NOAA 12 at 11:58 - VIL and HSRL show cloud tops around 14.7 km with bases from 12.5-13.0 km. Most of the Ci was west of EVG. The Ci was moving southeast. The VIL and satellite images show that the large patch was 16-30 km to the southwest and had a denser lower layer of Ci which produced a colder feature on the satellite image. The coldest part was 262 K on the VISR image while the HIRS sounder reported 274 K.
NOAA 12 observed the cloud to the southwest at a high zenith angle of 45-47 degrees. The resulting two cloud heights were very high, 14.9 and 16.7 km. GOES 8 was more reasonable reporting 9.7-12.5 km with a few 6.3 km pixels on its eastern edge. The HIRS is plaged by the high scan angle problem again.
Emissivities ranged from 16% for the GOES 8 pixel over EVG to 34% in the center of the cloud to the south west. This number is consistent between GOES 8 and NOAA 12 observations. However the VISR method of using the coldest pixel on the IR image, which was 262 K - 12 K colder than the high NOAA 12 pixel, produced an emissivity of 50%.
Visible optical depths are estimted to be 0.3 (EE=16%)over EVG increasing to 0.8 (EE=34%) on most of the Ci pixels. The 262 K pixel on the IR image would have EE=50% and an optical depth = 1.4.
HSRL came on line at 19:15, 30 minutes after the NOAA 14 overpass. It showed two layers 12.0-13.0 and 14.0-15.0 km. The VIL shows a thin 13 km layer at 18:30 and a layer of dense but small cells from 12.0-13.0 km at 18:40. These clouds were moving from the northwest to southeast from about 320 degrees direction.
NOAA 12 has two pixels on the east and west side of EVG about 25 km away. They both reported heights of 12.5 km.
GOES 8 also had pixels on the east-west sides of EVG and they reported heights of 7.1 and 11.0 km. The GOES 8 cloud heights were a little low, especially the 7.1 km while the NOAA 14 heights were right in the middle of the VIL profiles. Note that the NOAA 12 scan angles were 36 and 38 degrees.
Effective Emissivities for NOAA 14 were 8% and 17% corresponding to optical depths (visible) 0.2-0.4. GOES 8 EE were 17% and 25% corresponding to optical depths of 0.4-0.6.
NOAA 12 passed EVG at 23:11 UT just before the MISTI pass. Its pixels were widely space since EVG was on the edge of its scan. Only two pixels were near EVG, one reporting 16.7 km located 34 km to the northwest and 15.9 km located 59 km to the northeast. These pixels has zenith scan angles > 50 degrees and thus have a high bias because of the excessive scan angle.
GOES 8 scanned EVG at 23:46 UT and reported a range of cloud heights from 4.2 to 14.3 km. The VIL at 23:20 UT showed a physically thin but optically dense layer at 4.2 km. The next cloud layers were Ci from 11.8- 15.2 km. The VIL indicates that the 6.3 and 7.1 km reports of GOES 8 are inbetween cloud layers but the 11-14 km reports are well within the Ci found on the VIL.
Effective Emissivities indicate these clouds were optically thin. NOAA 12 at 23:11 UT found EE=27-33%. This corresponds to a visible optical depth of 0.6. At 23:46 UT, the Ci had move over EVG and was mostly to the southeast. GOES 8 EE were smaller, 6-28%, indicating visible optical depths of 0.1 to 0.6.