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NASA Studies High Springtime Ozone Levels Over Canada and the Arctic
This page contains archived content and is no longer being updated. At the time of publication, it represented the best available science. However, more recent observations and studies may have rendered some content obsolete.
Atmospheric scientists made seven flights to high latitudes from
Broomfield, Colorado, with bases in Churchill, Canada, and Thule,
Greenland, during the Tropospheric Ozone Production about the Spring
Equinox (TOPSE) field experiment. Remote lidar (laser radar)
measurements taken by the NASA Langley Research Center’s Lidar
Applications Group found high springtime ozone levels in the lower
atmosphere along the aircraft’s flight path. The image, recently created
to better visualize ozone data from TOPSE, is a representation of all
ozone data during April 2000. Blue areas show regions of the atmosphere
with little ozone. Yellow to red areas indicate high ozone levels, and
black areas represent the stratosphere, where ozone is very high. The
colored lines are calculated paths the air mass took going back 10 days
in time. Blue and green trajectories show air masses coming from
polluted regions of Asia and are associated with high ozone levels in
the lower atmosphere.
Background levels of ozone exist in the lower atmosphere
(troposphere) at all times, but a peak occurs during the springtime at
high northern latitudes. The timing of the peak is unusual because other
areas in the Northern Hemisphere, such as over most of the United
States, experience their highest seasonal ozone levels during the
Springtime ozone levels in the high northern latitudes in the lower
atmosphere have been increasing with time, and TOPSE scientists wanted
to know the reason for the ozone peak. They determined that higher
springtime ozone amounts could not be explained only by an increase in
the natural transport process called stratosphere-troposphere exchange.
This process mixes ozone-rich air from the upper atmosphere or
stratosphere into the lower atmosphere.
Instead scientists concluded that long-range transport moved air
pollution into remote Arctic areas during the winter and into the
spring, causing the production of the highest seasonal ozone levels over
Canada and the Arctic. Photochemical processes convert some of the air
pollution into ozone in the troposphere during the spring when more
sunlight reaches the Arctic. These processes begin when sunlight comes
into contact with chemically active molecules in the lower atmosphere
like those found in air pollution.
This research stems from an investigation that was one of many
studies conducted from February to May 2000 during TOPSE, a field
experiment funded by the National Science Foundation and led by the
National Center for Atmospheric Research (NCAR). The Lidar Applications
Group will participate in their next field campaign from January to
February 2003 in the SAGE III Ozone Loss and Validation Experiment