Mesoscale Vegetation-atmosphere Feedbacks

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。土地是气候系统的组成部分，土地覆盖的变化可以显着影响陆地天气和气候。该项目旨在研究巴西亚马逊西南部朗多尼亚州森林砍伐背景下季节性时间尺度上区域尺度的植被-大气反馈。高速公路和二级公路沿线的森林砍伐沿着形成了独特的“鱼骨”模式，迫使类似于海风的有组织的中尺度环流，通常被称为“植被风”。“这些植被风影响当地的水文气象学，增强了森林砍伐区的积云和对流降水。该项目将检验朗多尼亚的森林砍伐通过大气途径对自身产生负反馈的假设。鱼骨状森林砍伐的水文气象影响在干旱和过渡季节最为突出，在这一季节，过量的降雨可以促进森林砍伐地区的植物生长。这是一种负反馈，因为被砍伐的小块土地上植被的加速恢复部分地补偿了砍伐森林的影响。本项目还将研究背景水文气象学在植被-大气反馈过程中的作用。特别是，它将调查系统是否表现出阈值行为，即，如果背景温度、降水量和云量超过某些阈值，对毁林的反应是否可以从消极（自我修复）转变为积极（失控）反馈。将使用植物生长模型进行敏感性研究，以估计这些阈值的大小（如果存在）。这将是关于生物圈-大气耦合系统中植被-大气中尺度反馈的第一批研究之一-在空间上是区域性的，在时间上是季节性的，从而填补了湍流和气候尺度之间的光谱空白。该项目将支持和培训一名博士生和一名本科实习生开发动态植被模型的Java版本。该模型将被用作一门课程中的动手工具，供学生进行简单的数值实验，并探索驱动生物圈-大气相互作用的关键过程。它将有助于在2008年秋季开始在伊利诺伊大学的大气科学新的本科专业的研究和教学课程。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Land is an integral component of the climate system and changes in land cover can significantly influence terrestrial weather and climate. This project aims to investigate regional-scale vegetation-atmosphere feedbacks over seasonal timescales in the context of deforestation in Rondonia, a Brazilian state in southwestern Amazonia.Deforestation along highways and secondary roads has created a unique "fishbone" pattern that forces organized mesoscale circulations similar to sea-breezes, often referred to as "vegetation breezes." These vegetation breezes affect local hydrometeorology, enhancing cumulus clouds and convective precipitation over the deforested patches. This project will test the hypothesis that deforestation in Rondonia exerts a negative feedback on itself via the atmospheric pathway. The hydrometeorological effects of fishbone deforestation are most prominent during the dry and transition seasons when excess rainfall can enhance plant growth over deforested regions. This constitutes a negative feedback because accelerated vegetation recovery over deforested patches partially compensates for the effects of deforestation. This project will also study the role of background hydrometeorology in the vegetation-atmosphere feedback process. In particular, it will investigate if the system exhibits threshold behavior, i.e., whether the response to deforestation can switch from a negative (self-healing) to a positive (runaway) feedback if the background temperature, precipitation and cloud cover exceed certain threshold values. Sensitivity studies will be conducted with a plant growth model to estimate the magnitudes of these thresholds, if present. This will be among the first studies on vegetation-atmosphere mesoscale feedbacks in the coupled biosphere-atmosphere system over an intermediate scale - regional in space and seasonal in time, thereby filling the spectral gap between the turbulence and climate scales. The project will support and train a Ph.D student and also an undergraduate intern to develop the java-version of the dynamic vegetation model. This model will be used as a hands-on tool in a course for students to conduct simple numerical experiments and explore key processes driving biosphere-atmosphere interactions. It will contribute to the research and teaching curriculum of the new Undergraduate Major in Atmospheric Sciences starting in the fall of 2008 at the University of Illinois.