The early morning hours of October 16, 2010 were clear with calm winds over the Southern Appalachian region, providing an ideal set up for radiative cooling. The ADAS objective analysis of temperatures revealed some interesting temperature profiles that reflected the nocturnal inversion across the complex terrain of East Tennessee and southwest North Carolina.
The ADAS temperature analysis at 09Z (image above) shows surface temperatures in the Great Tennessee Valley (about 800-1200 ft MSL) mainly in the lower 40s. In the foothills of the Great Smoky Mountains and the sheltered valleys of southwest North Carolina (about 1200-1800 ft MSL), the temperatures drop to between 34 and 40 degrees, matching very closely to observations. These lower temperatures at the base of the mountains reflect colder, more dense air sinking down the mountainsides and collecting in the elevated sheltered valleys.
As we move toward higher elevations, temperatures begin increasing sharply at around 2 kft MSL. ADAS temperatures in this warm layer are between 43 and 48 degrees. This creates the appearance of a “ring” of higher temperatures around the Great Smoky Mountains in the image above. Also note how the higher temperatures across the northern Cumberland Plateau correlate very well to the higher terrain of that area (the highest elevations in this area are below 3000 ft MSL).
As we continue above 3000 ft MSL, temperatures decrease to between 43 and 39 degrees. The difference from the ADAS valley temperatures to the higher “mountainside” temperatures is about 10 degrees. This temperature pattern can also be seen by overlaying the ADAS temperature contours with the topography image (image below).
The RUC sounding at that same time (image below) showed a strong temperature inversion, with maximum temperatures in the warm nose of 54 degrees, and a surface temperature of 44 degrees. Temperatures in the sounding begin to drop off at about 2800 ft, very close to the same level as shown by ADAS. Though actual temperature values between the RUC and ADAS differ, the temperature difference from the surface to the warm nose is about 10 degrees – the same as show by ADAS.
Some observations of minimum temperatures that morning from across the region reflected this temperature inversion:
McGee-Tyson Airport (TYS) @ 981 ft MSL – 41
Sugarland Center @ 1600 ft MSL – 36
Cades Cove @ 1900 ft MSL – 43
Newfound Gap @ 5000 ft MSL – 36
The benefits of using the ADAS temperature analysis are even more striking when we compare it to the LAPS objective analysis of temperature in the image below.
A Frost Advisory was also in effect on this morning, and ADAS temperature analysis helped to get a better idea of which areas may have received a frost or a freeze.