MODIS visible, 11.0 µm IR window, and 3.7 µm shortwave IR images

AWIPS images of the 1-km resolution MODIS visible, 11.0 µm IR window, and 3.7 µm shortwave IR channel data (above) showed some interesting differences in the appearance of convective storm tops over the northern and central Rocky Mountain region on 06 July 2009. Note that some portions of the storm tops appear significantly warmer (darker gray colors) on the 3.7 µm image — this is due to solar reflection off of smaller ice particles within the upper anvil layer. Such differences in cloud top particle size are not apparent on the visible or the standard IR window images (nor do they necessarily correspond to differences seen in the IR brightness temperature patterns on the storm tops). Storms forming with stronger updrafts may produce a higher concentration of smaller ice crystals within the anvil region of the storm top, due to less time for the ice particles to grow in size during their rapid ascent.

View only this post Read Less

GOES-11 visible images

The 2009 wildfire season roared to life in Alaska on 02 July – 03 July 2009, with a number of very large and very intense fires breaking out across interior portions of the state. A ridge of high pressure was in place over the region, allowing Fairbanks to experience a high temperature above 80º F (27º C) on both days. GOES-11 visible images (above) showed some impressive smoke plumes developing on 02 July, especially from the fire located to the east-southeast of Fort Yukon (station identifier PFYU) — note the pulses of “pyrocumulus” that emanated from this >19,000 acre “Little Black One” fire complex:

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
1033 AM AKDT FRI JUL 3 2009

…WILDFIRES BRING SMOKE TO INTERIOR…

THE MAJORITY OF THE SMOKE IS COMING FROM A WILDFIRE KNOW AS LITTLE BLACK ONE. THIS FIRE IS LOCATED NORTHEAST OF CIRCLE IN THE YUKON FLATS. AS OF 230 PM YESTERDAY THIS FIRE WAS OVER 19000 ACRES. CURRENT SATELLITE IMAGERY SHOWS THIS FIRE TO BE CONTINUING TO INCREASE IN AREA.

OTHER SMALLER FIRES ARE ALSO BURNING ACROSS THE AREA. WINDS ARE CURRENTLY BLOWING THE SMOKE FROM NORTHEAST TO SOUTHWEST ON THE FIRES.

The large and dense smoke plume originating east of Fort Yukon continued to drift southwestward overnight, and had moved over the Anchorage area (station identifier PANC) by the morning hours on 03 July.

Also, in spite of the very large satellite viewing angle, another feature that could be followed on the GOES-11 visible imagery was the southwestward movement of fog and stratus from the Arctic Ocean into interior portions of the North Slope region of Alaska after about 06:00 UTC on 03 July. The visibility dropped to less than 1/2 mile at Kuparuk (station identifier PAKU) at 06:00 UTC, with an air temperature at that time of 34º F (+1º C).

GOES-11 visible image

It is interesting to note the presence of a thin volcanic plume (likely from an earlier eruption of the Sarychev Peak volcano in the Kuril Islands) farther to the east, located over the Alaska/Yukon border region (above) — this very high altitude volcanic plume feature is illuminated early in the day (when the sun angle was low, and forward scattering was the highest), but then “disappears” on the visible imagery as the sun angle increases and forward scattering diminishes. In contrast, the low-altitude smoke features become brighter as the sun angle increases during the day, allowing more solar reflection to better illuminate the top of the thick smoke (below).

GOES-11 visible images

GOES-11 3.9 µm shortwave IR images (below) revealed a number of very hot fire pixels (black to red color enhancement) — the hottest pixels in the “Little Black One” fire exhibited an IR brightness temperature of 341.0 K (the saturation temperature of the GOES-11 shortwave IR detectors) at 06:30 UTC. The fire located to the west-northwest of Nenana (station identifier PANN) exhibited IR pixels as hot as 340.0 K at 02:30 UTC. The large area of saturated (red) pixels across the Arctic Slope region at 09:00 UTC was due to sun glint (which also caused the very bright pixels to appear at 09:00 UTC on the visible imagery).

GOES-11 3.9 µm shortwave IR images

A comparison of the 1-km resolution NOAA-16 AVHRR 3.7 µm and the 4-km resolution GOES-11 3.9 m shortwave IR images (below) demonstrates the importance of better spatial resolution for detecting hot fire pixels. The hottest IR pixels in both the NOAA-16 and the GOES-11 images were 330.0º K (darker red color) — but note that the large fire located southeast of Fort Yukon (PFYU) was only as hot as 307.0º K (darker black color) on the GOES-11 shortwave IR image.

GOES-11 3.9 µm + NOAA-16 3.7 µm shortwave IR images

The GOES-11 Wildfire Automated Biomass Burning Algorithm (ABBA) product (below) analyzed the first fire pixels east of the Fort Yukon region around 19:30 UTC on 02 July, several hours before the large smoke plume began to form.

GOES-11 Wildfire ABBA product

View only this post Read Less

GOES-12 visible images

GOES-12 visible images (above) revealed the northward propagation of an large convective outflow boundary across the Bay of Campeche (in the far southwestern Gulf of Mexico) on 02 July 2009. A larger-scale GOES-12 visible image (below) showed that at one point this outflow occupied an area approximately the size of the state of Wisconsin!

GOES-12 visible image

An overpass of the QuikSCAT satellite provided SeaWinds near-surface wind data (below) which showed that there was southeasterly flow across much of the Bay of Campeche region, but the wind speeds increased from about 10-15 knots ahead of the outflow boundary to 15-25 knots behind the outflow boundary (the winds at Buoy 42055 gusted to 21 knots around 12 UTC). The QuikSCAT wind vectors showing speeds of 34-50 knots (yellow to red colors) were not valid, due to rain flags greater than 90%. The air temperature and dew point values barely budged with the passage of this outflow boundary, due in part to the very warm (84º F or 29º C) water temperature.

GOES-12 visible + GOES-12 IR + QuikSCAT winds

AWIPS images of the Blended Total Precipitable Water (TWP) product (below) suggest that the TPW dropped from about 57 mm (2.24 inches, red color enhancement) to around 46 mm (1.81 inches, yellow color enhancement) in the wake of this outflow boundary.

Blended Total Precipitable Water product

View only this post Read Less

Meteosat-9 visible image

A Meteosat-9 visible image at 18:00 UTC (above) showed the presence of a great deal of airborne Saharan dust over the North Atlantic Ocean on 30 June 2009. Due to a favorable forward scattering angle, this dust appeared as a large “hazy” feature between Africa and South America. Also note the well-defined “comma cloud” signature of a strong mid-latitude cyclone off the southeastern coast of South America.

The Meteosat-9 Saharan Air Layer (SAL) tracking product from the CIMSS Tropical Cyclones site (below) displayed a strong signal (darker red colors) of this latest pulse of thick dust beginning to move westward off the coast of western Africa on 30 June.

Meteosat-9 Saharan Air Layer product

This pulse of dust was also apparent on Meteosat-9 Red/Green/Blue (RGB) aerosol tracking product images (below), showing up as a brighter pink feature to the north of a large Mesoscale Convective System that was moving westward across western Africa during the 28-30 June period.

Meteosat-9 RGB aerosol tracking images

After the initial pulse of Saharan dust was seen to move off the west coast of Africa around the end of June, another strong pulse of blowing sand/dust (the brighter pink features) was seen to develop inland over northwestern Africa (across parts of Algeria, Niger, and Mali) during the 01-02 July period (below), with some of this dust reaching the coast on 02 July.

Meteosat-9 RGB aerosol tracking product images

View only this post Read Less