GOES-13 0.63 µm visible channel images

McIDAS images of GOES-13 0.63 µm visible channel data (above) showed the hazy signature of a dense veil of airborne Saharan dust over South Florida and the adjacent offshore waters of the Gulf of Mexico and the Atlantic Ocean on 25 July 2012. This particular major pulse of Saharan dust began to move westward across the Atlantic Ocean during mid-July.

A closer view using an AWIPS image of Suomi NPP VIIRS 0.64 µm visible channel data (below) also showed the hazy signature of the dust over the southeastern portion of the satellite scene. A pilot reported flight visibility of 4 to 5 statute miles within the dust layer over the Florida Keys.

Suomi NPP VIIRS 0.64 µm visible channel image + Pilot reports

A comparison of the VIIRS 0.64 µm visible image with the corresponding VIIRS 11.45 µm IR image (below) demonstrated that there was no dust signal at that particular IR wavelength, due to the fact tht an elevated dust layer is generally transparent to thermal radiation from the land and ocean surfaces below.

Suomi NPP VIIRS 0.64 µm visible channel + 11.45 µm IR channel images

The VIIRS Aerosol Optical Thickness product (below) showed a strong signal (yellow to red color enhancement) over that region due to the presence of the airborne dust. Yet another strong pulse of Saharan dust could be seen exiting  the coast of Africa and moving westward across the Atlantic Ocean,

Suomi NPP VIIRS Aerosol Optical Thickness product

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Suomi NPP VIIRS 0.64 µm visible channel images

Even though most of Hudson Bay in Canada was essentially ice-free on 24 July 2012, there were still some ice floes consisting of thick first year ice that remained in the far southwestern part of the Bay. AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel data (above) showed the motion of these ice floes (along with the other cloud features in the region) between 17:50 and 19:29 UTC.

A comparison of a VIIRS 0.64 µm visible channel image with the corresponding 3-channel Red/Green/Blue (RGB) image created by using 0.64 µm, 1.61 µm, and 11.45 µm data (below) demonstrated the utility of using RGB imagery to help discriminate between ice features (darker purple color enhancemnt) and clouds (varying shades of white).

Suomi NPP VIIRS 0.64 µm visible channel + false-color Red/Green/Blue (RGB) image

Similarly, a comparison of a MODIS 0.65 µm visible channel image with the corresponding RGB image created using 0.64 µm and 2.1 µm data (below) showed the ice features as darker red, compared to supercooled water droplet clouds (lighter shades of white) and glaciated clouds (lighter pink color enhancement).

MODIS 0.65 µm visible channel + false-color Red/Green/Blue (RGB) image

The MODIS Sea Surface Temperature (SST) product (below) showed SST values in the middle 30s F (darker blue color enhancement) over the ice floe features, compared to SST values in the low-middle 40s F over the adjacent open waters of Hudson Bay.

MODIS Sea Surface Temperature product

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MODIS Estimates of Lake Surface Temperature

Persistent heat over the upper Midwest and Eastern United States for the first half of 2012 have helped warm Great Lakes surface water temperatures. MODIS estimates of Lake Surface temperature, above, show only a small region of temperatures cooler than 60 F in the entire Lake system in a very small region near Isle Royale in Lake Superior. (Click here for maps of Lake Superior temperatures. You can also find data for Lakes Huron, Michigan, Erie and Ontario). All other temperatures exceed 60 F. The 8-day average of MODIS SSTs over the lake, from Terra and from Aqua, obtained from this interactive site also shows the warmth. An SST image from AVHRR (the image doesn’t include all of Lake Superior) also shows warm temperatures.

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FY-2E 0.73 µm visible channel images (click image to play HD animation)

A major flooding event occurred in the Beijing, China area on 21 July 2012, as the heaviest rainfall in over 60 years caused at least 77 fatalaties, cancelled over 500 airport flights, and forced more than 65,000 people to be evacuated. Much of the city averaged around 7-9 inches of rainfall within a 10-hour period, with the heaviest total rainfall accumulation being 18.1 inches (460 mm) in the Fangshan District of Beijing. McIDAS images of 1.25 km resolution 0.73 µm visible channel data from the Chinese FY-2E satellite (above; click image to play HD animation) showed an elongated band of clouds with embedded thunderstorms oriented from southwest to northeast across much of northeastern China. The small green box denotes the location of Beijing International Airport.

While there are some navigation issues associated with the FY-2E satellite (as noted by the amount of image drift during the animations), the position of the satellite at 105º E longitude offered a good viewing angle for this particular event. For a more detail meteorological analysis, see “Beijing flood of 21 July 2012” by Richard Grumm, NWS State College PA.

5-km resolution FY-2E 10.8 µm IR channel images (below; click image to play HD animation; also available as a QuickTime movie) revealed the development of very cold cloud top brightness temperatures (-60 to -75º C, red to black to white color enhancement) with some of these embedded thunderstorms, with evidence of a period of back-building of convection in the vicinity of Beijing after around 15 UTC.

FY-2E 10.8 µm IR channel images (click image to play HD animation)

5-km resolution FY-2E 6.8 µm “water vapor channel” images (below; click image to play HD animation) indicated a pronounced warming/drying signature (yellow colors) associated with a deepening shortwave trough that was approaching from the northwest. This approaching trough may have played a role in helping to enhance synoptic-scale upward vertical motion across the Beijing region, creating a more favorable enviroment supporting the formation and maintenance of strong convection.

FY-2E 6.8 µm water vapor channel images (click image to play HD animation)

A comparison of 375-meter resolution Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel imagery at 05:16 UTC (below) showed the development of some of the initial areas of embedded deep convective elements just to the southwest (upstream) of Beijing (station identifier ZBAA).

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

A time series of Beijing rawinsonde data Skew-T plots (below) showed the moistening of the atmosphere on 21 July, with the total precipitable water peaking at 50.4 mm (1.98 inches) at 12 UTC. The subsequent arrivial of dry middle-tropospheric air associated with the approaching shortwave trough can be seen after 00 UTC on 22 July, as Precipitable Water (PW) values dropped to 26.4 mm or 1.04 inch by 12 UTC.

Beijing, China rawinsonde data plots

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