• MODIS Pic of the Day 29 July 2022

    From Dan Richter@1:317/3 to All on Fri Jul 29 12:00:48 2022
    July 29, 2022 - Water in Lake Gairdner

    Water in Lake Gairdner and Island Lagoon
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    South Australia is considered to be the driest of all the Australian
    states, with annual rainfall topping 10 inches (250 mm) in only about
    one-fifth of the region. Summertime (December to February) is the
    driest and hottest season, with most rainfall in winter (June to
    August).

    As a result of the hot, dry climate, the landscape of South Australia
    is speckled with salt lakes, most of which are little more than
    rarely-moistened, mineral-crusted depressions. Many of these are found
    north of the Eyre Peninsula, surrounded by the red sand hills near the
    Gawler Ranges. The largest of these lakes—indeed the third-largest salt
    lake in Australia—is Lake Gairdner. Lake Gairdner, along with Lakes
    Harris and Everard, are so unique that they are protected as part of
    Australia’s Lake Gairdner National Park.

    The bone-dry, extremely flat surface of Lake Gairdner is a place where
    land speed records are set by cars, trucks, motorcycles, and even
    wind-driven land yachts. It’s also the location where enthusiasts meet
    to see just how fast they can accelerate on “the big white dyno”,
    especially during the Dry Lakes Racer’s Australia (DLRA) “Speed Week”
    held at the end of each summer, when conditions on the giant salt flat
    is always perfect. Always—except for this year. In 2022, Lake Gairdner
    was under water. On February 1, the DLRA cancelled the event, citing
    that the lake was under about 500 mm (19.7 in) of “very dirty water”.

    South Australia suffered an extremely wet summer. On January 22, 2022,
    multiple media outlets reported a “once in a lifetime” rain event,
    which dumped 181 mm (7.1 in) at Mt. Ive in three days, which was sixty
    percent more than its annual average. The Australian Bureau of
    Meteorology (BOM) was quoted as saying that several spots in the state
    had received “all-time” highest recorded rainfall totals over 24 hours,
    with at least seven of those located near the Eyre Peninsula. A section
    of the Olympic Dam Highway, a road that runs north of Lake Gairdner,
    was washed away. The BOM attributed the rare summer deluge, at least in
    part, to tropical moisture brought to Australia by then ex-Tropical
    Cyclone Tiffany, which had crossed the northern part of the country
    shortly prior to the southern downpours.

    The torrential rainfall also filled all of the normally salt-encrusted
    lakes in the region, including Lake Gairdner. While rain patterns have
    returned to nearly normal since January, the South Australian salt
    lakes have been slow to dry up. Evaporating is occurring, with
    estimates of up to 100 mm (3.9 in) a month. But it will still be
    several weeks or months before the “big white dyno” is ready to ride.

    On July 26, 2022, the Moderate Resolution Imaging Spectroradiometer
    (MODIS) on board NASA’s Aqua satellite acquired a false-color image
    showing water-rich salt lakes. The image is centered on Lake Gairdner.
    To the northwest of Gairdner is Lake Harris and to the southwest is
    Lake Everard. Island Lagoon is the largest lake to the east of
    Gairdner.

    In this type of false-color image, a combination of infrared and
    visible light (MODIS bands 7,2,1) are used help highlight water. Here,
    vegetation appears in shades of green, with dense vegetation looking
    very bright green, while open land is colored in shades of tan. The
    Olympic Dam Highway, crossing the image in the northeast, is shaded a
    gray-brown. Water within the salt lakes is colored blue, but the shade
    varies depending on the depth. The deepest water is the darkest blue
    and areas that are very shallow, where only a small amount of water
    mixes in with the highly-reflective mineral crust, appear milky-blue.
    Where a thin layer of water sits over the salt layer, or the salt is
    thoroughly saturated, the blue tones tend to be a little muddier or
    duller. White appears along the edge of most of the lakes, where the
    water has completely dried to leave only mineral crust.

    Image Facts
    Satellite: Aqua
    Date Acquired: 7/26/2022
    Resolutions: 1km (127.3 KB), 500m (310.2 KB), 250m (172.7
    KB)
    Bands Used: 7,2,1
    Image Credit: MODIS Land Rapid Response Team, NASA GSFC



    https://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2022-07-29

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