DC-8 Flight Report for January 14, 2000

 

Takeoff: 00 UTC , 1600 LT (13 January, DFRC, California)

Duration: About 10 hours

Comments:

The vortex center is very cold. There is an extensive region between northern Greenland and Kiruna that should be cold enough for NAT PSCs, and there may be wave-induced clouds both over Greenland and Scandinavia. A particularly large wave amplitude is predicted just to the west of Kiruna. The tropopause is also fairly high off the coast of Norway.

Goals:

  1. Transit to Kiruna - first flight-ready day is 16 January.
  2. Look for PSCs in the vortex and compare their predicted and observed locations.
  3. Look for wave clouds on both coasts of Greenland and over Scandinavia.
  4. Investigate possible structure in tracers near the tropopause.
  5. Overfly the Andoya lidar.
  6. Perform a spiral descent on landing to maximize time at altitude over Scandinavian mountains.

    Flight Report:

    Took off on 14 January at 0008 UTC.

    Clouds overhead and a high tropopause (37 kft) for the first hour of the flight (to about 42°N). Near 62°N (0330 UT), temperatures near 20 km altitude began falling. AROTEL reported temperatures at 20 km near 195 K. MTP temperatures near 20 km also were on or below the NAT condensation curve. The Hostetler lidar reported a fairly strong layer at about 20 km altitude that was depolarizing; aerosol scattering ratios were as high as 0.8. Unfortunately we are probably crossing the streamlines at a high angle so this PSC may have formed well upwind. AROTEL temperatures near 20 km hovered between 195 and 190 K throughout the period from 0330 to 0530. Near 0530 (about 72 N), the PSC seemed to become weaker, and vanished about 0555. DIAL was turned off early in the flight due to a suspicious odor; however, after finding nothing wrong it was turned back on about 0615. At that time the Hostetler lidar reported no PSCs. AROTEL finds that temperatures are not significantly different than they were when PSCs were observed. Around 0635 Hostetler reported a PSC around 23 km with a scattering ratio around 4. DIAL sees this as well. This cloud does not seem to be depolarizing in the visible, but it may be in the infrared. At 0640 the cloud disappeared, so it was about 50 km across. At 0643 layers formed at about 22 km, according to Hostetler, with scattering ratios near 2. This cloud was not depolarizing in the visible, but it might have been weakly depolarizing in the infrared. The region of low temperatures (<195 K) has expanded upward from 0600 to 0640 according to AROTEL. At 0640 DIAL reported many layers of PSC were present from 18 km to 20 km. MTP reports temperatures below the NAT condensation temperature from 16 km upward. These are the lowest temperatures MTP has seen during SOLVE. At about 0705 the PSCs seemed to dissipate again, though something was present near 12 to 16 km on DIAL. The PSCs seem to be present in patchy layers of varying altitude. Another layer began to form near 23 km at about 0710. Hostetler reported a scattering ratio of 1.5 to 3 in this cloud. Again this cloud had no depolarization in the visible, but possible infrared depolarization. This cloud deepened with time and had a scattering ratio of 6 by 0715. From 0715 on, two layers were present, one from 18 to 20 km and the other from 22 to 24 km. These clouds seemed to be depolarizing at both visible and infrared wavelengths. As we crossed the coastline of Greenland a short horizontal wavelength (maybe 10 km), 1 km vertical wave was superimposed on the PSCs. Both PSCs dissipated after leaving the coast, but then returned. It is not clear that passage over the mountains had any significant effect on the clouds. PSCs continued to the coast of Norway. At 0845 the twilight horizon had obvious PSCs. DIAL showed four layers from 18 to 24 km. These clouds were clearly depolarizing. Behind the aircraft on the night side the clouds appeared as a indistinct haze above the aircraft. Ahead of the aircraft on the sunrise side of the sky, they appeared as small distinct white clouds with many fine layers, as well as fine, slightly colored layers that seemed horizontally more extensive. Unfortunately the forward video camera did not seem to do a good job of imaging the clouds. I suspect the white clouds are ice clouds that are forming over the Norwegian mountains due to their relatively high optical depths; however, the lidars did not see any obvious ice clouds above the aircraft. The tropopause in this region is poorly defined, but seems to be at about 37 kft. The visible clouds disappeared once we passed over the mountains, but the lidars continued to see layers up to our descent.