slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Outline PowerPoint Presentation
Download Presentation
Outline

Loading in 2 Seconds...

play fullscreen
1 / 26

Outline - PowerPoint PPT Presentation


  • 154 Views
  • Uploaded on

Outline. Introduction Instruments designed and fabricated at the Desert Research Institute, Reno Emphasis on the Integrating Nephelometer for scattering measurements Compare with Radiance nephelometer during a field study at Ft. Bliss, Texas Summary.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Outline' - iorwen


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
outline
Outline

Introduction

Instruments designed and fabricated at the Desert Research Institute, Reno

Emphasis on the Integrating Nephelometer for scattering measurements

Compare with Radiance nephelometer during a field study at Ft. Bliss, Texas

Summary

a tmospheric a erosol a pplications and r esearch
Atmospheric Aerosol Applications and Research
  • Radiation transfer, light scattering and absorption, emission.
    • Climate simulation
    • Visibility at the National Parks
    • Military applications - sensor performance and plume visibility
    • Cloud albedo (Twomey effect, more aerosol, more competition for water vapor, smaller droplets, ammonium sulfate aerosol)
    • Cloud lifetime (Black carbon causes local heating from sunlight absorption, cloud dissipation).
  • Health effects
    • PM 2.5 levels are legislated
    • Likely that PM will be further differentiated into E.C., O.C., etc.
  • Source Level Combustion
    • Engine performance
    • Power plants
why is light extinction measurement important
Why is light extinction measurement important?
  • Aerosol Radiative Transfer and Climate impacts
  • Optical Remote Sensing
  • Atmospheric Visibility
visibility good for tourism bad for military when engine plumes become visible
Visibility: Good for tourism, bad for military when engine plumes become visible.
  • IMPROVE: (Interagency Monitoring of PROtected Visual Environments)
  • Aerosols are a dominant influence on man-made visibility impairment.
  • Aerosol optical properties are very important and are measured.

National Park Service, Forest Service, Fish and Wildlife Service, Bureau of Land Management, and Environmental Protection Agency

dri instruments for light extinction measurements
DRI Instruments for light Extinction Measurements
  • Photoacoustic absorption instrument
  • Integrating-Sphere scattering instrument
  • Cavity Ring-Down (CRD) total extinction instrument
sketch of the photoacoustic instrument
Sketch of the Photoacoustic Instrument
  • Basic principles:
  • Laser light is power modulated by the chopper.
  • Light absorbing aerosols convert light to heat - a sound wave is produced.
  • Microphone signal is a measure of the light absorption.
  • Light scattering aerosols don't generate heat.
aerosol optical properties absorbing particles
Aerosol Optical Properties: Absorbing particles.

For small optical depths,

and D < 0.1 µm:

I(L)/I(0) = e(-L L),

L(1/m) ≈ S.O.C (m2/g) x r (g/m3),

L = path length,

r = aerosol concentration by mass.

Absorption dominates for D < 0.1 µm (Rayleigh scattering).

Aside: For non-absorbing aerosols, Extinction=Scattering. Note the strong dependence of the scattering coefficient on diameter!

dri crd extinction instrument
DRI CRD Extinction Instrument
  • A path length of approximately 10 km due to high reflecting mirrors
  • measures total light extinction
nephelometers measure light scattering
Nephelometers Measure Light Scattering

These instruments operate by illuminating a fixed sample volume from the side, and observing the amount of light that is scattered by particles and gas molecules in the direction of a photomultiplier tubes. The instruments integrate over scattering angles of 7-170°

radiance neph at ft bliss tx
Radiance neph at Ft. Bliss, TX

Forward angle truncation of 7 deg.

DRI neph. Signal over 4 times compared to radiance

Dust particles as big as 20 m from the road

dri nephelometer at ft bliss tx1
DRI Nephelometer at Ft. Bliss, TX

20 s time averages

Radiance forward angle trunc. of 7 deg.

DRI neph. has < 1 deg.

DRI neph. Signal over 4 times compared to radiance

Dust particles as big as 20 m from the road

summary
Summary

The integrating Nephelometer developed at the DRI provides considerable improvements for scattering measurements over the existing instruments

Further evaluation of the nephelometer undergoing currently at the Reno Aerosol Optics Experiment

A closure experiment ensures reliable measurements from the instruments