GOES-12 6.5 µm water vapor images

GOES-12 6.5 micrometer “water vapor channel” imagery (above) revealed a pronounced warming/drying signature (darker orange colors) as Hurricane Kyle was beginning the transition to an extratropical system on 28 September 2008. GOES-12 water vapor brightness temperatures were as warm as 268º K (-5.15º C) at 16:45 and 17:02 UTC — and the rapid trend of warming/drying suggested that strong subsidence was occurring in that region.

A comparison of the 4-km resolution GOES-12 and the 1-km resolution MODIS water vapor channel data (below) yielded similar brightness temperature values within the core of the warm/dry region (-5.1º C on MODIS, -7.5º C on GOES-12).

GOES-12 6.5 µm and MODIS 6.7 µm water vapor images

Curiously, the GOES-12 sounder total column ozone product (animation) did not exhibit a high ozone feature co-located with the warm/dry pocket seen on the water vapor imagery (below) — if this dry air were due to a stratospheric intrusion or a tropopause fold, ozone values would normally increase to the 350-400 Dobson Unit range (green to red colors).

AWIPS images of GOES-12 water vapor and total column ozone

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GOES-12 sounder and GOES-12 imager water vapor channels

A fairly large cyclone developed and intensified off the southeast coast of the US on 24–25 September 2008. An animation of GOES-12 sounder and GOES-12 imager water vapor channel data (above) displayed an impressive structure associated with the system, with a well-defined dry slot wrapping around the southern and eastern quadrants of the storm. While not officially acquiring tropical (warm core) characteristics, the storm produced winds gusting as high as 55 mph and waves as high as 19 feet along parts of the Virginia and North Carolina coasts.

A sequence of AWIPS images of the 1-km resolution MODIS water vapor channel (below) showed better details of the storm structure during the period of intensification.

AWIPS images of the MODIS water vapor channel

GOES-12 visible images from 24 September and 25 September (below) revealed some impressive convection forming around the core of the storm.

GOES-12 visible images (24 September)

GOES-12 visible images (25 September)

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GOES-11 and GOES-13 water vapor images

A comparison of GOES-11 6.7µm and GOES-13 6.5µm “water vapor channel” images from 23 September 2008 (above) highlights two important changes to the GOES-13 satellite:

1. the spatial resolution of the GOES-13 water vapor channel imagery has been improved to 4km (compared to 8km on GOES-11), which allows for more accurate detection of mesoscale “mountain waves” (or “lee waves”) that had formed over Wyoming and adjacent portions of Colorado and Montana
2. larger batteries on board GOES-13 allow the satellite to continue to operate through Spring and Fall season “eclipse periods”, when the satellite is in the Earth’s shadow (and the solar panels cannot generate the necessary power for the instruments). The blank GOES-11 images seen in the animation above indicate outages during the GOES-11 eclipse period

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AWIPS images of MODIS visible, snow/ice, and Land Suface Temperature

What do you do on the last day of meteorological summer if you’re in southeastern Nunavut or far northern Manitoba in Canada? You watch fresh snow cover melt! AWIPS images of the MODIS visible channel,  snow/ice channel, and Land Surface Temperature product on 21 September 2008 (above) showed that significant snow cover was in place across that region (which had fallen a few days earlier). The many lakes in that area were still not frozen, and appeared very dark against the surrounding snow cover on the visible image. The slightly darker signal on the near-IR snow/ice image confirmed the presence of snow cover; Land Surface Temperature values were at or just below freezing at many locations (darker green colors), where presumably there was somewhat more snow cover.

The snow cover analysis from Environment Canada (below) indicated that as much as 12 cm (5 inches) of snow was on the ground in that region.

Snow cover analysis

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