Remote Sensing of Troposphere Ozone

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Remote Sensing of Troposphere Ozone

• Discussion Prepared by
• Drew Silverman

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Brief Outline

• Abstract
• Why Tropospheric Ozone Content is Important for
  Us
• Theory and Practicality of Sensing Ozone
• United States Findings/Results
• Future of Remote Sensing for Tropospheric Ozone
• Public Policy and Conclusions

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Abstract

• Due to the deterioration of the ozone in the
  stratosphere, the remote sensing of Ozone has
  become a popular topic in scientific journals. I
  will discuss the analysis of troposphere ozone,
  which can be harmful to humans when contacted in
  large amounts for certain period of times. I will
  investigate fully the Earth Probe TTO and
  Nimbus-7, ability to detect and diagnose lower
  atmospheric Ozone. It has been shown recently
  that Nimbus-7 has an effective resolution in
  detecting troposphere Ozone and is currently
  being researched to improve the equations used in
  modern day remote sensors. After offering an
  analysis of remote sensing equipment and it's
  effectiveness in sensing ozone, I will discuss
  the practical implications remote sensing of this
  lower troposphere phenomenon can have on human
  health.
• On a global level, troposphere Ozone can be
  sensed daily. This contributes directly to a
  constant science that needs to be monitored. I
  will discuss public policy and what changes could
  be brought about with successful sensing of this
  known pollutant. I will later discuss the future
  of Ozone detection and what may be necessary to
  improve the science itself specifically.

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Ozone Exceedance

• Defined as
• Exceedance days are defined with an 8-hour
  average ozone concentration of more than 110
  mg/m3 or 0.075 ppm (the threshold value for
  protection of human health) at ground level.
• Source EPA-ETC/AQ

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Effects of Ozone

• Short Term Exposure (lt 8 Hours to 0.085 ppm) (2)
• Coughing
• Shortness of breath
• Pain on inhalation
• Long Term Exposure (gt4 Days to 0.085 ppm) (2)
• Increased frequency of asthma attacks
• Increased use of health care services
• Death reported in the elderly due to loss of lung
  capacity
• Childhood asthma shows direct correlation to
  exposure
• Biosphere suffers due to plant destruction

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Effects of Ozone (cont)

• Ozone occur an average of 20 times yearly in New
  Jersey (1).
• Colliers Mills, NJ (lt10 miles from Jackson) saw
  32 exceedance days in 2003 (1).
• These type of days result in high summer
  respiratory problems in all ages, but
  particularly the elderly.

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What Causes Ozone?

• What Causes Buildup of Tropospheric Ozone? (2)
• Biomass Burning
• Tropopause transmission- Gradient forces cause
  a exchange of ozone between stratosphere and
  troposphere.
• Sea Breeze Circulation Daily sea breezes cause
  recycling of old ozone leading to higher
  concentrations.
• Heavy Industry Leading cause of Ozone
• Solar Heating Main catalyst in creating
  tropospheric Ozone.
• Ozone formation is considerably enhanced by
  presence of hydrocarbons and oxides of nitrogen
  in the air. Ozone is formed only with the help
  of the solar radiation. The highest
  concentrations occur generally in the afternoon
  hours.

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Problems with Sensing Tropospheric Ozone

• Unlike stratospheric ozone, lower levels are more
  sensitive to ground level changes (e.g..
  pollution, forest fires) causing small scale
  anomalies.
• Resolution of current remote sensors is usually
  poorer than 1 degree latitude by 1 degree
  longitude, this resolution would only account for
  the median ozone level in the pixel resolution.
  This would be equivalent to a measurement from
  just north of Washington D.C. to New York City.
• Measurements have also shown to be inconsistent
  at times with ground level records (3).
• Heavy clouds and weather conditions often lead to
  skewed data (3).

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Theory

• Many satellite manufactures claim there product
  can accurately this is a tough buy considering
  all the interferences that could occur.
• The principle of detection uses albedo as a ratio
  of backscattered UV back to the satellite. Ozone
  absorbs strongly in the UV region of 312-380 nm.
  Comparing what fraction of the incoming radiance
  in this band is reflected back to the passive
  sensor, it is possible to relate this value to
  the total ozone amount. To map total ozone, the
  instrument scans through the sub satellite point
  in a direction perpendicular to the orbital
  plane. According to the principles of sounding,
  the instruments can retrieve a vertical profile
  of 6 different elevations (given the current
  technology) of ozone. Data from the most
  absorbing band come primarily from the top of the
  stratosphere, whereas data from the least
  absorbing come from nearer the ground surface it
  is therefore possible to get a profile at six
  different altitudes of data.
• Although several algorithms are used to correct
  for the many possible interferences, several
  sources of uncertainty remain in the ozone
  determination. Total uncertainty has been
  estimated around 5.5, mainly due to troposphere
  ozone, retrieval errors and uncertainties in the
  ozone molecular cross section for the absorption.
  Other sources of interference, localized in space
  and time are volcanic aerosols, PST, high terrain
  and rarely, solar eclipses (1).

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Nimbus-7

• The TOMS (Total Ozone Mapping Spectrometer)
  program began with the launch of TOMS Flight
  Model 1 on the Nimbus-7 spacecraft on October
  24, 1978 (4).
• SBUV (Solar Backscatter Ultraviolet) instrument
  onboard the Nimbus 7 spacecraft alarmed
  scientists to the disintegration of the Ozone
  Layer in the arctic.
• TOMS instrument failed on May 7, 1993.

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Nimbus-7 Specs

• Designation 11080 / 78098A
• Launch date - 24 Oct 1978
• Country- United States
• Primary Mission - Meteorology
• Perigee/Apogee - 944/956 km
• Inclination - 99
• Period - 104 min
• Orbital cycle - 6 days
• Mass at launch - 827 kg (4)

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Modified Residual Method

• Nimbus-7 used the Modified Residual Method to
  determine troposphere ozone concentration (3).
• The modified residual method determines ozone
  profile information in the troposphere by
  combining measurements of cloud top pressure and
  above-cloud column ozone measurements of Nimbus 7
  Total Ozone Mapping Spectrometer (TOMS)
  above-cloud column ozone and Nimbus 7 Temperature
  Humidity Infrared Radiometer (THIR). This
  combination leads to a estimation in ground level
  ozone concentration (3).

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After Volcanic Eruption..
Source- (4)
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Ozone Concentration from Nimbus
Source- (4)
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Nimbus-7 Downfalls

• Old technology and equations led to a high error
  (gt5.5) on lower tropospheric ozone (4).
• Equipment was struck several times by space
  junk damages the lenses on the ozone sensors.
• New improved sensors (like NASAs AURA) into
  orbit after 2000 (5).

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Earth Probe TTO Specs

• Product TOMS Modified Residual (5)
• Temporal Coverage Aug 8 - Sep 29, 2000
• Spatial Coverage lat (-25 - 0), Long (-41 - 75)
  Frequency Daily 9-Day Averages
• Format Data ASCII Image GIF
• Resolution 1 deg Latitude by 2 deg Longitude

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Earth Probe TTO Cont.
Relatively Low Resolution Product...

• Relatively Low Resolution
• Poor capability in showing the flow of biomass
  burning and or significant events (Sept 11.
  attacks).
• Works well in performing basic global ozone
  patterns.
• Capable of calculating sophisticated products
  from raw Ozone Data.

Source- (4)
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Post Data Products
GIS Integrated Counties..

• The Earth Probe, while not high resolution, can
  create many level III products.
• GIS is integrated into the data base of the Earth
  Probe for use in analysis (5).

Source- (4)
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The Future

• Thermal Emission Spectroscopy- Using satellite IR
  sensors to integrate data to the TOMS sensor on
  cloudy days. Completing a full image that would
  have normally been incorrect due to lack of
  accurate ground level IR emission results (5).
• Higher Resolution- The current resolution is not
  conducive to air pollution modeling. This will
  be changed in the next 20 years. NASAs goal is
  to put into orbit a sensor that has less than ½
  degree lat/long resolution (5).
• More Level III products- More integration of air
  pollution modeling by incorporating calculations
  within the sounder (5).

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Public Policy

• Perhaps with a higher spatial resolution of our
  remote sensors, more attention will be brought to
  this particular harmful pollutant.
  Unfortunately, exceedances occur often in the
  United States, especially here in the North-East.
  
• The alarm in stratospheric ozone has taken a lot
  of the attention off what is around us here at
  the surface.
• Proposals have been rejected to lower the
  exceedance standard to 100 mg/m3 in 2006 (5).

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Sources

• Nimbus-7
• http//toms.gsfc.nasa.gov/n7toms/n7sat.html
• (2) EPA
• http//www.epa.gov/03healthtraining.com
• (3) Thermal Emission Spectroscopy
• http//tes.asu.edu/newwhatstes.html
• (4) Private Study by David Ahrens
• Article in issue 36 of Sandia Remote Sensing
  Magazine
• (5) Protecting the Ozone Layer Lessons, Models,
  and Prospects by John D. Reid

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Thank YouQuestions?