This research was funded by the U. S. Army Research Office Award W911NF-04-1-0169, the Engineering Research and Development Center (ERDC) and National Science Foundation grant EAR-1029069. In addition, this research was supported by a Summer Programs in Undergraduate Research grant from Colorado School of Mines. The authors wish to thank Ryan Tolene and Paul Schulte for their contributions.

Note: Laboratory testing is performed using a two-dimensional bench scale tank interfaced with a climate controlled wind tunnel apparatus. Both the bench scale tank and wind tunnel are instrumented with various sensor technologies. The following protocol will first discuss the construction and preparation of the soil tank, followed by a discussion of the wind tunnel and the instrumentation of both. The tank dimensions, wind tunnel dimensions, number of sensors, and sensor technology type presented can be modified to suit the needs of a specific experimental set-up. The protocol presented below was used to experimentally study the effects of wind speed on bare-soil evaporation.
1. Construction and Preparation of Porous Media Soil Tank
<ol>
	<li>Cut a large piece of 1.2 cm thick acrylic glass into five individual panes. Assemble these panes into an open-topped soil tank with internal length, width and height of 25, 9.1 and 55 cm, respectively. Acrylic glass allows processes in the subsurface to be visually observed.</li>
	<li>Draw a 5 x 5 grid that is 25 cm by 25 cm on each of the two large glass panes (length 25 cm and height 55 cm) as shown in Figure 1. Ensure that each square within the grid has an area of 25 cm2 (Figure 1). The grid will be used to properly space the sensors within the soil tank.</li>
</ol>
<img alt="Figure 1" src="/files/ftp_upload/52704/52704fig1highres.jpg" width="700" /> 
Figure 1: Schematic front and side views of the soil tank used for the experimental set-up (dimensions are in centimeters). (a) The front view of the soil tank displaying the grid system consisting of twenty-five 5 cm x 5 cm squares. (b) The side view of the soil tank, showing the installed temperature, relative humidity and soil moisture sensor network as a function of depth. Note that the schematics are not drawn to scale.
<ol start="3">
	<li>On one of the large glass planes, drill a total of twenty-five 1.9 cm (&#190; inch) diameter holes for the soil moisture sensors.
	<ol>
		<li>Drill each hole in the center of every square in the grid established in Step 1.2 so that the centers of the holes of two abutting squares are 5 cm apart; the first set of holes is 2.5 cm below the top of the tank. Use appropriately sized taps to cut threads into each of the newly created holes. The 5 cm spacing between sensors ensures that each sensor is outside of the sampling volume of the next closest sensor.</li>
	</ol>
	</li>
	<li>Similarly, drill and tap a total of twenty-five 0.635 cm (&#188; inch) diameter holes in the center of each grid box created during Step 1.2. Make sure that the center of each hole is spaced 5 cm apart with the first row of holes located 2.5 cm below the top of the soil tank. The 5 cm spacing between sensors ensures that each sensor is outside of the sampling volume of the next closest sensor.</li>
	<li>On the acrylic pane used as the bottom of the tank, drill and tap a single &#189; inch diameter hole in the middle of the pane. Glue a mesh screen (finer than the test soils to be used) over the hole on the internal side of the glass. On the external side of the bottom plane, install a 90&#176; elbow that is attached to flexible tubing with an adjustable valve. This valve and tubing is used to drain water from the tank at the termination of an experiment or as a way to install constant head devices for maintaining constant water table depths.</li>
	<li>Use marine grade glue or similar water resistant polymer adhesive to attach and seal the tank together as shown in Figure 1. Allow the adhesive to cure for one day.</li>
	<li>To raise the tank off of the ground and make room for the 90&#176; elbow (Figure 1), attach two additional pieces of 1.2 cm thick acrylic glass with length 12 cm and height 5 cm to the bottom of the tank.</li>
</ol>
2. Construction and Preparation of Climate Controlled Wind Tunnel
<ol>
	<li>Construct the 215 cm long upstream portion of the wind tunnel out of rectangular galvanized steel ducting material that has a width of 8.5 cm and a height of 26 cm. Surround the outside of the duct with polystyrene insulation.</li>
	<li>Drill a small hole in the side of the duct work near the downstream exit of the upstream portion of the wind tunnel for the insertion of a relative humidity-temperature sensor (Figure 2).</li>
</ol>
<img alt="Figure 2" src="/files/ftp_upload/52704/52704fig2highres.jpg" width="700" /> 
Figure 2: Complete experimental set-up, including tank, ductwork, sensors grid (dimensions are in centimeters). Complete experimental set up of the combined wind tunnel and soil-tank apparatus. The wind tunnel is elevated and sits flush with the surface of the soil tank. The soil tank is instrumented with a network of sensors used to measure a variety of subsurface and atmospheric variables. The grid circles represent the locations for inserting these sensors. A heating control system and an in-line duct fan are used to control temperature and wind speed, respectively. The pitot-static tube is used to measure wind speed. The entire apparatus sits on a weighting scale to obtain a mass balance during experimentation. Note that the schematic is not drawn to scale.
<ol start="3">
	<li>Install five ceramic infrared heating elements positioned in parallel within a reflector along the length of the upstream portion of the wind tunnel. Connect the infrared heating elements to a temperature control system regulated by an infrared temperature sensor.</li>
	<li>Construct the mid-section of the wind tunnel out of two 1.2 cm thick acrylic panels with a length and height of 25 cm and 26 cm respectively. Drill two 0.635 cm (&#188; inch) diameter holes in one of the mid-section panels to insert temperature and/or relative humidity-temperature sensors at the locations shown in Figure 2.
	<ol>
		<li>Secure the acrylic panels to the top of the soil tank side walls (i.e., panels with dimensions 25 cm x 55 cm) using a strong adhesive tape, ensuring that the wind tunnel and soil tank panels sit flush with one another.</li>
	</ol>
	</li>
	<li>Construct the first 50 cm of the downstream portion of the wind tunnel out of the same size rectangular ducting material described in Step 2.1. On the terminating side, reduce the rectangular ducting material to a 15.3 cm diameter round duct with length of 170 cm. Install a galvanized steel damper, used to adjust wind speeds, at the far downstream end of the round duct for aid in wind speed control.</li>
	<li>As in Step 2.2, drill one 0.635 cm diameter hole in the side of the downstream rectangular duct near the entrance for the insertion of a relative humidity-temperature sensor. Drill a second 0.635 cm diameter hole from the top of the rectangular duct along the centerline of the wind tunnel.</li>
	<li>Install an in-line duct fan in the middle of the round duct (i.e., 85 cm downstream from reduction described in Step 2.4) oriented to expel air from the downstream portion of the wind tunnel. Interface the fan with a variable speed controller for more precise control of rotational frequency and as a result wind speed.</li>
	<li>Use weldment material and adjustable shelving units to elevate and secure the wind tunnel apparatus. Ensure that the bottom of the upstream and downstream ductwork are flush with the top of the soil tank (Figure 2).</li>
</ol>
3. Installation of Sensors
<ol>
	<li>Prior to installation within the soil tank, secure each soil moisture and temperature sensor within a threaded NPT housing (1.9 cm and 0.635 cm housings, respectively) and seal with flashing sealant to prevent moisture intrusion. Do not use silicone-based sealant products as they can interfere with the electronics within some sensors. Cure the sensors for approximately one week.</li>
	<li>Prior to installation in the soil tank, calibrate the soil moisture sensors in accordance with the two point &#945;-mixing method developed by Sakaki et al.12.</li>
	<li>Wrap the threads of each NPT housing with plumbers tape prior to installation in the tank to help provide a better seal between the NPT threading and acrylic glass.</li>
	<li>Install a total of 25 soil moisture and temperature sensors each horizontally through the walls of the tank at the locations discussed in Step 1.2. Twist the sensor cables in sync with the NPT fitting/housing so as not damage the internal wiring within the cables. Do not over-torque the NPTs so as to prevent the glass from cracking. Connect the soil moisture sensors and temperature sensors to their designated data loggers.</li>
	<li>Install 3 relative humidity-temperature sensors on the soil surface at distances of 2.5, 12.5 and 21.5 cm from the leading edge of the tank. Place the sensors in good contact with the soil surface so that the relative humidity readings reflect the conditions at the soil surface rather than the surrounding air. Connect the sensors to data loggers.</li>
	<li>To obtain the requisite air temperature and relative humidity measurements in the atmosphere, install relative humidity-temperature sensors in the free flow section of the wind tunnel, using the holes drilled through the upstream and downstream sections of the wind tunnel as well as the panels.</li>
	<li>Install a pitot-static tube directly downstream of the soil tank through the 0.635 cm hole drilled in the top of the downstream wind tunnel section. Hold the pitot-static tube at a height of 13 cm from the floor of the section. Connect the pitot-static tube to a differential pressure transducer.</li>
	<li>Calibrate the differential pressure transducer. The pitot-static tube measures dynamic pressure which is defined as the difference of the stagnation and static pressures. The pressure differential is interpreted by the pressure transducer as a voltage differential.
	<ol>
		<li>Measure the voltage under no flow conditions (voltage should be approximately equal to 0) and for flow of a known dynamic pressure; this allows a linear relationship to be established between dynamic pressure and voltage. Determine wind speed by applying Bernoulli&#8217;s equation: 
		<img alt="Equation 1" fo:content-width="0.8in" src="/files/ftp_upload/52704/52704eq1.jpg" width="100" /> (1) 
		where V (m/sec) is wind speed, Pdynamic (Pa) is dynamic pressure, and &#961; (kg/m3) is the density of air.</li>
		<li>Compare the velocity calculated using Equation (1) with another measurement device. Here, compare the pitot-static tube differential pressure transducer with Laser Doppler Velocimetry (LDV) measurements which has an accuracy of &#177; 0.01 m/sec. 
		Note: A summary of sensors employed and their associated sampling frequencies can be found in Table 1. For sensor specifications and other information, refer to the enclosed materials/equipment list.</li>
	</ol>
	</li>
</ol>
<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Sensor</td>
			<td>Sensor Measurements</td>
			<td>Number of Sensors Employed in Experimental Apparatus</td>
			<td>Sensor Sampling Frequency (min)</td>
		</tr>
		<tr>
			<td>EC-5</td>
			<td>Soil moisture</td>
			<td>25</td>
			<td>10</td>
		</tr>
		<tr>
			<td>ECT</td>
			<td>Soil/air temperature</td>
			<td>25</td>
			<td>10</td>
		</tr>
		<tr>
			<td>SH-1</td>
			<td>Thermal properties</td>
			<td>1</td>
			<td>10</td>
		</tr>
		<tr>
			<td>EHT</td>
			<td>Relative humidity/temperature</td>
			<td>5</td>
			<td>10</td>
		</tr>
		<tr>
			<td>Infrared camera</td>
			<td>Surface temperature/evaporation</td>
			<td>1</td>
			<td>1</td>
		</tr>
		<tr>
			<td>Digital camera</td>
			<td>Visualization of drying front</td>
			<td>1</td>
			<td>60</td>
		</tr>
		<tr>
			<td>Pitot static tube</td>
			<td>Wind velocity</td>
			<td>1</td>
			<td>10</td>
		</tr>
		<tr>
			<td>Weighting scale</td>
			<td>Cumulative evaporation/evaporation rate</td>
			<td>1</td>
			<td>10</td>
		</tr>
	</tbody>
</table>
Table 1: Summary of sensors used in experimental portion of present study.
4. Pack the Soil Tank and Prepare for the Start of the Experiment
<ol>
	<li>Prior to packing the tank with soil, test its integrity by performing a leak test. Fill the tank with water and wait for 4-6 hr to ensure that no leaks in the structure or sensors have developed.
	<ol>
		<li>If leaks develop, drain the tank, let it dry overnight and fix the leaks using the same marine adhesive used during original construction. If no leaks develop, drain the soil tank and prepare for the steps below.</li>
	</ol>
	</li>
	<li>Determine the total volume of the tank with sensors in place. Carefully fill the tank with water using a graduated cylinder, making sure to record the amount of water added. Convert the recorded total volume to cubic centimeters for use in Step 4.5.</li>
	<li>Obtain dry soil to pack the soil tank. Characterize the hydraulic and thermal properties of the selected soil separately in accordance with the methods discussed in Smits et al.11</li>
	<li>Carefully wet-pack the soil tank using soil and deionized water.
	<ol>
		<li>To wet-pack the soil tank, first pour approximately 5 cm of water into the tank. Slowly add dry soil to the water in the tank, using a scoop, in 2.5 cm depth increments. Record the weight of the sand added during each lift so the porosity of the soil packing can be calculated.</li>
		<li>Upon completion of each layer, repeatedly tap the tank walls using a rubber mallet, 100-200 times, to obtain a uniform bulk density throughout. While tapping, avoid contact with the sensors and sensor wires. The use of vibratory devices should be avoided so as not to damage the network of sensitive sensors.</li>
	</ol>
	</li>
	<li>Upon completion of packing the tank, sum together the weights of each soil layer (see Step 4.4) to get the total mass of soil. Divide the total mass by the bulk density of soil (e.g. the bulk density of quartz sand is 2.65 g/cm3) to determine the volume of the sand (Vs, cm3). Calculate the porosity (&#951;, m3/m3) of the soil in the tank according to: 
	<img alt="Equation 2" fo:content-width="0.8in" src="/files/ftp_upload/52704/52704eq2.jpg" width="100" /> (2) 
	where (VT, m3) is the total volume of the empty tank determined in Step 4.2.</li>
	<li>Once the tank is fully packed, place a plastic cover such as saran wrap over the tank until the experiment is ready to start to prevent the onset of evaporation.</li>
	<li>Place the tank on a weighting scale to monitor cumulative water loss which can in turn be used to calculate evaporation rate.</li>
	<li>Calculate the hourly evaporation rate by dividing the hourly weight loss by the product of the density of water and the cross sectional area of the evaporating surface.</li>
</ol>
5. Start the Experiment and Begin Data Collection
<ol>
	<li>Once the set-up is complete, determine the desired atmospheric conditions (i.e. temperature, wind speed). Ensure that the data loggers and other data acquisition systems are turned on and set to the correct sampling intervals (e.g., every 10 min).</li>
	<li>Start the fan and temperature control system. Allow the climate conditions to equilibrate before removing the plastic cover on the surface of the soil tank. Run the experiment for the desired length of time (e.g., 15 days).</li>
</ol>

<ol>
	<li>Verstraete, M. M., Schwartz, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Desertification+and+global+change.">Desertification and global change.</a> Vegetatio. 91, 3-13 (1991).</li><li>Warren, A., Adams, W. M., Goudie, A. S., Orme, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Desertification.">Desertification.</a> The Physical Geography of Africa. , 342-355 (1996).</li><li>Katata, G., Nagai, H., Ueda, H., Agam, N., Berliner, P. 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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>

The authors declare that they have no competing financial interests.

The purpose of this protocol was to develop an experimental apparatus and associated procedures for the generation of high spatial and temporal resolution data required for studying land-atmospheric interactions with respect to heat and mass transfer processes. The experimental apparatus described consisted of a soil tank and a small wind tunnel, both of which were outfitted with an array of sensors for the measurement of pertinent soil and atmospheric variables (e.g., wind speed, relative humidity, soil and air...

Understanding the interaction between the land and atmosphere is paramount to our understanding of many current world problems such as leaking of geologically-sequestered carbon dioxide in soil, climate change, water and food supply, the accurate detection of landmines, and the remediation of ground water and soil. In addition, the primary exchanges of heat and water that drive global and regional meteorological conditions occur at the Earth&#8217;s surface. Many weather and climate phenomena (e.g., hurricanes, El Ni&#38;#241;o, droughts, etc.) are principally driven by processes associated with atmospheric-land surface interactions1. As more than half of the land surface on the Earth is arid or semiarid2-4, accurately describing the water cycle in these regions on the basis of heat and water exchanges between the atmospheric air and the soil surface is critical to improving our understanding of the aforementioned issues, particularly in regions vulnerable to extended drought and desertification. However, despite decades of research, there still remain many knowledge gaps in the current understanding of how the shallow subsurface and atmosphere interact5.
Transport processes involving liquid water, water vapor, and heat in soil are dynamic and strongly coupled with respect to interactions with the soil and enforced boundary conditions (i.e., temperature, relative humidity, thermal radiation). Numerical heat and mass transfer models commonly oversimplify or overlook a number of these complexities due in part to a lack of testing and refinement of existing theories resulting from a paucity of high temporal and spatial resolution data. Datasets developed for model validation are oftentimes lacking critical atmospheric or subsurface information to properly test the theories, resulting in numerical models that do not properly account for important processes or depend on the use of poorly understood parameters that are adjusted or fitted in the model. This approach is widely used due to its simplicity and ease of use and has in some applications shown much merit. However, this approach can be improved upon by better understanding the physics behind these &#8220;lumped parameterizations&#8221; by performing well controlled experiments under transient conditions that are capable of testing heat and water transfer theory6.
Careful experimentation in the laboratory allows precision datasets to be generated that can subsequently be used to validate numerical models. Data available from field sites are often incomplete and costly to obtain, and the degree of control needed to obtain a fundamental understanding of processes and to generate data for model validation could be considered inadequate in some cases. Laboratory experimentation of natural phenomena such as soil evaporation allows atmospheric conditions (i.e., temperature, relative humidity, wind speed) and soil conditions (i.e., soil type, porosity, packing configuration) to be carefully controlled. Many laboratory techniques used to study soil evaporation and soil thermal and hydraulic properties use destructive sampling7-10. Destructive sampling methods require that a soil sample be unpacked to obtain point data, preventing the measurement of transient behavior and disrupting soil physical properties; this approach introduces error and uncertainty to the data. Nondestructive measurements, like the method presented here, allow for more accurate determination and study of the interdependency of soil properties and processes11.
The goal of this work is to develop a soil tank apparatus and associated protocol for the generation of high spatial and temporal resolution data pertaining to the effects of changes in atmospheric and subsurface conditions on bare-soil evaporation. For this work, a small wind tunnel capable of maintaining a constant wind speed and temperature is interfaced with a soil tank apparatus. The wind tunnel and soil tank are instrumented with a suite of state of the art sensor technologies for autonomous and continuous data collection. Wind speed is measured using a stainless steel pitot-static tube attached to a pressure transducer. Temperature and relative humidity are monitored in the atmosphere using two types of sensors. Relative humidity and temperature are also monitored at the soil surface. Sensors in the subsurface measure soil moisture and temperature. Weight measurements of the tank apparatus are used to determine evaporation through a water mass balance. To demonstrate the applicability of this experimental apparatus and protocol, we present an example of bare-soil evaporation under varying wind speed conditions. The soil tank, packed homogeneously with a well characterized sand, was initially fully saturated and allowed to evaporate freely under carefully controlled atmospheric conditions (i.e. temperature, wind speed).

<table border="0" cellpadding="0" cellspacing="0">
	<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 &#177;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 minute intervals, accuracy is &#177;0.5&#176;C, Measure within a temperature of 5 and 40&#176;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 minute intervals, accuracy is &#177;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 = 65kg, Resolution = &#177;1g</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 ge thte 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</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>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&#39;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 1464 J kg^-1K^-1, thermal conductivity of 0.2 W m^-1K-1, and a density of 1150 kg m_-3</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 g/cm3.</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.

The objective of the experiment presented here was to study the effect of wind speed on evaporation from bare soil. Key properties of the test soil used in the present study are summarized in Table 2. A series of experiments were performed in which different boundary conditions at the soil surface (i.e., wind speed and temperature) were applied (Table 3). Although four experiments at different wind speeds and temperatures were performed, the majority of experimental results pres...

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

A protocol for the design and construction of a soil tank interfaced to a small climate controlled wind tunnel to study the effects of atmospheric forcings on evaporation is presented. Both the soil tank and wind tunnel are instrumented with sensor technologies for the continuous in situ measurement of environmental conditions.

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

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JoVE Journal

Environment

8.6K Views.  Colorado School of Mines. A protocol for the design and construction of a soil tank interfaced to a small climate controlled wind tunnel to study the effects of atmospheric forcings on evaporation is presented. Both the soil tank and wind tunnel are instrumented with sensor technologies for the continuous in situ measurement of environmental conditions.

Video: 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.

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

Laboratory Simulation of an Iron(II)-rich Precambrian Marine Upwelling System to Explore the Growth of Photosynthetic Bacteria

A conventional concept for the deposition of some Precambrian Banded Iron Formations (BIF) proceeds on the assumption that ferrous iron [Fe(II)] upwelling from hydrothermal sources in the Precambrian ocean was oxidized by molecular oxygen [O2] produced by cyanobacteria. The oldest BIFs, deposited prior to the Great Oxidation Event (GOE) at about 2.4 billion years (Gy) ago, could have formed by direct oxidation of Fe(II) by anoxygenic photoferrotrophs under anoxic conditions. As a method for testing the geochemical and mineralogical patterns that develop under different biological scenarios, we designed a 40 cm long vertical flow-through column to simulate an anoxic Fe(II)-rich marine upwelling system representative of an ancient ocean on a lab scale. The cylinder was packed with a porous glass bead matrix to stabilize the geochemical gradients, and liquid samples for iron quantification could be taken throughout the water column. Dissolved oxygen was detected non-invasively via optodes from the outside. Results from biotic experiments that involved upwelling fluxes of Fe(II) from the bottom, a distinct light gradient from top, and cyanobacteria present in the water column, show clear evidence for the formation of Fe(III) mineral precipitates and development of a chemocline between Fe(II) and O2. This column allows us to test hypotheses for the formation of the BIFs by culturing cyanobacteria (and in the future photoferrotrophs) under simulated marine Precambrian conditions. Furthermore we hypothesize that our column concept allows for the simulation of various chemical and physical environments &#8212; including shallow marine or lacustrine sediments.

Laboratory Simulation of an IronII-rich Precambrian Marine Upwelling System to Explore the Growth of Photosynthetic Bacteria

We simulated a Precambrian ferruginous marine upwelling system in a lab-scale vertical flow-through column. The goal was to understand how geochemical profiles of O2 and Fe(II) evolve as cyanobacteria produce O2. The results show the establishment of a chemocline due to Fe(II) oxidation by photosynthetically produced O2.

A conventional concept for the deposition of some Precambrian Banded Iron Formations (BIF) proceeds on the assumption that ferrous iron [Fe(II)] upwelling ...

Extraction and Characterization of Surfactants from Atmospheric Aerosols

Surface-active compounds, or surfactants, present in atmospheric aerosols are expected to play important roles in the formation of liquid water clouds in the Earth&#39;s atmosphere, a central process in meteorology, hydrology, and for the climate system. But because specific extraction and characterization of these compounds have been lacking for decades, very little is known on their identity, properties, mode of action and origins, thus preventing the full understanding of cloud formation and its potential links with the Earth&#39;s ecosystems.
In this paper we present recently developed methods for 1) the targeted extraction of all the surfactants from atmospheric aerosol samples and for the determination of 2) their absolute concentrations in the aerosol phase and 3) their static surface tension curves in water, including their Critical Micelle Concentration (CMC). These methods have been validated with 9 references surfactants, including anionic, cationic and non-ionic ones. Examples of results are presented for surfactants found in fine aerosol particles (diameter &#60;1 &#956;m) collected at a coastal site in Croatia and suggestions for future improvements and other characterizations than those presented are discussed.

Methods are presented for the targeted extraction of surfactants present in atmospheric aerosols and the determination of their absolute concentrations and surface tension curves in water, including their Critical Micelle Concentration (CMC).

Surface-active compounds, or surfactants, present in atmospheric aerosols are expected to play important roles in the formation of liquid water clouds in ...

Data Processing Methods for 3D Seismic Imaging of Subsurface Volcanoes: Applications to the Tarim Flood Basalt

The morphology and structure of plumbing systems can provide key information on the eruption rate and style of basalt lava fields. The most powerful way to study subsurface geo-bodies is to use industrial 3D&#160;reflection seismological imaging. However, strategies to image subsurface volcanoes are very different from that of oil and gas reservoirs. In this study, we process seismic data cubes from the Northern Tarim Basin, China, to illustrate how to visualize sills through opacity rendering techniques and how to image the conduits by time-slicing. In the first case, we isolated probes by the seismic horizons marking the contacts between sills and encasing strata, applying opacity rendering techniques to extract sills from the seismic cube. The resulting detailed sill morphology shows that the flow direction is from the dome center to the rim. In the second seismic cube, we use time-slices to image the conduits, which corresponds to marked discontinuities within the encasing rocks. A set of time-slices obtained at different depths show that the Tarim flood basalts erupted from central volcanoes, fed by separate pipe-like conduits.

Three-dimensional (3D) reflection seismology is a powerful method for imaging subsurface volcanoes. By using industrial 3D seismological data from the Tarim Basin, we illustrate how to extract the sills and the conduits of subsurface volcanoes from seismic data cubes.

The morphology and structure of plumbing systems can provide key information on the eruption rate and style of basalt lava fields. The most powerful way ...

Experimental Methods of Dust Charging and Mobilization on Surfaces with Exposure to Ultraviolet Radiation or Plasmas

Electrostatic dust transport has been hypothesized to explain a number of observations of unusual planetary phenomena. Here, it is demonstrated using three recently developed experiments in which dust particles are exposed to thermal plasma with beam electrons, beam electrons only, or ultraviolet (UV) radiation only. The UV light source has a narrow bandwidth in wavelength centered at 172 nm. The beam electrons with the energy of 120 eV are created with a negatively biased hot filament. When the vacuum chamber is filled with the argon gas, a thermal plasma is created in addition to the electron beam. Insulating dust particles of a few tens of microns in diameter are used in the experiments. Dust particles are recorded to be lofted to a height up to a few centimeters with a launch speed up to 1 m/s. These experiments demonstrate that photo and/or secondary electron emission from a dusty surface changes the charging mechanism of dust particles. According to the recently developed &#34;patched charge model&#34;, the emitted electrons can be re-absorbed inside microcavities between neighboring dust particles below the surface, causing the accumulation of enhanced negative charges on the surrounding dust particles. The repulsive forces between these negatively charged particles may be large enough to mobilize and lift them off the surface. These experiments present the advanced understanding of dust charging and transport on dusty surfaces, and laid a foundation for future investigations of its role in the surface evolution of airless planetary bodies.

Dust charging and mobilization is demonstrated in three experiments with exposure to thermal plasma with beam electrons, beam electrons only, or ultraviolet (UV) radiation only. These experiments present the advanced understanding of electrostatic dust transport and its role in shaping the surfaces of airless planetary bodies.

Electrostatic dust transport has been hypothesized to explain a number of observations of unusual planetary phenomena. Here, it is demonstrated using ...

Determination of the Settling Rate of Clay/Cyanobacterial Floccules

The mechanisms underpinning the deposition of fine-grained, organic-rich sediments are still largely debated. Specifically, the impact of the interaction of clay particles with reactive, planktonic cyanobacterial cells to the sedimentary record is under studied. This interaction is a potentially major contributor to shale depositional models. Within a lab setting, the flocculation and sedimentation rates of these materials can be examined and measured in a controlled environment. Here, we detail a protocol for measuring the sedimentation rate of cyanobacterial/clay mixtures. This methodology is demonstrated through the description of two sample experiments: the first uses kaolin (a dehydrated form of kaolinite) and Synechococcus sp. PCC 7002 (a marine coccoid cyanobacteria), and the second uses kaolin and Synechocystis sp. PCC 6803 (a freshwater coccoid cyanobacteria). Cyanobacterial cultures are mixed with varying amounts of clay within a specially designed tank apparatus optimized to allow continuous, real-time video and photographic recording. The sampling procedures are detailed as well as a post-collection protocol for precise measurement of chlorophyll a from which the concentration of cyanobacterial cells remaining in suspension can be determined. Through experimental replication, a profile is constructed that displays sedimentation rate.

The interaction and sedimentation of the clay and bacterial cells within the marine realm, observed in natural environments, can be best investigated in a controlled lab environment. Here, we describe a detailed protocol, which outlines a novel method for measuring the sedimentation rate of clay and cyanobacterial floccules.

The mechanisms underpinning the deposition of fine-grained, organic-rich sediments are still largely debated. Specifically, the impact of the interaction ...

In Situ Hybridization Techniques for Paraffin-Embedded Adult Coral Samples

Corals are important ocean invertebrates that are critical for overall ocean health as well as human health. However, due to human impacts such as rising ocean temperatures and ocean acidification, corals are increasingly under threat. To tackle these challenges, advances in cell and molecular biology have proven to be crucial for diagnosing the health of corals. Modifying some of the techniques commonly used in human medicine could greatly improve researchers&#39; ability to treat and save corals. To address this, a protocol for in situ hybridization used primarily in human medicine and evolutionary developmental biology has been adapted for use in adult corals under stress.
The purpose of this method is to visualize the spatial expression of an RNA probe in adult coral tissue that has been embedded in paraffin and sectioned onto glass slides. This method focuses on removal of the paraffin and rehydration of the sample, pretreatment of the sample to ensure permeability of the sample, pre-hybridization incubation, hybridization of the RNA probe, and visualization of the RNA probe. This is a powerful method when using non-model organisms to discover where specific genes are expressed, and the protocol can be easily adapted for other non-model organisms. However, the method is limited in that it is primarily qualitative, because expression intensity can vary depending on the amount of time used during the visualization step and the concentration of the probe. Furthermore, patience is required, as this protocol can take up to 5 days (and in many cases, longer) depending on the probe being used. Finally, non-specific background staining is common, but this limitation can be overcome.

In Situ Hybridization Techniques for Paraffin-Embedded Adult Coral Samples

The goal of this protocol is to perform in situ hybridization on adult coral samples that have been embedded in paraffin and sectioned onto glass slides. This is a qualitative method used to visualize the spatial expression of an RNA anti-sense probe in paraffin-embedded tissues.

Corals are important ocean invertebrates that are critical for overall ocean health as well as human health. However, due to human impacts such as rising ...

Sampling, Sorting, and Characterizing Microplastics in Aquatic Environments with High Suspended Sediment Loads and Large Floating Debris

The ubiquitous presence of plastic debris in the ocean is widely recognized by the public, scientific communities, and government agencies. However, only recently have microplastics in freshwater systems, such as rivers and lakes, been quantified. Microplastic sampling at the surface usually consists of deploying drift nets behind either a stationary or moving boat, which limits the sampling to environments with low levels of suspended sediments and floating or submerged debris. Previous studies that employed drift nets to collect microplastic debris typically used nets with &#8805;300 &#181;m mesh size, allowing plastic debris (particles and fibers) below this size to pass through the net and elude quantification. The protocol detailed here enables: 1) sample collection in environments with high suspended loads and floating or submerged debris and 2) the capture and quantification of microplastic particles and fibers &lt;300 &#181;m. Water samples were collected using a peristaltic pump in low-density polyethylene (PE) containers to be stored before filtering and analysis in the lab. Filtration was done with a custom-made microplastic filtration device containing detachable union joints that housed nylon mesh sieves and mixed cellulose ester membrane filters. Mesh sieves and membrane filters were examined with a stereomicroscope to quantify and separate microplastic particulates and fibers. These materials were then examined using a micro-attenuated total reflectance Fourier transform infrared spectrometer (micro ATR-FTIR) to determine microplastic polymer type. Recovery was measured by spiking samples using blue PE particulates and green nylon fibers; percent recovery was determined to be 100% for particulates and 92% for fibers. This protocol will guide similar studies on microplastics in high velocity rivers with high concentrations of sediment. With simple modifications to the peristaltic pump and filtration device, users can collect and analyze various sample volumes and particulate sizes.

Most microplastic research to date has occurred in marine systems where suspended solid levels are relatively low. Focus is now shifting to freshwater systems, which may feature high sediment loads and floating debris. This protocol addresses collecting and analyzing microplastic samples from aquatic environments that contain high suspended solid loads.

The ubiquitous presence of plastic debris in the ocean is widely recognized by the public, scientific communities, and government agencies. However, only ...

Design and Use of an Apparatus for Quantifying Bivalve Suspension Feeding at Sea

As shellfish aquaculture moves from coastal embayments and estuaries to offshore locations, the need to quantify ecosystem interactions of farmed bivalves (i.e., mussels, oysters, and clams) presents new challenges. Quantitative data on the feeding behavior of suspension-feeding mollusks is necessary to determine important ecosystem interactions of offshore shellfish farms, including their carrying capacity, the competition with the zooplankton community, the availability of trophic resources at different depths, and the deposition to the benthos. The biodeposition method is used to quantify feeding variables in suspension-feeding bivalves in a natural setting and represents a more realistic proxy than laboratory experiments. This method, however, relies upon a stable platform to satisfy the requirements that water flow rates supplied to the shellfish remain constant and the bivalves are undisturbed. A flow-through device and process for using the biodeposition method to quantify the feeding of bivalve mollusks were modified from a land-based format for shipboard use by building a two-dimensional gimbal table around the device. Planimeter data reveal a minimal pitch and yaw of the chambers containing the test shellfish despite boat motion, the flow rates within the chambers remain constant, and operators are able to collect the biodeposits (feces and pseudofeces) with sufficient consistency to obtain accurate measurements of the bivalve clearance, filtration, selection, ingestion, rejection, and absorption at offshore shellfish aquaculture sites.

A flow-through device for using the biodeposition method to quantify filtration and feeding behavior of bivalve mollusks was modified for shipboard use. A two-dimensional gimbal table built around the device isolates the apparatus from boat motion, thereby allowing the accurate quantification of bivalve filtration variables at offshore shellfish aquaculture sites.

As shellfish aquaculture moves from coastal embayments and estuaries to offshore locations, the need to quantify ecosystem interactions of farmed bivalves ...

An Experimental Protocol for Studying Mineral Effects on Organic Hydrothermal Transformations

Organic-mineral interactions are widely occurring in hydrothermal environments, such as hot springs, geysers on land, and the hydrothermal vents in the deep ocean. Roles of minerals are critical in many hydrothermal organic geochemical processes. Traditional hydrothermal methodology, which includes using reactors made of gold, titanium, platinum, or stainless-steel, is usually associated with the high cost or undesired metal catalytic effects. Recently, there is a growing tendency for using the cost-effective and inert quartz or fused silica glass tubes in hydrothermal experiments. Here, we provide a protocol for carrying out organic-mineral hydrothermal experiments in silica tubes, and we describe the essential steps in the sample preparation, experimental setup, products separation, and quantitative analysis. We also demonstrate an experiment using a model organic compound, nitrobenzene, to show the effect of an iron-containing mineral, magnetite, on its degradation under a specific hydrothermal condition. This technique can be applied to study complex organic-mineral hydrothermal interactions in a relatively simple laboratory system.

Earth-abundant minerals play important roles in the natural hydrothermal systems. Here, we describe a reliable and cost-effective method for the experimental investigation of organic-mineral interactions under hydrothermal conditions.

Organic-mineral interactions are widely occurring in hydrothermal environments, such as hot springs, geysers on land, and the hydrothermal vents in the ...