Aviation « CIMSS Satellite Blog

Blowing dust in New Mexico, Texas, and Oklahoma

January 22nd, 2012

GOES-15 0.63 µm visible channel images (click image to play animation)

A large outbreak of blowing dust developed in the wake of a cold frontal passage across parts of New Mexico, Texas, and Oklahoma on 22 January 2012. At Lubbock, Texas winds gusted to 60 mph, and surface visibility was reduced to 0.5 mile. The strongest wind gust was 77 mph, farther to the north in the Texas panhandle region (NWS Lubbock summary). Early in the day, the consolidation of numerous smaller blowing dust plumes into a single large blowing dust “cloud” could be seen on 1-km resolution GOES-15 (GOES-West) 0.63 µm visible channel images (above; click image to play animation).

Later in the day, due to a more favorable forward scattering angle, the areal extent of the airborne blowing dust could be better seen on 1-km resolution 0.63 µm visible channel images from the GOES-13 (GOES-East) satellite (below; click image to play animation). The leading edge of the primary large dust plume began to move northeastward over Oklahoma, while a number of smaller dust plumes could be seen moving southeastward across the Oklahoma and Texas panhandle regions behind a secondary cold front. Note that the GOES-13 satellite had been placed into Rapid Scan Operations (RSO) mode, providing images as frequently as every 5-10 minutes.

GOES-13 0.63 µm visible channel images (click image to play animation)

A 250-meter resolution MODIS true color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (below, viewed using Google Earth) displayed even greater detail in the structure of the blowig dust plume at 20:02 UTC.

Aqua MODIS true color Red/Green/Blue (RGB) image (displayed using Google Earth)

There was also a bit of smoke mixed in with the blowing dust, due to a few small wildfires that were burning across the region. Three small wildfire “hot spots” (dark black to yellow pixels) could be seen on an AWIPS image of 1-km resolution MODIS 3.7 µm shortwave IR data at 20:00 UTC (below).

MODIS 3.7 µm shortwave IR image

Over southern Oklahoma at 21:23 UTC a pilot reported that at an altitude of 9000 feet the flight level visibility was zero due to blowing dust (below).

GOES-13 0.63 µm visible channel image + Aircraft pilot report

Posted in Air quality, Aviation, Fire detection, GOES-13, GOES-15, Google Earth, MODIS, Red/Green/Blue (RGB) images | No Comments »

Mountain waves and banner clouds over Wyoming and Montana

December 26th, 2011

GOES-15 (GOES-West) and GOES-13 (GOES-East) 6.5 µm water vapor channel images (click image to play animation)

Strong winds aloft associated with a cyclonically-curved jet streak over the Northern Rocky Mountains were responsible for a number of mountain waves and lee “banner clouds” over parts of Wyoming and Montana on 25 December – 26 December 2011. A side-by-side comparison of GOES-15 (GOES-West) and GOES-13 (GOES-East) 6.5 µm water vapor channel images (above; click image to play animation) revealed some interesting differences in the appearance of these mountain waves. Note that the images are displayed in the native projection of their respective satellites.

A comparison of the GOES-15 and GOES-13 imager 6.5 µm water vapor channel weighting functions (below) showed that the satellite viewing angles (or satellite zenith angles) were very close — 56.41 degrees for GOES-15, and 59.95 degrees for GOES-13 — and the weighting function profiles were nearly identical. However, the fact that GOES-15 was viewing the region from the west allowed it to better resolve the warm/dry signatures (yellow color enhancement) of the most pronounced sinking regions associated with some of the stronger mountain waves. These warm/dry subsidence signatures were possibly masked by the high-altitude lee banner clouds when viewed from the east with GOES-13.

GOES-15 vs GOES-13 water vapor channel weighting function profiles

At 00:40 UTC there was one pilot report of brief moderate turbulence at an altitude of 37,000 feet near the Wind River Range in west-central Wyoming (below). Only a lee banner cloud was evident on the GOES water vapor imagery at that particular time, but a few hours later the warm/dry signature of strong mountain wave subsidence started to become more distinct over that location.

GOES-13 6.5 µm water vapor channel image + pilot report of turbulence

Had higher spatial resolution water vapor imagery been available closer to the 00:40 UTC time of the turbulence encounter, perhaps a more distinct mountain wave signature might have been apparent. For example, a comparison of 1-km resolution MODIS 6.7 µm and 4-km resolution GOES-13 6.5 µm water vapor images at 05:01 UTC (below) demonstrated the advantage of improved spatial resolution water vapor imagery for identifying subtle mountain wave signatures across the region.

MODIS 6.7 µm and GOES-13 6.5 µm water vapor channel images

Posted in Aviation, GOES-13, GOES-15, MODIS | No Comments »

Strong winds affect southcentral and eastern Alaska

December 18th, 2011

GOES-15 6.5 µm water vapor channel images (click image to play animation)

McIDAS images of 4-km resolution GOES-15 6.5 µm water vapor channel data (above; click image to play animation) showed an intense upper level shortwave trough of low pressure moving northeastward across southcentral and eastern Alaska on 18 December 2011. Strong southerly flow associated with this system brought unseasonably warm air into the region, with Anchorage (station identifier PANC) reaching a daily maximum temperature of 45º F (one degree F shy of their record high for the date), and Big Delta (station identifier PABI) tied their daily record high of 37º F. Strong winds were also experienced with this disturbance, with surface winds gusting in excess of 100 mph in southcentral Alaska. It is also interesting to note the development of a small westward-propagating “wave feature” at the end of the water vapor animation near Tanana (station identifier PATA).

Over eastern Alaska the water vapor images also showed a large orographic “banner cloud” that formed downwind of the high terrain of the Alaska Range. A closer look at this banner cloud feature can be seen using an AWIPS image of 1-km resolution MODIS 11.0 µm IR channel data with an overlay of GFS model 500 hPa winds (below). The coldest MODIS IR brightness temperatures along the leading edge of the banner cloud were -65º C, which was just a few degrees colder than the tropopause temperature on the 12:00 UTC Anchorage rawinsonde data. The winds aloft then turned anticyclonically, carrying some of the banner cloud materail eastward into the Yukon Territory of Canada.

MODIS 11.0 µm IR image + GFS 500 hPa winds

The corresponding 1-km resolution MODIS Cloud Type product (below) indicated that much of this banner cloud was of the “opaque ice” category (yellow color enhancement).

MODIS Cloud Type product

The 1-km resolution POES AVHRR Cloud Top Height product (below) indicated that the highest portions of the banner cloud feature were in the 10-11 km range.

POES AVHRR Cloud Top Height product

As an interesting aside, a Boeing 747 flying just off the coast of Alaska encountered severe turbulence at a flight level of 35,000 feet — the captain of the aircraft “said this was the first time he has ever reported severe turbulence” (below).

POES AVHRR 12.0 µm IR image with pilot reports of turbulence

Note on the GOES-15 water vapor images shown above that this area was near the leading edge of an advancing dry slot — and 1-km resolution GOES-15 0.63 µm visible channel images (below) depicted a few cloud features resembling banded convective cells along the trailing edge of the cloudiness just ahead of the dry slot. These convective bands (or the strong deformation axis seen developing on the water vapor imagery) may have been responsible for producing high-altitude turbulence across that region.