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Snow cover in northern Quebec, Canada

Sunday, October 4th, 2009
MODIS visible, 2.1 µm near-IR, and 3.7 µm shortwave IR channels

MODIS visible, 2.1 µm near-IR, and 3.7 µm shortwave IR channels

AWIPS images of the MODIS visible channel, the 2.1 µm near-IR “snow/ice” channel, and the 3.7 µm shortwave IR channel (above) displayed a swath of snow cover on the ground in far northern Quebec, Canada on 04 October 2009. The Environment Canada snow cover analysis at 06 UTC placed a maximum of 21 cm (8 inches) in that area. The area of snow cover appeared bright on the visible image, and darker on the 2.1 µm near-IR snow/ice image (due to the strong absorption of snow at that wavelength) — however, there was a patch of supercooled water cloud over the northern portion of the snow cover, which appeared brighter white on the snow/ice image and darker (warmer) on the shortwave IR image (due to increased solar reflection off the supercooled water droplets).

A comparison of the MODIS visible image and the corresponding MODIS false color Red/Green/Blue (RGB) image constructed using the visible and the near-IR snow/ice channels (below) shows the value of RGB imagery for helping to distinguish between snow cover (which appears darker red on the false color image) and supercooled water droplet clouds (which appear as cyan to white shades on the false color image). Note the semi-transparent nature of this particular cloud deck: surface features (such as rivers, and the edges of the snow cover) can be seen through the thin cloud feature. Farther to the south, glaciated clouds that are composed primarily of ice crystals also appear as varying shades of red on the false color image. The ability to display these types of false-color RGB images will hopefully be available to forecasters using the next generation  of AWIPS-2 software.

MODIS visible and false color RGB images

MODIS visible and false color RGB images

The MODIS Land Surface Temperature product (below) indicated that LST values were only in the 30s F (darker green color enhancement) in the region of snow cover, compared to much warmer 40s and 50s F (lighter green to yellow color enhancement) in the surrounding bare ground areas.

MODIS Land Surface Temperature product

MODIS Land Surface Temperature product

Posted in AWIPS, Arctic, MODIS, Winter weather | Comments Off

Wildfires in the Yukon Territory of Canada

Thursday, July 30th, 2009
GOES-11 IR image with surface reports

GOES-11 IR image with surface reports

The anomalously strong ridge of high pressure that helped to bring record warm temperatures to parts of the Pacific Northwest — which included an all-time high temperature of 103º F at Seattle WA — was also bringing unseasonably warm temperatures as far north as the Yukon Territory of Canada on 29 July – 30 July 2009. A GOES-11 IR image with surface reports (above) showed that surface temperatures were as warm as 93º F (34º C) at Carmacks (station identifier CXCK) and as warm as 82º F (28º C) at Shingle Point (station identifier CYUA) along the arctic coast.

GOES-11 visible images

GOES-11 visible images

These warm temperatures were helping to create an environment favorable for rapid wildfire growth. GOES-11 visible images (above) revealed a number of very large smoke plumes that developed across the Yukon Territory.

The corresponding GOES-11 3.9 µm shortwave IR images (below) showed the presence of widespread fire “hot spots”, with many pixels reaching IR brightness temperatures of 330º K or greater (red pixels) — the hottest pixels exhibited temperatures of 341º K.

GOES-11 3.9 µm shortwave IR images

GOES-11 3.9 µm shortwave IR images

A 1-km resolution NOAA-15 AVHRR Red/Green/Blue (RGB) composite image (below) offered a closer view of some of the fires and their associated smoke plumes. Note the difference in appearance between the rivers in far western Yukon Territory (along the far left side of the image) and the dark blue lakes located farther to the east. The westernmost rivers are fed by the melting glaciers (seen in the lower left corner of the image) and contain a great deal of suspended sediment, which makes their water surface appear very different than that of the lakes.

NOAA-15 AVHRR RGB false color image

NOAA-15 AVHRR RGB false color image

===== 01 AUGUST UPDATE =====

With the aid of a favorable forward scattering angle during the early morning hours, a large plume of smoke aloft from the Yukon fires (with possible contributions from recent Alaska fires as well) could be seen on GOES-11 visible images (below), moving southeastward across parts of the Dakotas, Minnesota, Nebraska, and Iowa on 01 August 2009.

GOES-11 visible images

GOES-11 visible images

Later in the morning, the smoke plume was very evident on MODIS true color imagery (below) as it continued to move eastward over Wisconsin and Lake Michigan.

MODIS true color image

MODIS true color image

Posted in AVHRR, Arctic, Fire detection, GOES-11, MODIS | Comments Off

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