February 23rd, 2010
AVHRR false color RGB image + map of land boundaries (green)
Andy Heidinger (NOAA/NESDIS/Advanced Satellite Products Branch) pointed out a very long and thin cloud feature, which can be seen near the center of the false color Red/Green/Blue (RGB) image created using AVHRR imagery (above). In this particular RGB image, low clouds appear dark blue, while cirrus clouds are white. The cloud feature of interest (which stretched from the North Slope region of Alaska westward across the Arctic Ocean to the north of Siberia on 23 February 2010) appeared to be over 1000 km long and less than 10 km wide — a perfect candidate for the “What the heck is this?” blog category!
With a strong high pressure cell in place over the North Pole, it is possible that this thin cloud arc marked the leading edge of a relatively weak cold frontal boundary. The southward progress of this cloud feature could be followed on a sequence of AWIPS images of AVHRR 12.0 µm IR channel data (below) — the cloud arc was highlighted with a yellow to cyan color enhancement, representing IR brightness temperatures of -10º to -20º C. In addition, well offshore of the northeastern coast of Alaska you could also see the warmer thermal signature (denoted by the yellow color enhancement) of large thin spots and cracks forming in the the sea ice covering the Arctic Ocean.
It may be pure coincidence, but when this thin cloud arc passed southward across northern Alaska coastal station PAWI (Wainwright), they briefly reported freezing fog and a drop in visibility to 0.5 mile.
AVHRR 12.0 µm IR images
The progression of this cloud band could also be seen on a sequence of grayscale AVHRR composite IR images (below, courtesy of Matthew Lazzara, AMRC). The darker appearance of the cloud arc on the grayscale images supported the idea that this was indeed a relatively warm low cloud feature.
AVHRR composite IR images
AVHRR Cloud Type product
An AWIPS image of the AVHRR Cloud Type product (above) indicated that the cloud arc feature was composed primarily of supercooled water droplets (green color enhancement). The time of the AVHRR Cloud Type image corresponds to the time when Wainwright (station identifier PAWI) reported a brief period of freezing fog as the cloud arc passed southward through the area.
The corresponding AVHRR Cloud Top Height product (below) indicated that the top of the thin cloud band was in the 2-3 km range (darker purple color enhancement).
AVHRR Cloud Top Height product
February 19th, 2010
GOES-12 (top panels) vs GOES-13 (bottom panels) visible channel images
McIDAS images of GOES-12 and GOES-13 visible channel data (above) showed the slow eastward movement of ice across Lake Erie on 19 February 2010. Though not particularly strong, the westerly winds across the region were likely a factor in the ice movement. The improvement in GOES-13 Image Navigation and Registration (INR) is immediately obvious, with significantly less image-to-image “wobble” compared to GOES-12 — this enables the ice motion to be tracked more accurately. Note: GOES-13 is scheduled to replace GOES-12 as the operational GOES-East satellite on 14 April 2010.
A closer view using 250-meter resolution Terra and Aqua MODIS true color images from the SSEC MODIS Today site (below, viewed using Google Earth) revealed that there was still some land-fast ice along the far southern shore of Lake Erie, but most of the ice field was indeed moving eastward during the 103 minutes separating the times of the Terra satellite overpass (16:34 UTC) and the Aqua satellite overpass (18:17 UTC).
Terra and Aqua MODIS true color images (viewed using Google Earth)
An AWIPS image of the MODIS Sea Surface Temperature (SST) product (below) indicated that the water temperatures in the ice-free portions of Lake Erie were in the 32-33º F range (violet color enhancement).
MODIS Sea Surface Temperature product
February 18th, 2010
GOES-13 visible images
With an elongated ridge of high pressure in place along the British Columbia coast on 18 February 2010, nearly cloud-free conditions allowed for some nice satellite views of the Vancouver, British Columbia area (the site of the 2010 Winter Olympics). McIDAS images of GOES-13 visible channel data (above) showed the widespread snow-covered mountains that occupied much of the region, as well as the evolution of some of the cloud features during the day. Early in the animation, some small patches of fog and stratus clouds could be seen burning off as they slowly drifted southward over the waters of the Strait of Georgia. The locations of Vancouver (station identifier CYVR) and Whistler (station identifier CWAE) are indicated on the visible imagery
This animation also serves to highlight the improved Image Navigation and Registration (INR) of the GOES-13 satellite — there is much less image-to-image “wobble” compared to the previous generation of GOES satellites. NOTE: GOES-13 is scheduled to replace GOES-12 as the operational GOES-East satellite on 14 April 2010.
On the NOAA-19 false color Red/Green/Blue (RGB) image (below) using channels 01 (0.62 µm), 02 (0.86 µm), and 03 (3.7 µm), bare ground appears as shades of green to brown, snow cover is brighter white, and stratus clouds over the mountains farther to the east appear as shades of yellow.
NOAA-19 false color Red/Green/Blue (RGB) image
A comparison of 250-meter resolution MODIS true color and false color images from the SSEC MODIS Today site (below) shows even greater detail of the snow-covered terrain features of the region, as well as the few patches of fog/stratus cloud that remained over the northern portion of the Strait of Georgia at 19:07 UTC (where the AVHRR Sea Surface Temperature product showed that SST values were generally in the 40s F).
MODIS true color and false color images