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

山脉为世界60%以上的人口提供淡水，因此地形降水的位置和时间对决定水资源和生态系统服务的可用性和用途至关重要。山地系统还拥有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化和变化的反应严重依赖于云和降水制度。这项提议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地区地形云和降水的时空变异性，热带高山是生物多样性保护和人类供水的高度优先地区。中心的研究假设是，蒸散是大气边界层(ABL)的关键水汽来源，无论是本地的还是远程的，通过昼夜山谷环流的湿输送，在下午的高海拔地区降低云底，并在可降水量和对流可用势能(CAPE)达到夜间最大配置的地貌位置加强热力不稳定。因此，云和降水组织的空间模式应通过植被和土壤水分模式在海拔梯度上的空间变异性以及这如何转化为陆地表面和对流层低层之间潜热通量日循环的空间变异性来解释。为了评估这一假设，这项研究将重点放在秘鲁中部安第斯山脉的热带山地云雾森林上，利用安第斯生物多样性和生态系统研究小组(ABERG)正在进行的多学科、多机构的生态学研究，该小组包括英国的爱丁堡大学和牛津大学，以及美国的FIT、维克森林和杜克大学等。ABERG安装了以科斯尼帕塔山谷为中心的大量植被地块和相关的生态系统功能测量，从高安第斯山脉延伸到亚马逊低地。该小区网络由一系列21个绘制、测量和担保的1公顷树地组成，包括约15,000个树干。这些地块嵌入了一系列现有的气象站和数据记录器，范围从3450米到250米不等。这些公顷的样地也构成了密集的生态系统功能实验的基础，主要样带沿线的样地在分层随机抽样中选择的20%的树木上安装了树干测量仪。还对样地的子集进行了叶、果和细根生产力、森林结构和叶面积指数的研究，并记录了土壤水分、林下和冠层光照水平、降雨量、风速和风向。对光合作用、叶片、茎和土壤呼吸的碳循环测量也在这些地块进行。3000米高的密集水文研究地块也被用于穿透雨、树干径流和云截留的测量。这项调查依靠诊断过程研究，结合卫星产品和来自现有和扩大的网络的地面观测，调查水文生态地貌状况和云量之间的时空关系。将使用陆地-大气、非静力、云分辨耦合模式进行高分辨率(1公里或更小)模拟，以研究地形、植被、土壤湿度的空间格局与安第斯山脉中部谷脊尺度的季风降雨日循环之间的物理联系。具体而言，将讨论下列科学问题：(1)蒸散对热带山区对流层低层能量收支的日循环有何贡献？(2)地形和植被空间布局的横向(横向)变化如何影响季风期间对流活动和降水的日循环？(3)从卫星图像观测到的云场的多尺度行为与主要的对流活动空间尺度之间的关系是什么？或土地利用/土地覆盖模式？(4)目前的土地利用/土地覆盖变化趋势，特别是毁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，这项工作的结果与中纬度山区有关，特别是美国西部，那里的地形降水(雨和雪)是主要的淡水资源。最后，研究区域正在经历强烈的土地利用变化，从人为消除天然林线，到建设大洋间公路。研究结果应有助于改善山区可持续环境规划和适应气候多变和变化的科学基础。

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.