The nearby Vandenberg rawinsonde data profile (below) suggests that the pyroCu clouds vertically lofted smoke to an altitude of at least 6.7 km (the 449 mb pressure level), where winds shifted to a northwesterly direction. However, since the pyroCu cloud-top IR brightness temperatures never even made it to -20º C (cyan color enhancement on the bottom panels), the smoke probably wasn’t much higher than the 6.7 km altitude (sounding data).A comparison of Suomi NPP VIIRS true-color and false-color Red/Green/Blue (RGB) images displayed using RealEarth (below) showed the dense plume of smoke drifting westward away from the active fire area (brighter shades of pink on the false-color image), along with a pyroCu cloud over the fire and the early stage of the southeastward-moving smoke plume aloft.
However, a 1-km resolution NOAA-19 AVHRR 10.8 µm Infrared Window image (below; courtesy of René Servranckx) revealed a minimum cloud-top IR brightness temperature of -48.3º C (dark green color enhancement).A larger-scale comparison of the NOAA-19 AVHRR visible, shortwave infrared and infrared window images is shown below.
===== 23 August Update =====The Pioneer Fire continued to be very active on 22 August (exceeding 100,000 acres in total burn coverage since its start on 18 July), sending a large amount of smoke northeastward (OMPS Aerosol Index). During the following overnight hours, cold air drainage and the development of a boundary layer temperature inversion acted to trap a good deal of smoke in the Payette River valley to the west/southwest of Stanley KSNT. The active fire hot spots (black to yellow to red pixels) were evident on nighttime (1032 UTC or 4:32 AM local time) images (above) of Suomi NPP VIIRS Shortwave Infrared (3.74 µm) data, while illumination from the Moon (in the Waning Gibbous phase, at 69% of Full) showed the ribbon of smoke trapped in the valley (note that this signal was not due to fog, since it did not show up in the VIIRS 11.45-3.74 µm brightness temperature difference or “fog/stratus product”).
During the subsequent daytime hours of 23 August, 1-minute GOES-14 Visible (0.63 µm) images (below; also available as a large 114 Mbyte animated GIF) showed the gradual ventilation of smoke from the Payette River valley as the temperature inversion eroded and mixing via winds increased.
During the subsequent daylight hours, GOES-13 Visible (0.63 µm) images (below) revealed the extent of the valley fog which had formed (the yellow symbols denote stations reporting fog). However, this fog quickly dissipated quickly with strong heating from the July sun.This region frequently experiences such episodes of river valley fog, but they are most common during the Autumn months as nights grow longer and nighttime temperatures get colder. In this late July event, the primary ingredient favoring fog formation was high soil moisture due to recent heavy rainfall (below), much of which occurred on 24 July.