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Remote Sensing of Aerosols. Zhanqing Li & R. Dickerson Dept. of Atmos. & Oceanic Science University of Maryland. What are aerosols and where are they from ?. Pollution over India The view from Tibet Sea of pollution Over India Image from the Shuttle. Aerosol Types and Origin.

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slide1

Remote Sensing of Aerosols

Zhanqing Li

& R. Dickerson

Dept. of Atmos. & Oceanic Science University of Maryland

slide3

Pollution over India

The view from Tibet

Sea of pollution Over India

Image from the Shuttle

aerosol types and origin
Aerosol Types and Origin
  • Aerosol particles larger than about 1 mm in size are produced by windblown dust and sea salt from sea spray and bursting bubbles.
  • Aerosols smaller than 1 µm are mostly formed by condensation processes such as conversion of sulfur dioxide (SO2) gas (released from volcanic eruptions) to sulfate particles and by formation of soot and smoke during burning processes.
  • After formation, the aerosols are mixed and transported by atmospheric motions and are primarily removed by cloud and precipitation processes.
slide6

Pollution/dust in China

Smoke

Pollution?

Saharan dust

Sea Salt

Pollution/dust in India

Dust and smoke are Transported to the North-East Atlantic. From MODIS

slide7

Natural biogenic aerosol particles – Wherever you have trees or vegetation, these particles are there. These are from Brazil.

P.S.: Are these particles spherical? Are they Sulfates? Soil Dust? Sea Salt?

photos from Gunther Helas, MPIC

slide8

Aerosol Size Distribution

  • It presents 3 modes :
      • - « nucleation  »: radius is between 0.002 and 0.05 mm. They result from combustion processes, photo-chemical reactions, etc.
      • - « accumulation »: radius is between 0.05 mmand 0.5 mm. Coagulation processes.
      • - « coarse »: larger than 1 mm. From mechanical processes like aeolian erosion.
  • « fine » particles (nucleation and accumulation) result from anthropogenic activities, coarse particles come from natural processes.

0.01

0.1

1.0

10.0

slide10

Aerosol Observation Programs

  • In recent years, a great deal of effort has gone into improving measurements and data sets:
  • It is feasible to shift the estimate of aerosol radiative effects fromlargely model-basedtoincreasingly measurement-based.

MISR

slide12

NASA’s AERONET

  • The AERONET (AErosol RObotic NETwork) program: a federation of ground-based remote sensing aerosol networks.
  • AERONET provides global observations of spectral aerosol optical depth (AOD), inversion products, and precipitable water.
  • Quality levels: Level 1.0 (unscreened), Level 1.5 (cloud-screened), and Level 2.0 (cloud-screened and quality-assured).
instrumentation
Instrumentation
  • The Cimel Electronique 318A spectral radiometer is a solar-powered, weather-hardy, robotically-pointed sun and sky spectral sun photometer.
  • A sensor head points the sensor head at the sun according to a preprogrammed routine.
  • The Cimel controller, batteries, and Vitel

satellite transmission equipment are usually

deployed in a weatherproof plastic case.

Cimel Spectral Radiometer

slide15

Which of the three levels would you use to have the highest confidence in your data set? Which has the most data?

Sun photometer system

spectral radiometer
Spectral Radiometer
  • The radiometer makes two basic measurements-either direct sun or sky-both within several programmed sequences.
  • The direct sun measurements are made in eight spectral bands requiring approximately 10 seconds
    • at wavelengths of 340, 380, 440, 500, 670, 870, 940 and 1020 nm
    • the 940 nm channel is used for column water abundance determination
  • A preprogrammed sequence of measurements is taken by these instruments from 7 am-7pm daily.
slide17

Sun Photometer Tutorial

http://calipsooutreach.hamptonu.edu/sunphoto-sim/photometer.html

http://aeronet.gsfc.nasa.gov/

http://aeronet.gsfc.nasa.gov/cgi-bin/type_one_station_opera_v2_new?site=GSFC&nachal=2&level=1

http://aeronet.gsfc.nasa.gov/new_web/DRAGON-USA_2013_Houston.html

slide18

On NASA AERONET site

  • Find a nearby Cimel sun photometer
  • Determine the annual average AOD and seasonal cycle
  • Look at a few individual days.
  • July 2011 was dry and hot; August 2011 was rainy. Can you see a difference?
  • Pick a polluted location and a pristine one – examine the differences.
  • Repeat for water vapor, Angstrom exp.
aerosol climatology from aeronet
Aerosol Climatology from AERONET

Cooling

Hansen et al. (1997)

Heating

Dubovik, O., B. Holben, T. F. Eck, A. Smirnov, Y. J. Kaufman, M. D. King, D. Tanré, and I. Slutsker, 2002: Variability of absorption and optical properties of key aerosol types observed in worldwide locations. J. Atmos. Sci., 59, 590–608.

256 citations

summary
Summary
  • Remote sensing with sun photometers is a powerful tool for monitoring AOD and other aerosol properties.
  • Industrial aerosols tend to be small and highly reflective in developed countries.
  • Mineral dust is larger and absorbs more radiation.
  • Biomass burning can be sootier and absorb even more radiation.
  • AERONET provides a world-wide network.
  • Only works when you can see the sun.
  • This is ok for satellite “validation”
misr provides new angle on haze
MISR Provides New Angle on Haze

September 7, 2000

Nadir

46° Forward

60° Forward

70° Forward

aerosol retrieval over the appalachians
Aerosol Retrieval over the Appalachians

September 7, 2000

Nadir

70° Forward

Aerosol optical thickness