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
概要
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。
Abstract
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.
Introduction
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）。
Protocol
Representative Results
Discussion
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?…
開示
The authors have nothing to disclose.
Acknowledgements
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。
Materials
| ECH2O EC-5 Soil Moisture Sensor (25) | Decagon Devices Inc. Decagon.com | 40593 | 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 ±3%, and collect data using the Em50 dataloggers |
| ECT Soil/Air Temperature Sensor (19) | Decagon Devices Inc. Decagon.com | 40651 | For specifications visit http://www.decagon.com/products/canopy-atmosphere/temperature/ect-air-temperature/. Sampling frequency on 10 minute intervals, accuracy is ±0.5°C, Measure within a temperature of 5 and 40°C, and collect data using the Em50 dataloggers |
| EHT Relative Humidity and Temperature Sensor (5) | Decagon Devices Inc. Decagon.com | N/A | Sampling Frequency on 10 minute intervals, accuracy is ±3% between 5 and 100% relative humidity, and collect data using Em50 data loggers. For more information visit decagon.com |
| Em50 Data Logger (10) | Decagon Devices Inc. Decagon.com | 40800 | 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 |
| Sartorius Weighing Scale (1) | Sartorius Corporation | 11209-95 | Sartorius Model 11209-95, Range = 65kg, Resolution = ±1g |
| Infrared SalamandernCeramic Radiative Heater (1) | Mor Electric Heating Assoc., Inc. http://www.morelectricheating.com/ | FTE 500-240 | 5 heaters needed, adjust to ge thte right ambient/free-flow temperature |
| 2104 Temperature Control System (1) | Chromalox | 2104 | Controls the heaters |
| Infrared Temperature Sensor Regulator (1) | Exergen Corporation | N/A | Monitors the heaters temperatures |
| Stainless Steel Pitot-Static Tube (1) | Dwyer Instruments, Inc. http://www.dwyer-inst.com/ | Series 160 | 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's equation. |
| 1/2 inch Acrylic (1) | Colorado Plastics http://www.coloradoplastics.com/ | N/A | Specific heat of 1464 J kg^-1K^-1, thermal conductivity of 0.2 W m^-1K-1, and a density of 1150 kg m_-3 |
| Galvanized Steel Ducting Material (1) | Home Depot | N/A | Material used to build wind- tunnel, and both round and rectangular ducting were used in construction and connected using square-to-round reducer duct |
| Variable Speed Controller Connected to an In-Line Duct Fan (1) | Suncourt, Inc. http://www.suncourt.com/ | VS200 | 15.3 cm in Diameter Placed in-line with round duct |
| Galvanized Steel Damper (1) | Home Depot | N/A | Used to control/reduce speeds in the wind tunnel for low velocity data |
| Accusand #30/40 (1) | Unimin Corporation http://www.unimin.com/ | N/A | 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 g/cm3. |
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