Name: measurement of aerosols optical thickness of the atmosphere using the globe handheld sun photometer
Uploaded: 2019-05-29T13:00:00
Description: Watch this Scientific Journal Video about Measurement of Aerosols Optical Thickness of the Atmosphere using the GLOBE Handheld Sun Photometer at JoVE.com

This work was supported financially by the DOD ARO grant #W911NF-15-1-0510 and National Science Foundation Research Initiation Awards under Grant No. 1411209. We express our sincere gratitude to Physics and Computer Science Department and the Division of Education at Xavier University of Louisiana.

1. Photometer Operation
NOTE: These protocols are best done by two people working together. One person holds and aligns the sun photometer while the second person record the measurements.
<ol>
	<li>Measure the longitude and latitude for the site using GPS. At the site, the first step is to activate the GPS by choosing sensor set-up from the sensor menu and select GPS. Once GPS has acquired enough satellites, latitude and longitude values will be displayed. Once values are di...

<ol>
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S., Zawadzka, O., Engelmann, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+Heat+Wave+Conditions+on+Aerosol+Optical+Properties+Derived+from+Satellite+and+Ground-Based+Remote+Sensing+over+Poland.">Effect of Heat Wave Conditions on Aerosol Optical Properties Derived from Satellite and Ground-Based Remote Sensing over Poland.</a> Remote Sensing. 9, 1199 (2017).</li><li>Brooks, D. 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D., Uchiyama, A., Asano, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+depth+measurements+of+aerosol,+cloud+and+water+vapor+using+sun+photometers+during+theFIRE+Cirrus+II.">Optical depth measurements of aerosol, cloud and water vapor using sun photometers during theFIRE Cirrus II.</a> Journal of Applied Meteorology. 35, 364-366 (1991).</li><li>A&#239;ssani, O., Mokhnache, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aerosol+size+distribution+retrieved+from+optical+depth+measurements+in+Tamanrasset+and+Blida.">Aerosol size distribution retrieved from optical depth measurements in Tamanrasset and Blida.</a> Revue des Energies Renouvelables. 15 (2), 207-218 (2012).</li><li>Bucholtz, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rayleigh-scattering+calculations+for+the+terrestrial+atmosphere.">Rayleigh-scattering calculations for the terrestrial atmosphere.</a> Applied Optics. 34, 2765-2773 (1995).</li><li>Brooks, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+Solar+Radiation+and+Its+Transmission+through+the+Atmosphere.">Monitoring Solar Radiation and Its Transmission through the Atmosphere.</a> The GLOBE Program's Aerosols, Water Vapor, and UVA Monitoring Projects. , (2006).</li><li>Holben, B. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=AERONET+-+A+federated+instrument+network+and+data+archive+for+aerosol+characterization.">AERONET - A federated instrument network and data archive for aerosol characterization.</a> Remote Sensing of the Environment. 66, 1-16 (1998).</li><li>Toledo, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=AOT+retrieval+procedure+for+distributed+measurements+with+low-cost+Sun+photometers.">AOT retrieval procedure for distributed measurements with low-cost Sun photometers.</a> Journal of Geophysical Research Atmospheres. 123, 1113-1131 (2017).</li><li>Giles, D. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advancements+in+the+Aerosol+Robotic+Network+(AERONET)+1+Version+3+Database+-+Automated+Near+Real-Time+Quality+Control+Algorithm+with+Improved+Cloud+Screening+for+Sun+Photometer+Aerosol+Optical+Depth+(AOD)+Measurements.">Advancements in the Aerosol Robotic Network (AERONET) 1 Version 3 Database - Automated Near Real-Time Quality Control Algorithm with Improved Cloud Screening for Sun Photometer Aerosol Optical Depth (AOD) Measurements.</a> Atmospheric Measurement Techniques Discussions. , (2018).</li><li>Zawadzka, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studies+of+aerosol+optical+depth+with+the+use+of+Microtops+II+sun+photometers+and+MODIS+detectors+in+coastal+areas+of+the+Baltic+Sea.">Studies of aerosol optical depth with the use of Microtops II sun photometers and MODIS detectors in coastal areas of the Baltic Sea.</a> Acta Geophysica. 62 (2), 400-422 (2014).</li><li>Bovchaliuk, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aerosol+Microtops+II+sunphotometer+observations+over+Ukraine.">Aerosol Microtops II sunphotometer observations over Ukraine.</a> Advances in Astronomy and Space Physics. 3, 46-52 (2013).</li><li>More, S., Kumar, P. 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The first step in this protocol is to define the study site. This is done by using a GPS to find the longitude and latitude of the study site. The longitude and latitude values are critical in the calculation of AOT using equation 1. During measurement, it is crucial that the sun photometer is pointed directly and firmly at the sun. The tiny hole at the top bracket of the handheld sun photometer reduces the amount of scattered light reaching the LED detectors in the sun photometer. Equation 1 is an approximation that ass...

Atmospheric aerosols are minute solid and liquid particles (ranging from submicron to millimeter size) suspended in the air. Some aerosols are produced through human activity and others are produced by natural processes1,2,3,4. Aerosols in the atmosphere reduce the amount of solar energy reaching the earth&#8217;s surface by scattering or absorbing light and thermal radiation from the sun. The amount of aerosol in the atmosphere varies significantly with location and time. There are seasonal and annual changes as well as episodic changes due to events such as large dust storms, wild fires or volcanic eruptions5,6,7,8.
The impact of aerosols on the climate and on public health are among the dominant topics in current environmental research. Aerosols affect the weather by scattering or absorbing light and thermal radiation from the sun and by acting as condensation nuclei in the formation of clouds. Aerosols also play a role in the dispersal of pathogens in the air and they can cause or enhance respiratory and cardiovascular diseases. Aerosol optical thickness (AOT) is a measure of the amount of sunlight that is absorbed or scattered by these aerosols. There are several ground-based methods for monitoring AOT9,10,11. The biggest of the ground-based AOT monitoring system is the Aerosol Robotic Network (AERONET) project. AERONET is a network of over 400 monitoring stations spread all over the world12,13. Despite this large number of monitoring stations, there are still large gaps world-wide that are not monitored for AOT. As an example, the nearest AERONET station from our study site is about 90 km away. This paper describes the use of a portable handheld sun photometer that can be used to bridge the gaps between AERONET monitoring stations. The portable handheld sun photometer is an ideal instrument for use by students around the world in a global aerosol monitoring network14,15. The Global Learning and Observations to Benefit the Environment (GLOBE) program provides a platform for such a network, through thousands of schools in all the 50 states of the United States and in nearly 120 other countries16,17. The primary idea of the GLOBE program is to use students all over the world to provide scientifically valuable measurements of environmental parameters using inexpensive equipment. With proper guidance, students and other non-specialist can form networks of handheld sun photometers to fill the gaps between the AERONET monitoring stations. The biggest advantage of the handheld sun photometer is that it can be taken to even the remotest parts of the world. AOT measurements with other small and transportable instruments have been successfully used in the past to carry out research studies in remote and hard to access areas17,18
The main goal of this study is to use the GLOBE handheld sun photometers to track the annual, daily and hourly variation of AOT at our XULA study site and compare with measurements from a nearby AERONET station. This paper presents data for a 12 months period from September 2017 to August 2018. This is the first ever AOT recorded for the XULA site. The GLOBE sun photometer measures AOT at two wavelengths, 505 nm and 625 nm. The AERONET site at Wave CIS Site 6 measures AOT at 15 different wavelengths. For our comparison we focused on these 4 wavelengths, 667 nm, 551 nm, 532 nm and 490 nm. We chose these because they are the 4 AERONET wavelengths nearest to the GLOBE sun photometer wavelengths. To make the comparison, we extrapolated AOT values at these wavelengths for XULA site.
Measurements of AOT are done every day when the weather conditions permit. Measurements that are done when there are cirrus clouds within the vicinity of the sun are excluded in the analysis. Table 1 shows the number of days in each month that we had completely clear skies. Altogether, about 47% of the data taken was excluded.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Month</td>
			<td>Sept</td>
			<td>Oct</td>
			<td>Nov</td>
			<td>Dec</td>
			<td>Jan</td>
			<td>Feb</td>
			<td>Mar</td>
			<td>Apr</td>
			<td>May</td>
			<td>Jun</td>
			<td>Jul</td>
			<td>Aug</td>
		</tr>
		<tr>
			<td>Number of Days</td>
			<td>18</td>
			<td>20</td>
			<td>16</td>
			<td>15</td>
			<td>15</td>
			<td>15</td>
			<td>16</td>
			<td>15</td>
			<td>18</td>
			<td>15</td>
			<td>15</td>
			<td>16</td>
		</tr>
	</tbody>
</table>
Table 1:&#160;AOT measurements were done 6 times a day (7:00 AM, 9 AM, 11 AM, solar noon, 3 AM, and 5 AM). The data shown on the plots are the monthly average AOT values taken at solar noon. During each measurement time; at least five values of the sunlight voltage V and the dark voltage Vdark are taken for each channel. The mean for these five measurements is taken as the average for that measurement time. The error in these measurements is calculated as the standard deviations of these five measurements. AOT values are obtained using the equation shown below16:
<img alt="Equation 1" src="/files/ftp_upload/59257/59257eq1.jpg" />
V0 is the calibration constant of the sun photometer, R is the earth-sun distance in astronomical units, Vdark is the dark voltage recorded when light is blocked from passing through the hole on the top bracket of the sun photometer, V is the sunlight voltage recorded from the sun photometer when light passes through the hole on the top bracket, aR represents the attenuation of light due to Rayleigh scattering, P and P0 are the measured and standard atmospheric pressure, respectively, and m is the relative air mass. The relative air mass is calculated from data provided by the National Oceanic and Atmospheric Administration&#160;(NOAA). Other meteorological data such as temperature, rainfall and relative humidity are also measured at the same time. Equation 1 as given above includes the contributions of optical thickness from ozone. The effect of ozone on AOT values is calculated based on tabulated values of the ozone absorption coefficient and assumptions about the ozone amount in the atmosphere19. Bucholtz20,21 has produced tabulated values of aR based on standard atmospheres. For the 505 nm channel aR &#8776; 0.13813 and for the 625 nm channel it is ~0.05793.
The data presented here represents an example of how teams of students can be organized to take long and sustained AOT measurements. In this study, two student teams used two independently calibrated GLOBE handheld sun photometers to track the annual, daily and hourly variation of the aerosol optical thickness of the atmosphere at our XULA study site. The two Globe sun photometers used in this investigation were purchased from the IESRE (Institute for Earth Science Research and Education; one had serial number RG8-989 and the other had serial number RG8-990). Before the data from the two instruments could be combined, a regression analysis was carried out to ascertain the agreement

<table>
	<tbody>
		<tr>
			<td>A Calibrated GLOBE handheld sun photometer</td>
			<td>IESRE, USA (GLOBE sun photometer) and TERNUM, UK (Calitoo sun photometer</td>
			<td></td>
			<td>The GLOBE sun photometer measures AOT at 505nm and 625nm.</td>
		</tr>
		<tr>
			<td>Barometer</td>
			<td>Forestry suppliers, USA, Cat# 43316</td>
			<td>43316</td>
			<td>The aneroid barometer must have a clear scale with a pressure range between 940 and 1060 millibars.</td>
		</tr>
		<tr>
			<td>GLOBE cloud chart</td>
			<td>Forestry Suppliers, USA Cat#33485</td>
			<td>33485</td>
			<td>A free cloud identification chart is obtained from www.globe.gov.</td>
		</tr>
		<tr>
			<td>Hygrometer</td>
			<td>Forestry suppliers, USA, Cat# 76254</td>
			<td>76245</td>
			<td>Any digital hygrometer which measures relative humidity in the range of 20-95% with an accuracy of 5% is acceptable.</td>
		</tr>
		<tr>
			<td>Labquest2 GPS</td>
			<td>Vernier, USA, Cat LABQ2</td>
			<td>LABQ2</td>
			<td>Vernier LabQuest 2 is a standalone interface used to collect sensor data with its built-in graphing and analysis application. GPS is one of its built-in sensors</td>
		</tr>
		<tr>
			<td>Taylor Orchid Thermometer</td>
			<td>Forestry Suppliers, USA Cat# 89129</td>
			<td>89129</td>
			<td></td>
		</tr>
		<tr>
			<td>Watch</td>
			<td>Forestry suppliers, USA, Cat# 39137</td>
			<td>39137</td>
			<td>The watch must be digital and capable of measuring time up to seconds.</td>
		</tr>
	</tbody>
</table>

measurement of aerosols optical thickness of the atmosphere using the globe handheld sun photometer

Here, we describe the measurement of aerosol optical thickness using the GLOBE handheld sun photometer. Aerosol optical thickness (AOT) was measured at Xavier University of Louisiana (XULA, 29.96&#176; N, 90.11&#176; W and 3 m above sea level). The measurements were done at two different wavelengths, 505 nm and 625 nm. AOT measurements were done 6 times a day (7 AM, 9 AM, 11 AM, solar noon, 3 PM and 5 PM). The data shown in this paper are the monthly average AOT values taken at solar noon. During each measurement time; at least five values of the sunlight voltage V and the dark voltage Vdark are taken for each channel. The mean for these five measurements is taken as the average for that measurement time. Other meteorological data such as temperature, surface pressure, rainfall and relative humidity are also measured at the same time. The whole protocol is completed within a time span of 10&#8211;15 min. The measured AOT values at 505 nm and 625 nm are then used to extrapolate the AOT values for wavelengths 667 nm, 551 nm, 532 nm and 490 nm. The measured and extrapolated AOT values were then compared with values from the nearest AERONET station at Wave CIS site 6 (AERONET, 28.87&#176; N, 90.48&#176; W and 33 m above sea level), which is about 96 km south of XULA. In this study we tracked the annual and daily variations of AOT for a 12 month period from September 2017 to August 2018. We also compared AOT data from two independently calibrated GLOBE handheld sun photometers at the XULA site. The data show that the two instruments are in excellent agreement.

The GLOBE sun photometer measures AOT at &#955;= 505 nm and &#955;= 625 nm. The AERONET site at Wave CIS Site 6 measures AOT at 15 different wavelengths. For our comparison we focused on these 4 wavelengths of the AERONET site: 667 nm, 551 nm, 532 nm and 490 nm. To make a comparison between the two stations, we extrapolated AOT at 667 nm, 551 nm, 532 nm and 490 nm for the XULA site. This is done using the XULA site&#8217;s Angstrom coefficients. For any given site and instrument, the opti...

Watch this Scientific Journal Video about Measurement of Aerosols Optical Thickness of the Atmosphere using the GLOBE Handheld Sun Photometer at JoVE.com

Measurement of Aerosols Optical Thickness of the Atmosphere using the GLOBE Handheld Sun Photometer

The goal of the methods presented here is to measure aerosol optical thickness of the atmosphere. The sun photometer is pointed at the sun and the largest voltage reading obtained on an in-built digital voltmeter is recorded. Atmospheric measurements such as barometric pressure and relative humidity are also performed.

Here, we describe the measurement of aerosol optical thickness using the GLOBE handheld sun photometer. Aerosol optical thickness (AOT) was measured at ...

Using this protocol we can measure the aerosol optical thickness of the atmosphere using the handheld GLOBE sun photometer with an accuracy that is acceptable to the atmospheric science community. The advantage of this technique is that it can be used by everyone from high school students to college students. The GLOBE sun photometer is robust and can be used in remote and hard-to-access areas.The aerosol optical thickness protocols are clearly outlined here and easy to follow. When taking AOT measurements it is always best to work in pairs. A visual demonstration helps to understand the technique of aligning the sun photometer with the sun.At the sight, activate the GPS by choosing sensor setup from the sensor menu and select GPS. Once the GPS has acquired enough satellites, latitude and longitude values are displayed. Then, press collect data and press save.If outside temperature is more than five degrees below room temperature, keep the sun photometer wrapped in thermal foam when not in use. When taking measurements during hot summer months, keep the sun photometer in the shade when not in use. Check if the sun photometer produces a stable voltage of about 0.03 volts indoors and between one volt and five volts when light is directed on the detector.To record the air temperature, turn the rotary switch to T and record the voltage reading on the volt meter. Multiplying the voltage reading by 100 gives the air temperature in degrees Celsius. Then, set the rotary switch to the green channel of the sun photometer with one person sitting on the chair and resting his or her arms on the table.Align the sun photometer so that the light passing through the hole on the top bracket produces a sunlight spot centered over the colored dot on the bottom bracket. Have the second person record the reading on the volt meter, making sure the sun spot is stable on the dot. If voltage reading is fluctuating, record the maximum value.Record the time within 30 seconds. To obtain the dark voltage, have the person sitting down keep the sun photometer aligned to the sun with one hand then cover the hole on the top bracket with a finger from the other hand. Have the second person record the voltage reading.Next, set the rotary switch to the red channel and repeat, recording light and dark voltages. Obtain five voltage readings for the green channel and five voltage readings for the red channel. Measure the air temperature again.Observe the clouds near the sun and use the GLOBE cloud chart to check off observed features. Visible cirrus clouds are easy to observe because of their characteristic thin wispy strands. On an apparently clear day, if the cirrus clouds are not visible but the sunlight voltage reading is less than 0.5 volts, it is recommended to infer invisible cirrus clouds.To measure the relative humidity, hold the hygrometer with an extended arm away from the body. Leave it in the air for about three minutes and then take the dry bulb reading first, followed by the wet bulb reading. Find the difference in the two readings and use the relative humidity chart to establish the relative humidity.Then, use a barometer to measure and record atmospheric pressure. Calculate the aerosol optical thickness by plugging the measured values and the constants into the AOT equation. The monthly average AOT values measured at Xavier University of Louisiana over the 12 month period indicate AOT peaks in February and May.The seasonal variation of the AOT at the Xavier University of Louisiana site categorizes December, January, and February as winter. March, April, and May as spring. June, July, and August as summer.September, October, and November as fall. Based on extrapolation, AOT for four wavelengths, 667 nanometers, 551 nanometers, 532 nanometers, and 490 nanometers, at the Xavier University of Louisiana site was compared with the data at the AERONET station. The arrows show the AOT peaks in February and in May for both sites.The reliability of the GLOBE sun photometers was checked by comparing two independently calibrated instruments against each other. The agreement between the two sun photometers is stronger for the 505 nanometer red channel than the 625 nanometer green channel. This difference is because the red LED has stronger sensitivity to temperature than the green LED.The daily variation of AOT was between 0.265 in the morning and 0.06 in the evening for the red channel which corresponds to about 77%variation. The data shows a peak at 9:00 a.m. of 0.265 and another peak at 3:00 p.m.of 0.182 for the red channel. The green channel showed similar peaks. The most important thing to remember is that these measurements do not work when the sun is obscured by cirrus clouds.The presence of cirrus clouds can result in false values for AOT. The next logical step after this is to use the Calitoo sun photometer with its blue, green, and red channels to validate the GLOBE sun photometer and use both instruments into the AERONET sites. At present there are over 400 AERONET monitoring stations around the world but even these are not enough to cover the whole planet.Our hope is that the GLOBE handheld sun photometers, using the protocols describe here, can be used to bridge the gaps left out by AERONET.

Research

JoVE Journal

Environment

Determination of Microbial Extracellular Enzyme Activity in Waters, Soils, and Sediments using High Throughput Microplate Assays

Much of the nutrient cycling and carbon  processing in natural environments occurs through the activity of extracellular  enzymes released by ...

Measurement of Greenhouse Gas Flux from Agricultural Soils Using Static Chambers

Measurement of greenhouse gas (GHG) fluxes between the soil and the atmosphere, in both managed and unmanaged ecosystems, is critical to understanding the ...

VacuSIP, an Improved InEx Method for In Situ Measurement of Particulate and Dissolved Compounds Processed by Active Suspension Feeders

VacuSIP, an Improved InEx Method for In Situ Measurement of Particulate and Dissolved Compounds Processed by Active Suspension Feeders

Benthic suspension feeders play essential roles in the functioning of marine ecosystems. By filtering large volumes of water, removing plankton and ...

Biofilm Removal Using Carbon Dioxide Aerosols without Nitrogen Purge

Biofilms can cause serious concerns in many applications. Not only can they cause economic losses, but they can also present a public health hazard. ...

Controlled-release of Chlorine Dioxide in a Perforated Packaging System to Extend the Storage Life and Improve the Safety of Grape Tomatoes

A controlled-release chlorine dioxide (ClO2) pouch was developed by sealing a slurry form of ClO2 into semipermeable polymer film; the release properties ...

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 ...

Production and Measurement of Organic Particulate Matter in the Harvard Environmental Chamber

The production and the evolution of atmospheric organic particulate matter (PM) are insufficiently understood for accurate simulations of atmospheric ...

Measurement of the Rheology of Crude Oil in Equilibrium with CO2 at Reservoir Conditions

Measurement of the Rheology of Crude Oil in Equilibrium with CO2 at Reservoir Conditions

A rheometer system to measure the rheology of crude oil in equilibrium with carbon dioxide (CO2) at high temperatures and pressures is described. The ...

Preparation of Authigenic Pyrite from Methane-bearing Sediments for In Situ Sulfur Isotope Analysis Using SIMS

Preparation of Authigenic Pyrite from Methane-bearing Sediments for In Situ Sulfur Isotope Analysis Using SIMS

Different sulfur isotope compositions of authigenic pyrite typically result from the sulfate-driven anaerobic oxidation of methane (SO4-AOM) and ...

Development of New Methods for Quantifying Fish Density Using Underwater Stereo-video Tools

The use of video camera systems in ecological studies of fish continues to gain traction as a viable, non-extractive method of measuring fish lengths and ...