- Spreading Contrail Examples.
- New Contrail Studies.
- Search for contrails in satellite imagery.
- Clouds and Contrails in Motion.
- Link to a radio talk show where Dr. Minnis provides answers to questions about contrails and "chemtrails." It was recorded on March 19, 2006 starting at 10 AM as part of the "Talk of the Bay" show at KUSP public radio in SantaCruz, California.
- Link to the NOVA article, "The Contrail Effect" by Peter Tyson
- Jet Trails just water vapor, not sprayed chemicals, experts say : November 29, 2006 Tennessean.com article, by Anne Paine
- Concern Grows Over Pollution from Jets : December 19, 2006 USA Today article, by Gary Stoller.
- Langley Researcher Takes Conspiracy Out of Contrails in USA Today, February 22, 2007.
Spreading contrail examples
DMSP thermal-IR image
showing contrail spreading, diffusion, and thinning, DeGrand et
DeGrand, J. Q., A. M. Carleton, D. J.
Travis, and P. J. Lamb, 2000: A
satellite-based climatic description of jet aircraft contrails and
associations with atmospheric conditions, 1977-79. J. Appl. Meteorol.,
AVHRR image showing a
contrail outbreak over the midwest, Travis et al. (1997).
Travis, D. J., A. M. Carleton, and S.
A. Changnon, 1997: An empirical
model to predict widespread occurrences of contrails. J. Appl.
Meteorol., 39, 1211-1220.
Pseudo-color, multispectral AVHRR images taken April 20, 1994
UTC, and 2230 UTC,
NOAA-12 and NOAA-14, respectively, reveals a considerable number of
contrails over Oklahoma, Kansas, and adjacent areas.
image constructed from November 20, 1995 1-km resolution AVHRR data
over NASA Langley in southeastern Virginia near 1430 Local Time, reveal
a wide-ranging network of contrails both in and out of ambient cirrus
clouds over much of the
October 26 GOES-8
images showing obliteration of Kansas by contrail cirrus. GOES-9
and NOAA-12 images from May
12-13 showing a
NASA DC-8 racetrack contrail, Minnis et al. (1998).
Minnis, P., D. F. Young, L. Nguyen,
D. P. Garber, W. L. Smith, Jr., and
R. Palikonda, 1998: Transformation
of contrails into cirrus during
SUCCESS. Geophys. Res. Lett., 25,
November 13th NOAA-15
over the Southeast showing contrails of various ages. Terra
color image over the Midwest also showing aging contrails, Palikonda et
Palikonda, R., P. Minnis, D. P. Duda,
and H. Mannstein, 2005: Contrail
coverage derived from 2001 AVHRR data over the continental United
States of America and surrounding areas. Meteorol. Z., 14, 525-536.
(For a reprint, please contact firstname.lastname@example.org)
Under certain conditions contrails persist for long periods
of time and can extend over great distances as seen in this
August 13 (1056 UTC) NOAA-16
4-km AVHRR image over the
Pacific. The contrails and cirrus
clouds can be seen in the IR image (lower panel) but the visibility is
greatly enhanced by the use of an IR temperature difference image
(upper panel), Minnis et al. (2005).
Minnis, P., R. Palikonda, B. J.
Walter, J. K. Ayers, and H. Mannstein,
2005: Contrail properties over the eastern North Pacific from AVHRR
data. Meteorol. Z., 14, 515-523. (For a reprint, please contact
NOAA-17 satellite images taken during the morning of March
20, 2004 over the Pacific Northwest show how a contrail outbreak
can appear to be regular cloud cover but is, in fact, mostly spreading
contrails. The image
on the left is a standard infrared satellite image, while that on the
right uses two infrared wavelengths to reveal contrails.
NOAA-17 satellite image
taken at 16:00 GMT of March 6, 2007
and MODIS TERRA satellite image
taken at 16:33 GMT of March 6, 2007 show how a contrail outbreak over the South East U.S.
New Contrail Studies
Contrail formation diagrams: How short-lived and persistent contrails
JPG versions: somewhat blurry (~ 800 kbytes) English, Spanish, French
Search for contrails in satellite
If you would like to see if contrails were visible over your favorite
area on a given day, try viewing our MODIS and AVHRR imagery.
1) Select the day on the pull down menus at the top. GAC data provide
more coverage but at lower resolution. Contrails are better seen in the
HRPT data, but the spatial coverage is not as broad as the GAC.
2) After selecting the day, press "SEARCH". A map is returned with
orbit lines for each satellite carrying the AVHRR instrument. Pick out
the satellite and orbit time you wish to see. All times are given in
UTC or GMT. To find local time, subtract X hours from the UTC
time. X = west longitude / 15. If you get a negative number, add 24.
Example: Say you want central Oklahoma (longitude is
about 97 deg West)
UTC = 13:58, X = 97/15 = 6.5 or
LT = UTC - X = 13:58 - 6:30 =
If daylight savings time, add one
hour to LT.
LT is an approximation to your actual local time because time zones are
very broad. Use this LT cautiously. It should get you to within 1
hour of your desired time in daylight or standard time.
3) Select the desired satellite on left sidebar. Another map appears
giving the orbits only for the selected satellite. On the left sidebar,
the times are listed those images that are actually available on our
server. (If you cannot find them in the HRPT imagery, try the GAC
images if you are really interested.)
4) Click on the desired time (if no times are displayed, you will need
to try another satellite or GAC data). The infrared (chan 4 gray) image
is displayed with a map overlay.
5) Scroll around to see if the area you need is in the image. You can
view the image in false color by clicking on RGB 1,3-4,4 or RGB 1,4,3-4
(NOAA-17 has RGB 1,6,4). under "Channel" on the sidebar. I prefer the
first RGB. You can look at a number of other channels also.
6) The best channel for "seeing" contrails is "chan 4-5". This image is
produced by taking the difference between two different infrared
channels. Contrails typically show up as linear features. Sometimes,
their locations are very easy to discern. Sometimes they can be
confused with other features. THerefore, it wise to look as the
other images to see if they are contrails or some other feature.
7) Try this procedure for NOAA-17, 16 March 2006 at 1706 UTC. You can
see a few over WY, MN, ND, WI, PA, TN, AL, MI, central TX, and the OK
panhandle. But there are hundreds over AZ, UT, NM, and CO. If you look
at the RGB 1,6,4 image, you can see areas covered by snow appearing as
bright magenta. Low clouds are whitish or yellowish. High clouds are
pinkish, or purple, or gray or sometimes white. When the sun goes down,
these images do not look as good because we lose the reflected sunlight
Follow the steps above, but now choose between Aqua or Terra.When you
click on a time, you will see many more channels. Here, the best
contrail channel is "11-12 µm". These images are not as crisp on
the edges as the AVHRR images.
Clouds and Contrails in Motion
If you wish to see cloud changes over the day, we suggest using GOES
data. A large variety of imagery is available for your viewing pleasure
Have a look.
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