该研究是由美国陆军研究办公室奖W911NF-04-1-0169，工程技术研究开发中心（ERDC）和美国国家科学基金会资助耳1029069。此外，该研究得到一个夏令营活动在大学生研究从科罗拉多矿业学院授予。作者要感谢瑞安Tolene和保罗·舒尔特的贡献。

注意:在使用二维台架规模罐接口与气候受控风洞装置中进行实验室测试。无论是实验室规模的坦克和风洞仪表与各种传感器技术。以下协议将首先讨论的结构和制备土壤罐中，接着在风洞的和两者的仪器进行了讨论。罐的尺寸，风洞的尺寸，传感器的数量和传感器技术类型呈现可以被修改以适应一个特定的实验装置的需求。下面提出的协议被用于实验研究风速对裸土壤蒸发的影响。 1.建设和多孔介质土舱准备<ol><li>切一大块1.2厘米厚的亚克力玻璃分为五个单独的窗格。这些组装到面板的打开被冠上土罐内部长度，宽度和高度25，9.1和55厘米，RESPectively。丙烯酸玻璃允许在地下的过程被目视观察。 </li><li>画一个5×5网格上各两个大玻璃板（长25厘米，高度55厘米）25厘米×25厘米如图1。确保在网格内的每个正方形具有25平方厘米的面积（ 图1）。网格将被用于正确空间传感器的土壤罐内。 </li></ol><img alt="图1" src="/files/ftp_upload/52704/52704fig1highres.jpg" width="700" /> 图1:示意前视图和侧视图用于实验设置（尺寸以厘米）的土壤罐（a）的土壤罐的主视图显示包括25为5cm×5厘米的网格系统。广场。 （b）该土壤罐的侧视图，示出了安装温度，相对湿度和土壤湿度传感器网络作为FUNC化深度。需要注意的是原理图不按比例绘制。 <ol start="3"><li>上的大型玻璃平面之一，钻共251.9厘米（¾英寸）直径的孔的土壤湿度传感器。 <ol><li>钻每个孔中建立在步骤1.2，使得两个邻接正方形的孔的中心5厘米外网格每平方的中心;第一组孔为2.5厘米以下的槽的顶部。用适当大小的水龙头削减线程到每个新创建的孔。传感器之间5cm的间距保证了每个传感器是下一个最接近的传感器的采样体积之外。 </li></ol></li><li>同样，钻孔，挖掘步骤1.2中创建的每个网格框的中心一共有250.635厘米（¼英寸）直径的孔。确保每个孔的中心是间隔5cm与有2.5厘米以下的土壤槽的顶部的孔的第一行​​。传感器之间5cm的间距保证了各s满布的下一个最接近的传感器的采样体积之外。 </li><li>上用作罐，钻头的底部的丙烯酸窗格和自来水中的窗格中间的单个半英寸直径的孔。胶水目筛（细于要使用的测试土壤）在玻璃上的内侧的孔中。的底面上的外侧，安装附连到柔性管道具有可调阀90°弯头。该阀和管道，用于在实验终止或以此方式来安装用于保持恒定地下水位深度恒定头部设备从水箱排水。 </li><li>使用海洋级胶或类似抗水聚合物粘合剂附着并密封罐一起， 如图1。让粘合剂固化一天。 </li><li>以提高罐离地面的和使房间的90°弯头（ 图1），连接两个附加件1.2厘米厚的丙烯酸玻璃lengtH 12厘米，高5厘米到罐的底部。 </li></ol> （二）建设和温控风洞研制<ol><li>构造风洞215厘米长的上游部分出来，其具有宽度为8.5厘米，26厘米的高度的矩形镀锌钢管道材料制成。包围与聚苯乙烯绝缘管道的外部。 </li><li>钻一小孔在靠近风洞的相对湿度，温度传感器的插入的上游部的下游出口的风道的一侧（ 图2）。 </li></ol><img alt="图2" src="/files/ftp_upload/52704/52704fig2highres.jpg" width="700" /> 图2:完整实验装置，包括罐，管道系统，传感器网格（尺寸以厘米）完成合并的风洞和污垢罐装置的实验的设置。风洞是高架，坐在与土罐的表面齐平。土箱仪器与用于测量各种地下和大气变量的传感器网络。网格圆表示用于插入这些传感器的位置。加热控制系统和一个直列管风扇分别用于控制温度和风速。皮托静管是用来测量风速。整个装置坐在一个加权比例，得到的实验过程中的质量平衡。注意，示意性不按比例绘制。 <ol start="3"><li>安装定位在平行沿风洞的上游部分的长度的反射器在五个陶瓷红外加热元件。连接的红外线加热元件由红外线温度传感器调节的温度控制系统。 </li><li>构造的中间部分的风洞了两次1.2厘米厚的丙烯酸板与长度分别为25厘米和26厘米的高度。钻两个0.635厘米（¼英寸）直径的孔，在中间部分的一个面板，在图2中所示的位置中插入的温度和/或相对湿度，温度传感器。 <ol><li>固定丙烯酸板的土壤罐侧壁的顶部（ 即 ，面板尺寸为25厘米×55厘米）使用强粘合带，从而确保在风洞和土壤罐面板坐平齐彼此。 </li></ol></li><li>构造的第一个50厘米风洞的下游部分的在步骤2.1中所述的相同尺寸的矩形管道材料制成。收端，降低了矩形管道材料以15.3厘米直径的圆形导管为170厘米长。安装一个镀锌钢阻尼器，用于调节风速，在圆形管道援助在风速控制的远下游端。 </li><li>如步骤2.2，钻10.635厘米直径的孔下游矩形风管的一侧入口附近的插入一个相对湿度温度传感器。钻沿风洞的中心线的矩形管的顶部的第二0.635厘米直径的孔。 </li><li>在圆管道的中间安装直列管风扇（ 即 ，85厘米在步骤2.4中所述还原下游）定向成从所述风洞的下游部分排出空气。接口风扇具有可变速度控制器，用于旋转频率的更精确的控制，其结果风速。 </li><li>使用焊接材料和可调搁架单元提升和安全风洞设备。确保上游和下游的管道的底部是与土壤罐（ 图2）的顶部齐平。 </li></ol> 3.安装传感器<ol><li>在此之前的土壤油箱内的安装，确保一个的NPT壳体内的每个土壤湿度和温度传感器（1.9厘米0.635厘米壳体，分别）和本身与人闪密封，防止潮气侵入。不使用硅酮系的密封材料的产品，因为它们可以与某些传感器内的电子干扰。固化传感器大约一个星期。 </li><li>在安装之前在土壤罐，校准的土壤湿度传感器根据由榊等人 12开发两个点α混合方法。 </li><li>裹在安装前每个NPT外壳管道工磁带的线程在坦克，以帮助提供NPT螺纹和丙烯酸玻璃之间更好的密封。 </li><li>水平地通过罐在步骤1.2中所述的位置的壁安装共计25土壤湿度和温度的每个传感器。扭动传感器电缆同步与NPT接头/外壳以便在电缆内不会损坏内部线路。不要过度扭矩扩散条约，以防止玻璃破裂。土壤湿度传感器和温度传感器连接到其指定的数据伐木工人。 </li><li>以2.5，12.5和21.5厘米的罐的前缘的距离安装在土壤表面3相对湿度的温度传感器。放置在与土壤表面接触良好，传感器使得相对湿度读数反映在土壤表面，而不是周围的空气的条件。连接传感器数据记录器。 </li><li>以获得所需的空气的温度和相对湿度的测量在大气中，在风洞中的自由流动部安装相对湿度温度传感器，使用通过所述风洞的上游和下游的部分以及面板钻出的孔中。 </li><li>安装皮托静管通过钻在下游风洞部的顶部的0.635厘米孔直接下游土壤罐。持的皮托静压管在13厘米的部分的地板的高度。皮托静管连接到一个压差传感器。 </li><li> CalibratË差压变送器。它被定义为停滞和静态压力差的皮托静压管措施动压。压力差是由压力传感器作为电压差的解释。 <ol><li>测量无流动的状态下的电压（电压应约等于0），并且对流动的已知动态压力;这允许动态压力和电压之间建立了线性关系。确定风速运用伯努利方程: <img alt="式（1）" fo:content-width="0.8in" src="/files/ftp_upload/52704/52704eq1.jpg" width="100" /> （1） 其中，V（米/秒）是风速，P 动态 （帕）是动压，ρ（千克/米3）是空气的密度。 </li><li>比较使用等式（1）与另一测定装置计算出的速度。在这里，比较皮托静电管差压TRAnsducer用激光多普勒测速仪（LDV）的测量具有±0.01米/秒的精度。 注:采用的传感器及其相关采样频率的总结在表1中可以发现，对于传感器规格和其它信息，请参阅随附材料/设备清单。 </li></ol></li></ol><table border="0" cellpadding="0" cellspacing="0"><tbody><tr><td> 传感器 </td><td> 传感器测量 </td><td> 传感器受聘于实验装置的数 </td><td> 传感器采样频率（分钟） </td></tr><tr><td> EC-5 </td><td>土壤水分</td><td> 25 </td><td> 10 </td></tr><tr><td> ECT </td><td>土壤/空气温度</td><td> 25 </td><td> 10 </td></tr><tr><td> SH-1 </td><td>热性能</td><td> 1 </td><td> 10 </td></tr><tr><td> EHT </td><td>相对湿度/温度</td><td&gt; 5 </td><td> 10 </td></tr><tr><td>红外摄像机</td><td>表面温度/蒸发</td><td> 1 </td><td> 1 </td></tr><tr><td>数码相机</td><td>干燥前沿的可视化</td><td> 1 </td><td> 60 </td></tr><tr><td>皮托管静</td><td>风速</td><td> 1 </td><td> 10 </td></tr><tr><td>加权规模</td><td>累积蒸发/蒸发率</td><td> 1 </td><td> 10 </td></tr></tbody></table> 表1:在本研究中的实验部分使用的传感器总结。 4.包装土舱，并准备在实验开始<ol><li>之前的包装用土的罐中，通过执行泄漏测试测试其完整性。填充水的水箱，并等待4-6小时，以确保在结构或传感器没有泄漏已经开发。 <ol><li>如果泄漏开发，沥干罐，让它干燥过夜，并使用相同的米修复泄漏arine胶粘剂原施工期间使用。如果没有泄漏开发，漏土舱和下面的步骤做准备。 </li></ol></li><li>确定罐用到位传感器的总体积。使用量筒认真填写水的水箱，并确保记录的添加的水量。转换所记录的总体积为立方厘米用于步骤4.5。 </li><li>获得干土收拾土舱。分别按照在茨等人讨论的方法表征所选土壤的水力和热性能。11 </li><li>小心湿包装用土壤和去离子水的土壤罐。 <ol><li>湿-PACK土罐，先倒的水约5厘米的坦克。慢慢干燥的土壤加入到水箱中的水，用勺子，2.5 cm深的增量。记录每个电梯所以土填料的孔隙率，可以计算出时添加的砂的重量。 </li><li>完成后每一层的，反复点击使用橡胶锤，100-200倍，以获得在整个均匀松密度的罐壁。而攻，避免与传感器和传感器导线接触。应避免使用的振动装置的，以便不损坏敏感的传感器网络。 </li></ol></li><li>在包装罐，加在一起各土层的重量的完成（参见步骤4.4），以得到土壤的总质量。通过体积密度土壤划分的总质量（ 如石英砂的体积密度2.65克/厘米3），以确定砂的体积（V S，厘米3）。计算根据罐中的土壤的孔隙率（η，米3 /米3）: <img alt="公式（2）" fo:content-width="0.8in" src="/files/ftp_upload/52704/52704eq2.jpg" width="100" /> （2） 其中，（ⅤT，M 3）是在步骤4.2中确定的空槽的总体积。 </li> &lt;李&gt;一旦罐被完全填充，放置一个塑料盖如保鲜膜在罐直到实验准备开始以防止蒸发的发作。 </li><li>上放置一个加权比例罐以监测其本身又能被用于计算蒸发速率累积失水。 </li><li>除以每小时的重量损失由水的密度和蒸发表面的横截面面积的乘积计算出每小时的蒸发速率。 </li></ol> 5.启动试验，并开始数据收集<ol><li>一旦设置是完整，确定所需的大气条件（ 即温度，风速）。确保数据记录器和其它数据采集系统被接通，并设置到正确的采样间隔（ 例如 ，每10分钟）。 </li><li>启动风扇和温度控制系统。允许的气候条件对S表面上取下塑料盖之前平衡油箱。运行实验的时间所要求的长度（ 例如 ，15天）。 </li></ol>

<ol>
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Hydrol. 131 (1-4), 63-104 (1992).</li><li>Lehmann, P., Assouline, S., Or, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characteristic+lengths+affecting+evaporative+drying+of+porous+media.">Characteristic lengths affecting evaporative drying of porous media.</a> Phys. Rev. E. 77 (5 Pt 2), 056309 (2008).</li><li>Trautz, A. C., Smits, K. M., Schulte, P., Illangasekare, T. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sensible+heat+balance+and+heat-pulse+method+applicability+to+in+situ+soil-water+evaporation.">Sensible heat balance and heat-pulse method applicability to in situ soil-water evaporation.</a> Vadose Zone J. 13, (2014).</li></ol>

作者宣称，他们有没有竞争的财务权益。

该协议的目的是开发用于需要用于研究相对于热和传质过程陆地大气相互作用高空间和时间分辨率的数据的产生的实验装置和相关程序。实验装置描述由一个土壤罐和一个小风洞，两者都是配备传感器，用于有关土壤和大气变量（测量阵列的例如 ，风速，相对湿度，土壤和空气温度和土壤湿度）。下面是一些在本研究中提出的协议的最关键部件。 罐的尺寸和传感器的?...

了解陆地和大气之间的相互作用是极为重要的我们的许多当前世界问题，如地质，封存二氧化碳的土壤中渗出，气候变化，水和食物供应，准确的检测地雷的认识，和地下水的修复和土壤。此外，热和水的初级交流驱动的全球和区域的气象条件发生在地球表面。许多天气和气候现象（ 如飓风，厄尔尼诺＆＃241; O，干旱等 ）主要通过大气，陆面相互作用1相关的流程驱动的。由于超过一半的土地表面在地球上的是干旱或半干旱2-4，准确地描述的热和水交换的大气和土壤表面之间的基础上，水循环在这些区域是改进我们的理解临界上述问题，特别是在地区容易受到持续干旱和荒漠化。然而，尽管几十年的研究，仍然存在许多知识缺口在如何浅层地下和大气相互作用5目前了解。 涉及液体水，水蒸汽和热量在土壤运输过程是动态的，强耦合相 ​​对于与土壤相互作用和强迫边界条件（ 即 ，温度，相对湿度，热辐射）。数值传热传质模型通常过于简单或忽视了一些这些复杂的部分缺乏检测和高时空分辨率数据的缺乏导致现有理论的精细化所致。为模型验证开发数据集常常缺乏关键的大气或地下信息正确测试理论，导致数值模型不正确地考虑进口蚂蚁过程或依赖于使用被调整或装配在模型知之甚少参数。这种方法被广泛地由于其使用简单和容易使用的，并具有所示的多优点的一些应用。但是，这种方法可以在由通过执行，其能够检测热和水传递理论6的瞬态条件下很好地控制实验更好地理解后面这些"集总参数化"的物理改善。 仔细的实验​​在实验室允许产生精确的数据集随后可以用来验证数值模型。购自字段站点数据往往是不完整和昂贵，获得，和控制的程度需要获得的处理的基本了解，并产生用于模型验证数据在某些情况下可能被认为是不够的。自然现象如土壤蒸发实验实验室允许ATMOSpheric条件（ 即 ，温度，相对湿度，风速）和土壤条件（ 即 ，土壤类型，孔隙率，填料配置）来小心地控制。用于研究土壤蒸发和土壤热和水力性能众多的实验室技术使用破坏性取样7-10。破坏性取样方法需要土壤样品进行解压，以获得点数据，防止瞬态行为的测量和破坏土壤的物理性质;这种方法引入的错误和不确定性的数据。无损测量，如这里介绍的方法，允许对土壤性质的相互依存更加准确地测定和研究，并处理11。 这项工作的目标是开发一种土壤罐装置和相关的协议对高时空分辨率的数据的有关在大气变化和地下条件的影响的代裸土蒸发。对于这项工作，能够保持恒定的风速和温度的小风洞接口与一个土壤罐装置。风洞和土舱仪表都带有一套最先进的传感器技术，自主和连续数据采集的状态。风速是使用附连到压力传感器的不锈钢皮托静管测量。温度和相对湿度在使用两种类型的传感器的气氛进行监控。相对湿度和温度也监视在土壤表面。传感器在地下测量土壤湿度和温度。罐装置的重量的测量被用来通过水的质量平衡，以确定蒸发。为了证明这一点的实验装置和协议的适用性，我们提出在变化的风速条件裸土壤蒸发的一个例子。土罐，具有良好表征沙均匀包装，最初是完全SAturated并允许自由地仔细控制的大气条件下蒸发（ 即温度，风速）。

<table><tbody><tr><td>ECH2O EC-5 Soil Moisture Sensor (25)</td><td>Decagon Devices Inc. Decagon.com</td><td>40593</td><td>For specifics visit: http://www.decagon.com/products/soils/volumetric-water-content-sensors/ec-5-soil-moisture-small-area-of-influence/. Sampling frequency on 10 minute intervals, accuracy is &amp;plusmn;3%, and collect data using the Em50 dataloggers</td></tr><tr><td>ECT Soil/Air Temperature Sensor (19)</td><td>Decagon Devices Inc. Decagon.com</td><td>40651</td><td>For specifications visit http://www.decagon.com/products/canopy-atmosphere/temperature/ect-air-temperature/. Sampling frequency on 10 min intervals, accuracy is &amp;plusmn;0.5&amp;nbsp;&amp;deg;C, Measure within a temperature of 5 and 40&amp;nbsp;&amp;deg;C, and collect data using the Em50 dataloggers</td></tr><tr><td>EHT Relative Humidity and Temperature Sensor (5)</td><td>Decagon Devices Inc. Decagon.com</td><td>N/A</td><td>Sampling Frequency on 10 min intervals, accuracy is &amp;plusmn;3% between 5% and 100% relative humidity, and collect data using Em50 data loggers. For more information visit decagon.com</td></tr><tr><td>Em50 Data Logger (10)</td><td>Decagon Devices Inc. Decagon.com</td><td>40800</td><td>For specifics visit http://www.decagon.com/products/data-management/data-loggers/em50-digital-analog-data-logger/. ECH2O decagon devices, pulls data from the ECT, EC-5, and EHT sensors, and each data logger has 5 sensor connections and a com port that connects from the logger to USB to computer</td></tr><tr><td>Sartorius Weighing Scale (1)</td><td>Sartorius Corporation</td><td>11209-95</td><td>Sartorius Model 11209-95, Range = 65&amp;nbsp;kg, Resolution = &amp;plusmn;1&amp;nbsp;g</td></tr><tr><td>Infrared SalamandernCeramic Radiative Heater (1)</td><td>Mor Electric Heating Assoc., Inc. http://www.morelectricheating.com/</td><td>FTE 500-240</td><td>5 heaters needed, adjust to get the right ambient/free-flow temperature</td></tr><tr><td>2104 Temperature Control System (1)</td><td>Chromalox</td><td>2104</td><td>Controls the heaters
&lt;br /&gt;&amp;#160;&lt;br /&gt;&amp;#160;&lt;br /&gt;&amp;#160;&lt;br /&gt;&amp;#160;&lt;br /&gt;&amp;#160;&lt;br /&gt;&amp;#160;</td></tr><tr><td>Infrared Temperature Sensor Regulator (1)</td><td>Exergen Corporation</td><td>N/A</td><td>Monitors the heaters temperatures</td></tr><tr><td colspan="4">[header]</td></tr><tr><td>Stainless Steel Pitot-Static Tube (1)</td><td>Dwyer Instruments, Inc. http://www.dwyer-inst.com/</td><td>Series 160</td><td>For specifics visit http://www.dwyer-inst.com/Product/%20TestEquipment/PitotTubes/Series160. Sensor sampling frequency is every 10 minutes, must be connected to differential pressure transducer and anemometer, and convert the pressure data collected into win velocities using Bernoulli&#039;s equation.</td></tr><tr><td>1/2 inch Acrylic (1)</td><td>Colorado Plastics http://www.coloradoplastics.com/</td><td>N/A</td><td>Specific heat of 1,464&amp;nbsp;J&amp;nbsp;kg&lt;sup&gt;-1&lt;/sup&gt;&amp;nbsp;K&lt;sup&gt;-1&lt;/sup&gt;, thermal conductivity of 0.2&amp;nbsp;W&amp;nbsp;m&lt;sup&gt;-1&lt;/sup&gt;&amp;nbsp;K&lt;sup&gt;-1&lt;/sup&gt;, and a density of 1,150&amp;nbsp;kg&amp;nbsp;m&lt;sup&gt;-3&lt;/sup&gt;</td></tr><tr><td>Galvanized Steel Ducting Material (1)</td><td>Home Depot</td><td>N/A</td><td>Material used to build wind- tunnel, and both round and rectangular ducting were used in construction and connected using square-to-round reducer duct</td></tr><tr><td>Variable Speed Controller Connected to an In-Line Duct Fan (1)</td><td>Suncourt, Inc. http://www.suncourt.com/</td><td>VS200</td><td>15.3 cm in Diameter Placed in-line with round duct</td></tr><tr><td>Galvanized Steel Damper (1)</td><td>Home Depot</td><td>N/A</td><td>Used to control/reduce speeds in the wind tunnel for low velocity data</td></tr><tr><td>Accusand #30/40 (1)</td><td>Unimin Corporation http://www.unimin.com/</td><td>N/A</td><td>This sand is silica sand and is 99.8% quartz, its grain shape is classified as rounded, the uniformity coefficient is approximately 1.2, and the grain density is 2.66&amp;nbsp;g/cm&lt;sup&gt;3&lt;/sup&gt;.</td></tr></tbody></table>

exploring the effects of atmospheric forcings on evaporation: experimental integration of the atmospheric boundary layer and shallow subsurface

Evaporation is directly influenced by the interactions between the atmosphere, land surface and soil subsurface. This work aims to experimentally study evaporation under various surface boundary conditions to improve our current understanding and characterization of this multiphase phenomenon as well as to validate numerical heat and mass transfer theories that couple Navier-Stokes flow in the atmosphere and Darcian flow in the porous media. Experimental data were collected using a unique soil tank apparatus interfaced with a small climate controlled wind tunnel. The experimental apparatus was instrumented with a suite of state of the art sensor technologies for the continuous and autonomous collection of soil moisture, soil thermal properties, soil and air temperature, relative humidity, and wind speed. This experimental apparatus can be used to generate data under well controlled boundary conditions, allowing for better control and gathering of accurate data at scales of interest not feasible in the field. Induced airflow at several distinct wind speeds over the soil surface resulted in unique behavior of heat and mass transfer during the different evaporative stages.

这里介绍的实验的目的是研究风速对蒸发裸土的效果。在本研究中使用的测试土壤的关键性质总结于表2中 。进行了一系列的实验，其中在土壤表面（ 即 ，风速和温度）不同的边界条件被应用（ 表3）。虽然四个实验在不同的风速和温度进行，多数实验结果这里提出是1.22米/秒的风速。累积蒸发数据显示所有四个实验。 <table border="0" cellpadding="0" cellspacing="0"><tbody...

Watch this Scientific Journal Video about Exploring the Effects of Atmospheric Forcings on Evaporation: Experimental Integration of the Atmospheric Boundary Layer and Shallow Subsurface at JoVE.com

Exploring the Effects of Atmospheric Forcings on Evaporation: Experimental Integration of the Atmospheric Boundary Layer and Shallow Subsurface

一种协议，用于土壤罐接口到小气候控制风洞，研究大气蒸发强迫的影响的设计和施工方法。无论是土坦克和风洞仪表与传感器技术， 在环境条件原位测量持续。

在探索大气蒸发强迫的影响:大气边界层和浅地层的实验整合

Evaporation is directly influenced by the interactions between the atmosphere, land surface and soil subsurface. This work aims to experimentally study ...

exploring-effects-atmospheric-forcings-on-evaporation-experimental

Universidad de Cartagena UDEC

Research

Education

JoVE Core

JoVE Journal

Civil Engineering

Environment

Unit 1

Leveling

SCIENTISTS IN ACTION

8.6K 次观看.  Colorado School of Mines. 一种协议，用于土壤罐接口到小气候控制风洞，研究大气蒸发强迫的影响的设计和施工方法。无论是土坦克和风洞仪表与传感器技术， 在环境条件原位测量持续。 

视频: Exploring the Effects of Atmospheric Forcings on Evaporation: Experimental Integration of the Atmospheric Boundary Layer and Shallow Subsurface

Surface Renewal: An Advanced Micrometeorological Method for Measuring and Processing Field-Scale Energy Flux Density Data

Advanced micrometeorological methods have become increasingly important in soil, crop, and environmental sciences. For many scientists without formal training in atmospheric science, these techniques are relatively inaccessible. Surface renewal and other flux measurement methods require an understanding of boundary layer meteorology and extensive training in instrumentation and multiple data management programs. To improve accessibility of these techniques, we describe the underlying theory of surface renewal measurements, demonstrate how to set up a field station for surface renewal with eddy covariance calibration, and utilize our open-source turnkey data logger program to perform flux data acquisition and processing. The new turnkey program returns to the user a simple data table with the corrected fluxes and quality control parameters, and eliminates the need for researchers to shuttle between multiple processing programs to obtain the final flux data. An example of data generated from these measurements demonstrates how crop water use is measured with this technique. The output information is useful to growers for making irrigation decisions in a variety of agricultural ecosystems. These stations are currently deployed in numerous field experiments by researchers in our group and the California Department of Water Resources in the following crops: rice, wine and raisin grape vineyards, alfalfa, almond, walnut, peach, lemon, avocado, and corn.

Surface renewal is a micrometeorological method that is being used increasingly to determine energy fluxes, but its technical complexity makes it inaccessible to a broad audience. We describe the steps needed to set up and calibrate a surface renewal field station, to acquire and process data, and to correctly interpret results.

表面重建:一种先进的微气象法测量和处理油田规模能流密度数据

Advanced micrometeorological methods have become  increasingly important in soil, crop, and environmental sciences.  For many scientists without formal ...

科研

环境科学

Measurements of CO2 Fluxes at Non-Ideal Eddy Covariance Sites

This protocol is an example of utilizing the eddy covariance (EC) technique to investigate spatially and temporally averaged net CO2 fluxes (net ecosystem production, NEP), in non-typical ecosystems, on a currently reforested windthrow area in Poland. After a tornado event, a relatively narrow &#8220;corridor&#8221; was created within surviving forest stands, which complicates such kind of experiments. The application of other measuring techniques, such as the chamber method, is even more difficult under these circumstances, because especially at the beginning, fallen trees and in general great heterogeneity of the site provide a challenging platform to perform flux measurements and then to properly upscale obtained results. In comparison with standard EC measurements carried out in untouched forests, the case of windthrow areas requires special consideration when it comes to the site location and data analysis in order to ensure their representativeness. Therefore, here we present a protocol of real-time, continuous CO2 flux measurements at a dynamically changing, non-ideal EC site, which includes (1) site location and instrumentation setup, (2) flux computation, (3) rigorous data filtering and quality control, and (4) gap filling and net fluxes partitioning into CO2 respiration and absorption. The main advantage of the described methodology is that it provides a detailed description of the experimental setup and measurement performance from scratch, which can be applied to other spatially limited ecosystems. It can also be viewed as a list of recommendations on how to deal with unconventional site operation, providing a description for non-specialists. Obtained quality-checked, gap filled, half-hour values of net CO2, as well as absorption and respiration fluxes, can be finally aggregated into daily, monthly, seasonal or annual totals.

Measurements of CO2 Fluxes at Non-Ideal Eddy Covariance Sites

The presented protocol uses the eddy covariance method at non-typical locations, applicable to all types of short-canopy ecosystems with limited area, on a currently reforested windthrow site in Poland. Details of measuring site setup rules, flux calculations and quality control, and final result analysis, are described.

非理想涡流位点的 CO2通量测量

This protocol is an example of utilizing the eddy covariance (EC) technique to investigate spatially and temporally averaged net CO2 fluxes (net ecosystem ...

Measurements of Waves in a Wind-wave Tank Under Steady and Time-varying Wind Forcing

This manuscript describes an experimental procedure that allows obtaining diverse quantitative information on temporal and spatial evolution of water waves excited by time-dependent and steady wind forcing. Capacitance-type wave gauge and Laser Slope Gauge (LSG) are used to measure instantaneous water surface elevation and two components of the instantaneous surface slope at a number of locations along the test section of a wind-wave facility. The computer-controlled blower provides airflow over the water in the tank whose rate can vary in time. In the present experiments, the wind speed in the test section initially increases quickly from rest to the set value. It is then kept constant for the prescribed duration; finally, the airflow is shut down. At the beginning of each experimental run, the water surface is calm and there is no wind. Operation of the blower is initiated simultaneously with the acquisition of data provided by all sensors by a computer; data acquisition continues until the waves in the tank fully decay. Multiple independent runs performed under identical forcing conditions allow determining statistically reliable ensemble-averaged characteristic parameters that quantitatively describe wind-waves&#39; variation in time for the initial development stage as a function of fetch. The procedure also allows characterizing the spatial evolution of the wave field under steady wind forcing, as well as decay of waves in time, once the wind is shut down, as a function of fetch.

This manuscript describes a fully computer-controlled procedure that allows obtaining reliable statistical parameters from experiments of water waves excited by steady and unsteady wind forcing in a small-scale facility.

稳定时变风强迫下风浪罐中波浪的测量

This manuscript describes an experimental procedure that allows obtaining diverse quantitative information on temporal and spatial evolution of water ...

工程学

<meta charset="utf8"></head><body>通过蒸发测量土壤水力特性的协议

Measurements of Soil Water Potential and Conductivity based on a Simple Evaporation Experiment using a Hydraulic Property Analyzer

The measurement of soil hydraulic properties is critical in understanding the physical components of soil health as well as integrated knowledge of soil systems under various management practices. Collecting reliable data is imperative for informing decisions that affect agriculture and the environment. The simple evaporation experiment described here uses instrumentation in a laboratory setting to analyze soil samples collected in the field. The soil water tension of the sample is measured by the instrument, and tension data is modeled by software to return soil hydraulic properties. This method can be utilized to measure soil water retention and hydraulic conductivity and give insight into differences in treatments or environmental dynamics over time. Initial establishment requires a user, but data acquisition is automated with the instrument. Soil hydraulic properties are not easily measured with traditional experiments, and this protocol offers a simple and optimal alternative. Interpretation of results and options for extending the data range are discussed.

<meta charset="utf8"></head><body>作者聚焦:使用水力特性分析仪推进农业用地生态系统研究以评估土壤健康状况

This article features a simple evaporation experiment using a hydraulic property instrument for a soil sample. Through efficient means, measurements can be taken over a series of days to generate high-quality data.

使用水力特性分析仪基于简单蒸发实验的土壤水势和电导率测量

The measurement of soil hydraulic properties is critical in understanding the physical components of soil health as well as integrated knowledge of soil ...

Measurement of Leaf Hydraulic Conductance and Stomatal Conductance and Their Responses to Irradiance and Dehydration Using the Evaporative Flux Method (EFM)

Water is a key resource, and the plant water transport system sets limits on maximum growth and drought tolerance. When plants open their stomata to achieve a high stomatal conductance (gs) to capture CO2 for photosynthesis, water is lost by transpiration1,2. Water evaporating from the airspaces is replaced from cell walls, in turn drawing water from the xylem of leaf veins, in turn drawing from xylem in the stems and roots. As water is pulled through the system, it experiences hydraulic resistance, creating tension throughout the system and a low leaf water potential (&Psi;leaf). The leaf itself is a critical bottleneck in the whole plant system, accounting for on average 30% of the plant hydraulic resistance3. Leaf hydraulic conductance (Kleaf = 1/ leaf hydraulic resistance) is the ratio of the water flow rate to the water potential gradient across the leaf, and summarizes the behavior of a complex system: water moves through the petiole and through several orders of veins, exits into the bundle sheath and passes through or around mesophyll cells before evaporating into the airspace and being transpired from the stomata. Kleaf is of strong interest as an important physiological trait to compare species, quantifying the effectiveness of the leaf structure and physiology for water transport, and a key variable to investigate for its relationship to variation in structure (e.g., in leaf venation architecture) and its impacts on photosynthetic gas exchange. Further, Kleaf responds strongly to the internal and external leaf environment3. Kleaf can increase dramatically with irradiance apparently due to changes in the expression and activation of aquaporins, the proteins involved in water transport through membranes4, and Kleaf declines strongly during drought, due to cavitation and/or collapse of xylem conduits, and/or loss of permeability in the extra-xylem tissues due to mesophyll and bundle sheath cell shrinkage or aquaporin deactivation5-10. Because Kleaf can constrain gs and photosynthetic rate across species in well watered conditions and during drought, and thus limit whole-plant performance they may possibly determine species distributions especially as droughts increase in frequency and severity11-14.
We present a simple method for simultaneous determination of Kleaf and gs on excised leaves. A transpiring leaf is connected by its petiole to tubing running to a water source on a balance. The loss of water from the balance is recorded to calculate the flow rate through the leaf. When steady state transpiration (E, mmol &bull; m-2 &bull; s-1) is reached, gs is determined by dividing by vapor pressure deficit, and Kleaf by dividing by the water potential driving force determined using a pressure chamber (Kleaf= E /- &Delta;&psi;leaf, MPa)15.
This method can be used to assess Kleaf responses to different irradiances and the vulnerability of Kleaf to dehydration14,16,17.

Measurement of Leaf Hydraulic Conductance and Stomatal Conductance and Their Responses to Irradiance and Dehydration Using the Evaporative Flux Method EFM

We describe a relatively rapid (30 min) and realistic method for simultaneously measurement of leaf hydraulic conductance (Kleaf) and stomatal conductance (gs) for transpiring excised leaves. The method can be modified to measure the light and dehydration responses of Kleaf and gs.

测量叶片导水率和气孔导度和他们的反应，辐射和脱水蒸发通量法（EFM）

Water is a key resource, and the plant water transport system sets limits on maximum growth and drought tolerance. When plants open their stomata to ...

生物学

Boundary Layer Characteristics

When a fluid encounters a solid surface, a boundary layer forms due to the interaction between the fluid's motion and the stationary surface. This phenomenon is characterized by a thin region adjacent to the surface where viscous forces dominate, influencing the fluid's velocity profile. The development of the boundary layer begins at the leading edge of the surface and evolves as the fluid moves downstream.As the fluid flows over the surface, friction between the fluid and the wall slows down the particles nearest the surface. This effect creates a velocity gradient, where the velocity of the fluid increases from zero at the wall to the free-stream velocity farther away. The region where this velocity gradient exists defines the boundary layer. Over distance, the thickness of the boundary layer increases as more fluid is affected by the surface's resistance.In the region close to the leading edge, the boundary layer is typically laminar. Here, fluid particles move in smooth, parallel layers with minimal mixing. The flow remains stable under certain conditions, but as it progresses downstream, factors such as surface roughness, velocity increases, or pressure gradients can destabilize the flow. Once the flow reaches a critical Reynolds number, the laminar boundary layer transitions to a turbulent state. The turbulent boundary layer is characterized by chaotic mixing of fluid particles, increased energy dissipation, and a thicker boundary layer compared to its laminar counterpart.The laminar boundary layer's velocity profile can be described mathematically using the Blasius equation, a solution to the Navier-Stokes equations under specific assumptions. For practical applications, the Momentum Integral Boundary Layer equation provides a way to analyze momentum changes in the boundary layer without requiring a detailed velocity profile. These models are critical for understanding fluid dynamics near surfaces, particularly in engineering and aerodynamic applications.

When a fluid encounters a solid surface, a boundary layer forms due to the interaction between the fluid's motion and the stationary surface. This ...

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Flow over Immersed Bodies

KEY TERMS AND CONCEPTS

Variation of Atmospheric Pressure

Change in atmospheric pressure with height is particularly interesting. The decrease in atmospheric pressure with increasing altitude is due to the decreasing gravitational force per unit area as we move away from the surface of the earth.
Assuming the air temperature is constant at a given altitude and that the ideal gas law of thermodynamics describes the atmosphere to a good approximation, one can find the variation of atmospheric pressure with height.
Let p(y) be the atmospheric pressure at height y. The density &#961; at y, the temperature T in the Kelvin scale (K), and the mass m of a molecule of air are related to the absolute pressure by the ideal gas law, in the form:
<img alt="Equation1" src="/files/ftp_upload/14711/14711_Equation_1.svg" style="text-align: center; height: 38px;" />
Using density from the ideal gas law, the rate of variation of pressure with height is integrated from sea level, and the final expression is obtained as:
<img alt="Equation2" src="/files/ftp_upload/14711/14711_Equation_2.svg" style="text-align: center; height: 17px;" />
where,
<img alt="Equation3" src="/files/ftp_upload/14711/14711_Equation_3.svg" style="text-align: center; height: 38px;" />
Atmospheric pressure drops exponentially with height, since the y-axis points up from the ground, and y has positive values in the atmosphere above sea level. The pressure drops by a factor of 1/e when the height is 1/&#945;, which gives us a physical interpretation for &#945;. The constant 1/&#945; is a length scale that characterizes how pressure varies with height and is often referred to as the pressure scale height.

大气压力的变化

Change in atmospheric pressure with height is particularly interesting. The decrease in atmospheric pressure with increasing altitude is due to the ...

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Physics

Fluid Mechanics

关键术语与概念

Influence of Earth's Curvature and Atmospheric Refraction on Leveling

During leveling, the Earth's curvature and atmospheric refraction introduce deviations in the line of sight from a true horizontal reference.&nbsp;When the line of sight is leveled, it remains perpendicular to the plumb line only at a single point. Beyond this, it deviates due to the Earth’s curvature, represented by the correction C. For a sight distance D, the deviation can be derived using the relationship:<figure class="image image-style-align-center image_resized" style="display:table;margin-left:auto;margin-right:auto;width:9.53%;"><img style="aspect-ratio:197/150;" src="https://cloudfront.jove.com/files/ftp_upload/18021/18021_Equation_1_editor_18021.svg" alt="18021_Equation_1.svg"></figure>This relationship shows that the deviation increases quadratically with distance. Over a horizontal distance of 1 kilometer, it is approximately 0.0785 meters.In addition to curvature, atmospheric refraction bends the line of sight downward, further deviating it from the true horizontal. The bending effect is approximately one-seventh of the Earth's curvature deviation, amounting to about 0.0112 meters over 1 kilometer. This refraction arises from variations in the refractive index of air with altitude, causing light rays to curve slightly.&nbsp;The combined influence of Earth's curvature and atmospheric refraction is approximately 0.0675 meters over 1 kilometer. As with curvature alone, this combined effect increases with the square of the distance, which requires careful adjustments during leveling operations to maintain accuracy. Correcting for these deviations is critical for high-precision applications, such as determining benchmark elevations and establishing horizontal planes over long distances.

During leveling, the Earth's curvature and atmospheric refraction introduce deviations in the line of sight from a true horizontal reference.&nbsp;When ...

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Boundary Layer Characteristics

大气压力的变化

Influence of Earth's Curvature and Atmospheric Refraction on Leveling