AERONET DRAGON Campaign, Summer 2011
Christina Justice
College Park Scholars – Science & Global Change Program
Environmental Science and Policy
christinaj.justice@gmail.com
College Park Scholars Academic Showcase, May 4, 2012
Introduction:
Activities:
During the summer of 2011 I worked as an
intern at NASA Goddard Space Flight Center
for the AERONET calibrating the AERONET
(Aerosol Robotic Network) - a network
DRAGON campaign, deploying , of ground
based sun photometers – instruments that
measure the amount of aerosols in the
atmosphere.
During my time at AERONET I worked
on the DRAGON campaign,
implemented under the NASA funded
mission Discover AQ (Air Quality)
helping with the set up take down,
calibration and organization of the
campaign and its instruments. During this
mission I would drive out to the chosen
sites around Maryland and be involved in
the complete process of the data
collection and site analysis necessary for
the success of the campaign.
Figure 1: Aerosol Optical Thickness for NASA Goddard
site for the year 2011
Program Description:
The campaign, implemented under the NASA
funded mission Discover AQ employed NASA
aircrafts with scientific instruments on board to
collect aerosol measurements of gaseous and
particulate pollution. These measurements were
collected in a coordinated grid of 42 ground
based sun-photomers at different locations
around Maryland and the Metropolitan area.
Background
A sunphotometer is an instrument which
measures the intensity of the Sun's light when pointed
directly at the Sun. Any aerosols and gases (haze)
between the Sun and the photometer decrease the
Sun's intensity. A hazy sky would read a lower
intensity of sunlight and give a lower voltage reading
on the photometer. The automatic Sun – and skyscanning radiometers make direct Sun measurements
with a 1.2 degree full field of view every 15 minutes at
wavelengths of 340, 440, 500, 675, 870, 940, and
1020 nm.
Aerosols of different sizes respond differently at
different wavelengths. The direct measurements of
the Sun take 8 seconds to scan through all eight of
these spectral bands with a motor driven wheel
positioning each of seven filters in front of a detector
pointed at the Sun. A sequence of three
measurements is taken 30 seconds apart resulting in
3 measurements for each wavelength. These solar
measurements are then used to compute aerosol
optical thickness at each level except for the 940 nm
channel which is used to retrieve the precipitable
water. The measurements are transmitted to
communication satellites which then beam them down
to NASA GSFC. The instruments which are well
calibrated to a reference site at Mauna Loa, Hawaii,
provide a signal at each wavelength which is used to
calculate the aerosol optical thickness.
Site Information:
Location: NASA Goddard Space Flight Center,
Greenbelt Maryland 20771
Site Director: Brent Holben
Figure 2: This figure shows the
sites and flyover path for the 2011
Dragon Campaign focused on the
Maryland and metropolitan areas
Image 1: Sunphotometer at NASA Goddard
Conclusion:
The campaign ran for 6 weeks in the
middle of summer – a peak season for
aerosol production. The results and goals
of this campaign will be to better inform
policymakers on the current status of air
pollution in the tested area – aiding in
decisions and regulatory law as well as
leading to new scientific studies on the
nature of aerosols, which still remains a
largely unexplored field within
atmospheric sciences.
Future Work:
During the upcoming Summer 2012 the campaign is being expanded to
Japan and South Korea. This campaign will be measuring aerosol pollution
using the same AERONET method, enabling a comparison of data from a
dense network of daily measurements in three international Metropolitan
settings..
Acknowledgments:
I would like to thank Brent Holben and the AERONET team at
NASA GSFC for their support and mentoring on this project as well
as Drs. Holtz & Merck.