linkages among the spatial patterns of topography, vegetation, soil moisture and the diurnal cycle of monsoon rainfall in the central Andes at the valley-ridge scale. Specifically, the following science questions will be addressed: (1) What is the contribution of evapotranspiration to the diurnal cycle of the energy budget of the lower troposphere in tropical mountainous regions? How does it vary spatially with elevation and landform (ridges versus valleys, windward versus leeward slopes, foothills versus high peaks)? (2) How does transversal (lateral) mountain variability in the spatial arrangement of landform and vegetation affect the diurnal cycle of convective activity and precipitation during the monsoon? (3) What is the relationship between the observed multi-scaling behavior of cloud fields from satellite imagery and the dominant spatial scales of convective activity associated with topography and, or land-use/land-cover patterns? (4) How can the current trends of land-use/land-cover change, and in particular deforestation and extension of agricultural activity to the highlands, change the water cycle in tropical mountainous regions? What are the consequences of these changes for the long-term sustainability of tropical mountain ecosystems and water resources? Though in the tropics, the outcomes of this work are relevant for mid-latitude mountainous regions, especially the western US where orographic precipitation (rain and snowfall) is the dominant freshwater resource. Finally, the study area is undergoing strong land-use change from anthropogenic eradication of the natural tree line, and from the construction of the inter-oceanic highway. The research findings should lead to an improved science basis for sustainable environmental planning and adaptation to climate climate variability and change in mountainous regions.

山区为世界上60%以上的人口提供淡水，这使得地形降水的位置和时间对于确定水资源和生态系统服务的可用性和效用至关重要。 山地系统也是地球上最重要的生物多样性热点，这些地区的物种和生态系统对气候变异和变化的反应严重依赖于云和降水状况。 该提案的目的是调查地形和土地覆盖是否以及如何调节热带高山（生物多样性保护和人类供水的高度优先区域）地形云和降水的空间和时间变异性。 核心研究假设是蒸散是大气边界层（ABL）的关键水分来源，无论是本地还是远程，通过昼夜山谷环流的潮湿输送，在下午降低高海拔地区的云底，并在可降水和CAPE的景观位置增强热力学不稳定性（对流可用势能）达到并置的夜间最大值。 因此，云和降水组织的空间格局应解释为植被和土壤水分格局在海拔梯度上的空间变异性，以及如何将其转化为陆面和对流层低层之间潜热通量日循环的空间变异性。 为了评估这一假设，研究将集中在秘鲁中部安第斯山脉的热带山地云雾林，利用安第斯山脉生物多样性和生态系统研究小组（ABERG）正在进行的多学科，多机构生态研究，其中包括英国爱丁堡大学和牛津大学，以及FIT，美国的维克森林大学和杜克大学等。ABERG以科斯尼帕塔山谷为中心安装了大量植被地块和相关的生态系统功能测量，从安第斯山脉延伸到亚马逊低地。 小区网络由一系列21个映射，测量和vouchered 1公顷树小区，包括约15，000个茎锚定。这些地块嵌入在一系列现有的气象站和数据记录仪中，范围从3450米到250米。公顷地块也形成了一个密集的生态系统功能实验的基础上，与地块沿着主要样带有树木计在分层随机抽样选择的树木的20%。 还研究了叶，果实，细根生产力，森林结构和叶面积指数的地块的子集，并仪器记录土壤水分，林下和冠层光照水平，降雨量，风速和方向。 还在这些地块上对光合作用、叶、茎和土壤呼吸进行了碳循环测量。 在3000米的密集的水文研究地块也仪表穿透雨，茎流和云拦截测量。调查依赖于诊断过程的研究整合卫星产品和现有的和增强的网络调查水文生态地貌制度和云量之间的时空关系的表面观测。 将使用一个陆地-大气耦合、非流体静力学、云分辨模式进行高分辨率模拟（1公里或更小），以谷脊尺度调查安第斯山脉中部地形、植被、土壤湿度和季风降雨日周期的空间格局之间的物理联系。 具体而言，将讨论以下科学问题： (1)蒸散对热带山区对流层低层能量收支日变化的贡献是什么？ 它在空间上如何随海拔和地形（山脊与山谷，迎风与背风坡，山麓与高峰）而变化？ (2)在季风期间，地形和植被的空间安排中的横向（侧向）山脉变化如何影响对流活动和降水的日循环？ (3)从卫星图像中观察到的云场多尺度行为与与地形和/或土地利用/土地覆盖模式相关的对流活动的主要空间尺度之间有何关系？ (4)目前土地使用/土地覆盖变化的趋势，特别是砍伐森林和农业活动向高地扩展，如何改变热带山区的水循环？ 这些变化对热带山区生态系统和水资源的长期可持续性有何影响？虽然在热带地区，这项工作的成果是相关的中纬度山区，特别是美国西部的地形降水（雨和雪）是占主导地位的淡水资源。最后，研究区正在经历强烈的土地利用变化，从人为消灭的自然树线，从建设的洋际公路。研究结果应能为山区可持续环境规划和适应气候多变性和变化提供更好的科学基础。