Identification

File identifier

bdee2e42-232d-4add-99f0-ec7687f2203d   XML

Hierarchy level

Series

Online resource

Protocol

WWW:LINK-1.0-http--link

Protocol

WWW:LINK-1.0-http--partners

Protocol

WWW:LINK-1.0-http--partners

Protocol

WWW:LINK-1.0-http--partners

Protocol

WWW:DOWNLOAD-1.0-http--download

Resource identifier

Encoding

Projection

code

WGS 1984

Classification of data and services

Topic category

• Climatology, meteorology, atmosphere
• Environment
• Geoscientific information

Classification of data and services

Classification of data and services

Keywords

Geographic coverage

N

S

E

W

Temporal reference

Temporal extent

Temporal extent

Date ( Publication )

2011-04-01T19:01:00

Quality and validity

Lineage

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 aerosol sample 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.

Conformity

Conformity

Conformity

Conformity

Conformity

Conformity

Restrictions on access and use

Access constraints

Restrictions on access and use

Responsible organization (s)

Contact for the resource

Organisation name

Ev-K2-CNR

Email

evk2cnr@evk2cnr.org

Organisation name

Institute of Atmospheric Sciences and Climate (ISAC) - CNR

Email

p.bonasoni@isac.cnr.it

Organisation name

CNRS Laboratoire de Meteorologie Physique - Laboratoire de Glaciologie

Email

laj@lgge.obs.ujf-grenoble.fr

Responsible organization (s)

Contact for the resource

Organisation name

Ev-K2-CNR

Email

evk2cnr@evk2cnr.org

Organisation name

Institute of Atmospheric Sciences and Climate (ISAC) - CNR

Email

p.bonasoni@isac.cnr.it

Organisation name

CNRS Laboratoire de Meteorologie Physique - Laboratoire de Glaciologie

Email

laj@lgge.obs.ujf-grenoble.fr

Metadata information

Contact for the metadata

Organisation name

Ev-K2-CNR

Email

metadata@evk2cnr.org

Date stamp

2011-09-21T10:06:24

Metadata language

eng

Character set

UTF8