CAREER: The onset of the rainy season in Amazonia

亚马逊河流域被称为“绿色海洋”，这个词的灵感来自其茂密的森林树冠的翡翠广阔。 在雨季，这种类比具有物理意义，因为雨水主要福尔斯中层积云，类似于热带海洋上常见的积云。 此外，森林表面提供了丰富的水分来源来维持云，在海洋对流中扮演着与海洋表面相同的角色。 但是PI之前的研究表明，在旱季结束时，这种类比就失效了，云看起来更像是在干燥的草原上形成的积云塔。 地面也起着不同的作用，因为深云是由对流可用位能的高值触发的，地面主要是作为建立对流可用位能的热源，而不是水分来源。首席研究员（PI）考虑了植物生理学在发病前季节云形成中所起的作用（也称为过渡季节）。干旱季节结束时，水分胁迫是常见的，处于水分胁迫下的植被保持水分，导致地表升温，促进CAPE升高。 另一方面，云需要水蒸气来源，可以通过邻近土壤仍然潮湿的地区的植物蒸腾来提供水蒸气。 因此，PI假设，在水胁迫地区，由表面加热引起的上升运动从低水胁迫地区吸收水分（植物将水分蒸发到空气中），因此植物水分胁迫高低之间的梯度在雨季开始时促进对流方面起着关键作用。该研究使用了来自卫星遥感和气象再分析产品等来源的观测数据，连同数值模拟，以涵盖各种现象和空间尺度，将植物生理学与云和降水联系起来。 一个关键的数据来源是来自卫星的太阳能诱导荧光（SIF），这是一种由暴露在阳光下的植物中的叶绿素发出的微妙和特定波长的辉光。 以前的研究表明，当植物处于水分胁迫下时，SIF会下降，因此来自卫星的SIF可以用来绘制亚马逊地区水分胁迫的空间梯度。该CAREER奖的教育部分侧重于向服务不足和代表性不足的人群中的K-12和大学生提供服务。 在大学一级，PI与领导联盟夏季研究早期识别计划合作，为少数民族服务机构的本科生提供夏季实习机会。K-12教育是与普罗维登斯公立学校合作解决的，这些学校为很高比例的西班牙裔和非洲裔美国学生提供服务。PI的团队与PPS官员合作，为小学和中学教师组织夏季研讨会，帮助他们创建和实施关于天气，气候和生态系统相互作用的课程模块。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Amazon basin has been called the "Green Ocean", a term inspired by the emerald expanse of its dense forest canopy. In the rainy season the analogy has physical significance as the rain falls primarily from mid-depth cumulus clouds which resemble those commonly found over tropical oceans. Also, the forested surface provides an abundant source of moisture to sustain the clouds, playing the same role as the ocean surface in maritime convection. But prior work by the PI shows that at the end of the dry season the analogy breaks down and clouds look more like the cumulus towers that form over dry grasslands. The surface also plays a different role, as the deep clouds are triggered by high values of convective available potential energy (CAPE), and the surface serves primarily as a heat source to build CAPE rather than a moisture source.Recognizing the differing roles of moist and dry land surface, the principal investigator (PI) considers the role played by plant physiology in cloud formation during the pre-onset season (also referred to as the transition season). Water stress is common at the end of the dry season and vegetation under water stress retains moisture, causing the surface to heat up and promoting higher CAPE. On the other hand clouds need a source of water vapor, which can be supplied by plant transpiration in adjacent regions where the soil is still moist. Thus the PI hypothesizes that rising motion induced by surface heating over water stressed regions draws in moisture from regions of low water stress (where plants transpire moisture into the air), so that the gradient between high and low plant water stress plays a key role in promoting convection at the onset of the rainy season.The research uses observational data from sources including satellite remote sensing and meteorological reanalysis products, together with numerical simulations, to cover the range of phenomena and spatial scales linking plant physiology with clouds and precipitation. One key data source is satellite-derived Solar Induced Fluorescence (SIF), a subtle and wavelength-specific glow emitted by chlorophyll in plants exposed to sunlight. Previous studies have shown that SIF declines when plants are under water stress, thus SIF from satellites can be used to map the spatial gradient of water stress over the Amazon.The educational component of this CAREER award focuses on outreach to K-12 and college students from underserved and underrepresented populations. At the college level the PI works with the Leadership Alliance Summer Research Early Identification Program to provide summer internships for undergraduates from minority serving institutions. K-12 education is addressed in collaboration with the Providence Public Schools (PPS), which serve a high percentage of Hispanic and African American students. The PI's team works with PPS officials to organize summer workshops for elementary and middle school teachers to assist them in creating and implementing lesson modules on weather, climate and ecosystem interactions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.