QuikSCAT wind vectors + GOES IR and water vapor images

From an email received on the morning of 23 November 2009: “Several hours ago, shortly past 7:00Z today, telemetry received from QuikSCAT indicates that the antenna rotation rate has dropped to zero and remains at zero. The motor remains powered. The system can be operated safely in this state for an indefinite period. The QuikSCAT operations team will be meeting later this morning, but in all likelihood this is probably the end of the nominal mission.”

The image above shows the last QuikSCAT data processed on the AWIPS system at the Cooperative Institute for Meteorological Satellite Studies (CIMSS). The scatterometer wind data show the flow around a developing cyclone located southeast of the southern tip of Greenland. The underlying GOES-12 IR and water vapor images also reveal a classic baroclinic leaf pattern, which is a satellite signature of impending cyclogenesis.

With the loss of QuikSCAT, the only scatterometer winds available in AWIPS are those from ASCAT. For additional information, see the VISIT training modules QuikSCAT Winds and ASCAT Winds.

NOAA-18 10.8 µm IR image

A McIDAS image of the NOAA-18 10.8 µm IR channel (above) showed a region of very cold surface temperatures (darker blue to violet color enhancement) over the interior of Alaska on 19 November 2009, especially in the vicinity of Chandalar Lake (station identifier PALR) and Anuktuvuk Pass (station identifier PAKP). In addition, note the appearance of the warm signature of large cracks or “leads” in the ice over the Arctic Ocean (orange to red color enhancement), to the north and northeast of Kuparuk (station identifier PAKU).

A closer view with an overlay of the surface air temperatures (below) revealed a number of narrow fingers of very cold air — this represented the drainage of the coldest air into mountain valleys along the southern portion of the Brooks Range. The coldest IR brightness temperature in that area was -44º F, which happened to match the coldest surface air temperature from first-order weather stations of -44º F at Bettles (located near the center of the image). Bettles reported record low daily minimum temperatures of -45º F on 17 November, -46º F on 18 November, -47º F on 19 November, and -46º F on 20 November (the high temperature was only -40º F on that day!) — the normal high/low temperatures for Bettles during this period are +3º F and -10º F. This stretch of record cold temperatures followed a record 2-day snowfall of 23.7 inches on 11-12 November (the greatest 2-day snowfall on record for Bettles during the month of November).

However, note that the IR image also suggested the presence of a deck of clouds to the east of the very cold valley signatures — and surface air temperatures were significantly warmer under this cloud deck.

NOAA-18 10.8 µm IR image (with surface air temperatures)

AWIPS images of the AVHRR Cloud Type, Cloud Top Temperature, and Cloud Top Height products (below) indicated that the patch of clouds to the east and southeast of Bettles (station identifier PABT) was composed of supercooled water droplets (cyan color enhancement), with cloud top temperatures in the -30 to -38º C range and cloud top heights in the 3-5 km range. Note that the cloud product algorithms showed values of cloud properties over the region surrounding Bettles (even though it was clear there) — the very cold surface temperatures of -40 C and colder tricked the algorithms into thinking that there were high cirrus clouds over that particular area.

AVHRR Cloud Type, Cloud Top Temperature, and Cloud Top Height products

GOES-11 10.7 µm IR images (below) gave some subtle indication that this cloud deck was moving slowly northward across the region to the east of Bettles (note that north is toward the upper right corner, due to the North America projection of these particular AWIPS images).

GOES-11 10.7 µm IR images