MODIS true color and false color images

A comparison of MODIS “true color” and “false color” Red/Green/Blue (RGB) images (above) showed that significant amounts of ice remained in parts of southern Hudson Bay and northern James Bay in Canada on 10 August 2009. On the true color RGB image (using MODIS bands 01/04/03), the ice did not appear as as bright as the surrounding clouds, and had a slightly “light blue” appearance. On the  false color RGB image (using MODIS bands 02/07/07), the ice (along with clouds that were composed of ice crystals) exhibited a darker red appearance, in contrast to the cyan to white colored supercooled water droplet clouds.

Also note the hazy appearance over parts of Ontario, just to the west of James Bay: this was due to smoke aloft from recent fire activity in Alaska and the Yukon Territory.

A map of the departure from normal ice concentration (below, courtesy of the Canadian Ice Service) indicated that there were large areas where the ice  was in the 7/10ths to 10/10ths range above the normal concentration for the date (darker blue colors). The persistence of a deep area of low pressure just south of Hudson Bay (July 2009 mean 850 hPa geopotential height) kept that region (along with much of the eastern US) unusually cold during the summer, which undoubtedly slowed the rate of ice melt in Hudson Bay and James Bay.

Ice Concentration (departure from normal)

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MODIS true color and MODIS false color images

250-meter resolution MODIS true color and false color images from the SSEC MODIS Today site (above) showed a large smoke plume and “fire hot spot” from the 4700-acre “Narraguinnep Fire” that was burning in southwestern Colorado on 08 August 2009. On the false color image, the fire hot spot appears as a large cluster of pink to red  pixels.

The MODIS true color image viewed using Google Earth (below) shows that the fire was located in the far western portion of the Uncompahgre National Forest, about midway between Dove Creek and Dolores in southwestern Colorado. The fire was believed  to have been started by lightning on the previous day.

MODIS true color image (viewed using Google Earth)

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GOES-12 water vapor images

GOES-12 water vapor images (with aircraft location)

Continental Flight 128, en route from Rio de Janiero to Houston on 3 August, encountered severe turbulence over the Atlantic Ocean just north of Hispaniola, according to AP Press reports. Other press reports suggest the turbulence occurred southeast of Puerto Rico (see this one from Bloomberg, for example), but flight tracking software available online shows a flight path that changed north of Hispaniola, presumably in response to the turbulence encountered. The aircraft landed in Miami at 5:30 EDT, or 0930 UTC; according to press reports, the turbulence was encountered an hour before that, or around 0830 UTC. [UPDATE: on-board flight logs (courtesy of John Williams at RAP at NCAR) suggest the flight path change, presumably right after the encounter with turbulence, occurred around 0800 UTC; that data has been superimposed on GOES-12 Imager water vapor (shown above) and window channel imagery (linked below)] What was happening in the satellite imagery at the time?

MIMIC Total Precipitable water shows that the region of turbulence was moistening with time as a tropical wave approached from the east. However, GOES-12 satellite data show only modest convection in the region. For example, the 6.7 micron water vapor imagery from 08:02 UTC shows only scattered convection, although the presence of developing deep convection very near the location of the turbulence to the north of Hispaniola suggests a strong correlation. A loop of the water vapor imagery certainly suggests the presence of a leading edge to the convective development, which leading edge is very close to the region of severe turbulence. Perhaps the two are related, but at first glance this case demonstrates the challenges inherent in predicting damaging turbulence.

(Update on 10 August: two McIDAS-V image loops, courtesy of Joleen Feltz at CIMSS, show the flight position plotted on Water Vapor (6.5 micron) imagery and window channel (10.7 micrometers) imagery derived from GOES-12 Imager data, clearly showing the flight deviation just as the plane flies over deepening new convection just to the north of Hispaniola.)

Cloud-top cooling (below) estimated using the UW/CIMSS Convective Initiation algorithm indicate cooling of 13 K in 15 minutes. Assuming a moist adiabatic atmosphere with a lapse rate of 6.5 K/km, this is vertical growth of 2 km in 15 minutes, equivalent to upward motion exceeding 200 cm per second. The flight data (the dashed line in the figure below) suggest that the airplane flew very close to this developing cumulus tower.

GOES-12 instantaneous cloud top cooling rate (with aircraft flight path)

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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

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

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

===== 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

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

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