POES AVHRR 12.0 µm and MODIS 11.0 µm IR images (with METAR surface reports)

Record cold continued across the interior of Alaska, with Fairbanks reaching a minimum temperature of -50º F on 28 January 2012 and -51º F on 29 January 2012. These were the first -50º F temperatures at Fairbanks since 2006 (NWS Fairbanks public information statements). The coldest temperature reported was -65º F at Galena and by a coopertive observer at Fort Yukon (Fairbanks region temperature and precipitation data).

A sequence of AWIPS images of 1-km resolution POES AVHRR 12.0 µm IR and MODIS 11.0 µm IR data (above) revealed the expansion of surface IR brightness temperatures of -50º C or colder (violet to white color enhancement) during the early morning hours on 28 and 29 January. The coldest surface air temperatures at the times of the IR images included -50º F at Fairbanks (station identifier PAFA) and -60º F at Fort Yukon (station identifier PFYU) and Tanana (station identifier PATA). The signature of cold air drainage into lower elevation terrain (such as the relatively narrow river valleys along the south side of the Brooks Range, and also the broad Yukon Flats) could be seen on the 1-km resolution IR images.

Suomi NPP VIIRS 11.450 µm (Band I5) IR image

The pattern of cold air drainage into lower elevations could be seen in even greater detail using McIDAS images of 375-meter resolution Suomi NPP VIIRS 10.450 µm IR data at 12:06 UTC on 28 January, over northwestern Alaska and the Yukon Territory of Canada (above), and also just to the southwest over the eastern interior of Alaska (below). These 2 VIIRS images use a different color enhancement, where the coldest surface IR brightness temperatures are darker blue.

Unfortunately, there was no surface air temperature report for Arctic Village (station identifier PARC) at this time, but the coldest surface IR brightness temperatures within some of the deeper valleys near that site was -58.4º C (-73.1º F).

To the south, a broad area of very cold (dark blue) surface IR brightness temperatures was seen across the Yukon Flats, with a minimum value of -58.3º C (-72.9º F). The hourly surface air temperature at the Fort Yukon (PFYU) reporting station close to the time of the satellite image was -56º F, while the surface IR brightness temperature at that location was -54º F. Although there is not always a direct 1:1 correspondence between satellite-sensed IR surface temperature values and the actual air temperature measured within an instrument shelter at a height of 5 feet above ground level, the IR satellite imagery can be used to located areas that might have the coldest surface air temperatures.

Suomi NPP VIIRS 11.450 µm (Band I5) IR image

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1-day observed precipitation for 25 and 26 January 2012

Maps of the 1-day total precipitation for 25 January and 26 January 2012 (above) showed that much of Texas and Oklahoma received several inches of rainfall during that 48 hour period.

AWIPS images of the MODIS 0.65 µm visible channel and the corresponding  MODIS Land Surface Temperature (LST) product (below) revealed a large swath of rain-cooled ground across much of that region. LST values where heavy rain fell were in the 60s F (yellow to light orange color enhancement), in contrast to LST values in the 70s and 80s F (darker orange to red color enhancement) to the north and the to the south of the rain-cooled areas.

MODIS 0.65 µm visible chanel image + MODIS Land Surface Temperature product

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Aqua MODIS: 11.0 µm IR images (grayscale, and color-enhanced) + "Fog/stratus product"

A comparison of AWIPS images of 1-km resolution Aqua MODIS 11.0 µm “IR Window” channel data (both grayscale, and color-enhanced) and the corresponding MODIS “Fog/stratus product” (above) showed some areas of fog and/or stratus cloud over the eastern half of Hudson Bay, Canada on 26 January 2012. On the fog/stratus product, low clouds and/or fog appear as the yellow-to-red enhanced features, while cirrus cloud features appear darker black.

The primary feature of interest here is the very thin – almost “translucent” – patch of fog/stratus located in the upper center portion of the image, to the west of Akulivik (station identifier CYKO) and Povungnituq (station identifier CYPX). The exact edges of this feature were difficult to identify in either the grayscale or the color-enhanced IR images — but the conventional “Fog/stratus product” (simply the difference in IR brightness temperature between the 11.0 µm and 3.7 µm channel data) allowed unambiguous identification of the edges.

About 45 minutes earlier, a similar comparison using McIDAS images of of 375-meter resolution Suomi NPP VIIRS 11.450 µm IR data (both grayscale, and color-enhanced) and the corresponding VIIRS “Fog/stratus product” (below) showed much more detail associated with this particular thin fog/stratus feature. The higher spatial resolution allowed many more of the  ice leads to be seen — even some of the larger ones that were located below the thin fog/stratus feature.

Suomi NPP VIIRS: 11.450 µm IR (grayscale, and color-enhanced) + "Fog/stratus product"

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Suomi NPP VIIRS visible and IR images of the eye of Tropical Cyclone Funso

On 24 January 2012 NASA renamed the recently-launched NPP satellite (formerly known as the NPOES Preparatory Project)  the Suomi National Polar-orbiting Partnership (or Suomi NPP) in honor of Dr. Verner Suomi, recognized as “the father of satellite meteorology” (see: NASA News | University of Wisconsin News). A comparison of Suomi NPP 375-meter resolution VIIRS 0.640 µm visible channel and 11.450 µm IR channel images (above) showed the eye of Category 4 Tropical Cyclone Funso, which was located in the Mozambique Channel between Africa and Madagascar at 11:02 UTC on 24 January (track of Tropical Cyclone Funso).

On 25 January 2012, another Suomi NPP 375-meter resolution VIIRS 11.450 µm IR image (below) displayed very cold cloud top IR brightness temperatures (as low as -77º C) associated with a large thunderstom complex over Texas — this storm produced hail up to 1.25 inches in diameter (SPC storm reports) and heavy rainfall of up to 9.29 inches at Uhland (NWS Austin/San Antonio Texas Public Information Statement).

Suomi NPP VIIRS 11.450 µm IR image

The corresponding 4-km resolution GOES-13 (GOES-East) 10.7 µm IR image (below) showed much less structure to the cloud top temperature field, with the coldest IR brightness temperature being -70º C.

GOES-13 10.7 µm IR image

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