f495dd6c-f61c-45c6-b627-0ba0ada0045c eng d83f95af-91e7-443e-974f-c7e1f0be700d Ev-K2-CNR +39 035 3230511 +39 035 3230551 Via San Bernardino 145 Bergamo BG 24126 Italy metadata@evk2cnr.org http://www.evk2cnr.org 2011-09-26T10:08:22 ISO 19115:2003/19139 1.0 1 WGS 1984 EPSG 7.4 Nephelometer TS INTEGRATING NEPHELOMETER total scattering coefficient 2011-04-01T19:01:00 At the Nepal Climate Observatory - Pyramid, aerosol total and back scattering coefficients at three wavelengths (450, 550 and 700 nm) are derived by an integrating nephelometer (model TSI 3563). The integrating nephelometer is a high-sensitivity device capable of measuring the scattering properties of aerosol particles. The nephelometer measures the light scattered by the aerosol and then subtracting light scattered by the walls of the measurement chamber, light scattered by the gas, and electronic noise inherent in the detectors. Aerosol light scattering coefficient, ðsp, is measured with an integrating nephelometer [see e.g, Heintzenberg and Charlson, 1996]. Integrating nephelometers have been operated at baseline monitoring stations since the deployment of a four-wavelength instrument at NOAA's Mauna Loa Observatory in 1974. At present, there are about a dozen sites monitoring ðsp routinely around the globe, many of them part of the GAW global network. This instrument operates at wavelengths of 450, 550, and 700 nm, and has the added feature of being able to measure ðsp over two angular ranges: total scattering (7-170° degrees) and hemispheric backscattering (90-170°, denoted as ðbsp). The determination of the direct effects of aerosols on the earth radiation balance requires quantitative information on the optical properties of atmospheric aerosols. Through scattering and absorption of solar radiation, aerosols can cool or warm the Earth’s atmosphere and alter the climate. Measuring the scattering variability is a try to understand how the aerosol optical properties vary with time, season and long range transport of pollutants. Ev-K2-CNR +39 035 3230511 +39 035 3230551 Via San Bernardino 145 Bergamo BG 24126 Italy evk2cnr@evk2cnr.org Paolo Bonasoni Institute of Atmospheric Sciences and Climate (ISAC) - CNR +39 051 639 9590 +39 051 639 9652 Via Gobetti 101 Bologna BO 40129 Italy p.bonasoni@isac.cnr.it Paolo Laj CNRS Laboratoire de Meteorologie Physique - Laboratoire de Glaciologie +33 685628874 +33 473405132 Avenue des Landais Aubiere Cedex 63177 France laj@lgge.obs.ujf-grenoble.fr https://geoportal.mountaingenius.org/geonetwork/srv/eng/resources.get?uuid=f495dd6c-f61c-45c6-b627-0ba0ada0045c&fname=Piramide_s.png thumbnail png https://geoportal.mountaingenius.org/geonetwork/srv/eng/resources.get?uuid=f495dd6c-f61c-45c6-b627-0ba0ada0045c&fname=Piramide.png large_thumbnail png SHARE Network Station High Altitude WMO GAW GAWSIS CEOP Nepal Himalaya aerosol aerosol total scattering coefficient air research pollution ecosystems landscape natural areas climate No conditions apply climatologyMeteorologyAtmosphere environment geoscientificInformation 80.0522 88.1946 26.3684 30.4247 https://geoportal.mountaingenius.org/webapp/srv/en/resources.get?id=106&fname=&access=private WWW:LINK-1.0-http--link SHARE Geonetwork portal http://evk2.isac.cnr.it/ WWW:LINK-1.0-http--partners ISAC EVK2-Nepal Climate Observatory - Pyramid website http://gaw.empa.ch/gawsis/reports.asp?StationID=-739518674 WWW:LINK-1.0-http--partners GAWSIS (Global Atmosphere Watch Station Information System) report about Nepal Climate Observatory - Pyramid http://www.ceop-he.org/cms/ WWW:LINK-1.0-http--partners Official website of CEOP-HE (Coordinated Energy and water cycle Observation Project - High Elevation) https://geoportal.mountaingenius.org/webapp/srv/en/resources.get?id=133&fname=3563.pdf&access=private WWW:DOWNLOAD-1.0-http--download 3563.pdf Product Information -Model 3563 Integrating Nephelometer data: aerosol total scattering coefficient TSI Integrating Nephelometers are designed specifically for studies of direct radiative forcing of the Earth’s climate by aerosol particles, or studies of ground-based or airborne atmospheric visual air quality in clean areas. They may also be used as an analytical detector for aerosol particles whenever the parameter of interest is the light-scattering coefficient of the particles after a pretreatment step, such as heating, humidification, or segregation by size. The light-scattering coefficient is a highly variable aerosol property. Integrating Nephelometers measure the angular integral of light scattering that yields the quantity called the scattering coefficient, which is used in the Beer-Lambert Law to calculate total light extinction. Model 3563 includes three-wavelength and backscatter features. During operation, a small, turbine blower draws an aerosol sample through the large diameter inlet port into the measurement volume. There, the sample is illuminated over an angle of 7 to 170 degrees by a halogen light source that has been directed through an optical pipe and opal glass diffuser. The sample volume is viewed by three photomultiplier tubes (PMTs) through a series of apertures set along the axis of the main instrument body. Aerosol scattering is viewed against the dark backdrop of a very efficient light trap. The light trap, apertures, and a highly light-absorbing coating on all internal surfaces combine to give a very low scattering signal from the walls of the instrument. The light scattered by the aerosol is split into three colors using high-pass and band-pass color filters in front of the PMT detectors. A constantly rotating reference chopper provides three modes of signal detection. The first mode, described above, is a measure of the aerosol light-scattering signal allowed by an opening in the rotating shutter. The second mode blocks all light from detection and gives a measurement of the PMT dark current, which is subtracted from the measured signal. The third mode inserts a translucent portion of the shutter into the direct path of the light to provide a measure of the light-source signal. In this way, the instrument compensates for changes in the light source. In backscatter mode, the backscatter shutter rotates in front of the light source to block light in the 7- to 90-degree range. When this portion of light is blocked, only light scattered in the backward direction is transmitted to the PMT detectors. The backscatter signal can be subtracted from the total signal to calculate forward-scattering data. When this measurement is not of interest, the backscatter shutter can be “parked” in the total-scatter position. Periodically, an automated ball-valve built into the inlet can be activated to divert all of the aerosolsample through a high-efficiency filter. This gives a measure of the clean-air signal for the local environment. This signal is subtracted, along with the PMT dark-current signal, from the aerosol-scatter signal to give only that portion of the scatter signal provided by the sample aerosol. Particle-scattering parameters for all three wavelengths of total and backscatter signal are continuously averaged and passed to a computer or data logger for permanent storage. A built-in sample heater minimizes condensation on the instrument walls caused by humid aerosols. At high humidities, atmospheric particles such as sulfates and sodium chloride adsorb water and can therefore undergo phase transitions. The result would be changes in particle size, shape, and refractive index. Operating aerosol instruments in an air-conditioned laboratory often results in sample flows with greater than 100-percent relative humidity. The heater protects against this problem by warming the walls of the sample chamber to match the temperature of the inlet air sample. The heater can be switched on or off as needed. 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