[GOES][Landsat MSS][Landsat TM][WiFS]

GOES Images (new GOES 1994 to present)

Dates for clear and dust days were determined based on a detailed assessment of meteorological data available on two NOAA/NCDC websites. Using one web site (CLIMVIS - Global Summary of the Day) we identified dates of potentially low visibility and high wind events in the Southwestern U.S. from 1996 to present. A second web site (Unedited Local Climatological Data) was used to obtain detailed hourly observations at three weather stations bounding the Mojave Desert (Los Angeles, CA; Bishop, CA, and Las Vegas, NV) for dates of possible dust storm events due to high winds. For those possible dates we confirmed periods where the high winds were observed at all three stations and identified periods where water clouds would not potentially interfere with the satellite observation of the Mojave. In reality, such limited ground observations cannot ensure completely clear satellite observing conditions, so we acquired some supporting on-line GOES satellite image data at a third NOAA/NCDC web site (the site is not currently available) to examine the regional distribution of clouds on our candidate clear and dusty days. Many of the images do have water clouds because of their very large regional coverage (all of the western US) and the common association of high winds with cloud-bearing storms, however, the Mojave desert area typically remains mostly cloud-free during wind storms. The GOES image data set has an excellent temporal resolution (15 - 30 minutes), but both the spatial and spectral resolutions limit its usefulness to imaging large dust events (this issue will be reported in more detail later).

To sharply reveal atmospheric changes, temporal image pairs are geometrically registered so that, in general, surface features on each image are at the same location on the screen. In addition, images acquired at approximately the same time of day within a day to a few weeks of each other are used, so surface features have nearly the same solar illumination and surficial reflectance changes are minimal. The automatic blinking between such images allows the eye to detect subtle changes within the two images attributed primarily to the changes in atmosphere, not the ground. We have found this method particularly useful in detecting plumes and clouds of dust. Also included at times in this web page will be digital change image results that isolate primarily atmospheric dust events.

GOES Characteristics

GOES visible-band satellite image April 23, 1997, Temporal Movie 11:00 am - 5:00 pm PST 650 x 375, 1.6 MB

Linked to the thumbnail image (left) is a GOES visible-band satellite movie created from the data set acquired at 15 minute intervals from 11:00 am to 5:00 pm Pacific Standard Time (PST) on April 23, 1997 (note, an image is not present for every 15 minute interval). The movie shows dust blowing across the surface from several sources during the day. The movies on the linked page are available in Apple QuickTime and animated GIF format. To get the QuickTime plug-in (IBM-compatible and Macintosh), click this link to visit the QuickTime Download webpage, http://www.apple.com/quicktime/download/. For those who cannot use Apple Quicktime, a link to an alternative format (animated GIF) will be offered in the Help section of the pages. (Any use of trade, product, or firm names in this publication is for reference purposes only and does not imply endorsement nor support by the U.S. Government nor the administrators and authors of this website.)

Image group 3: Online December 10, 1998

GOES visible-band satellite image April 26, 1997, Temporal Movies Midday and Late Afternoon (PST) 600 x 900, 155 k

Linked to the thumbnail image (left) is a GOES visible-band satellite image composite created from data acquired at 12:00 pm, 12:30 pm, and 1:00 pm Pacific Standard Time (PST) on April 23, 1997 showing the regional setting (highlighted by geographic reference names) used for this image display. Two highlighted areas on the image are linked to temporal movies showing dust forming and blowing across the surface.

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