Expectations:
Takeoff: 0730 UT, 0830 LT
Duration: 10 hours
Comments:
A lobe of the vortex continues to extend southward over Scandinavia, reaching the far southern coast of Finland. This air at ER-2 flight levels is predicted to have been below 195 K for one day during the past five days. Cold temperatures still occur over northern Norway and at relatively low latitudes near Iceland. A large mountain wave is forecast in several models for the east coast of Greenland near 73°N. A high tropopause is forecast to the west of Iceland, so we may be in the troposphere there, possibly with clouds present.
Goals:
Flight Report:
Took off at 0745 UTC.
Takeoff time was confused by last-minute changes in the ER-2 flight plan. This resulted in an attempted advance in our takeoff time, which was missed because of experimenters who were not ready in time. Fortunately the ER-2 takeoff was also delayed. PSCs were clearly visible to the naked eye on the sunrise horizon. On climb out the tropopause was near 35 kft in altitude, and an ice fog seemed to fill the upper troposphere. These particle sizes were reported to be around 5 µm by Bruce Anderson, so he should be able to obtain a good surface area. Kondo's group reports that NOy is present on these particles. 200 ppt of gas-phase NOy, particle NOy about 4000 ppt/20. So particle NOy is about equal to gas-phase. Gas-phase HNO3 is only about 20 ppt. Near 70°N PSCs are present in a layer near 20 km. This seems to be a NAT cloud, based on visible depolarization from Hostetler's lidar. At 73°N the PSC dipped down to about 16 km. At 69°N on the return leg the PSCs were as low as 17 km. An upper layer above 23 km was depolarizing in the Hostetler visible channel. We passed through (under) a contrail near 67°N that showed up on some of the in situ instruments; however, we did not clearly intercept our exhaust on the northern turn as we had planned. As we climbed toward 37 kft, we passed through a cirrus layer. Again this showed particulate NOy, low HNO3, and particle sizes that should allow us to obtain a surface area. The outside air temperature at this point was around -70. At 59°20´N we seem to be outside PSCs for the first time. MTP would suggest that we were still in the vortex. We seem to again have missed our exhaust on the turn. The pilots report no feeling of gravity waves over Scandinavia, which they had felt on previous flights. Near 67°N, as we intercompared with the ER-2,we again entered the troposphere and flew through nitric acid-containing cirrus. As we began the sun run, numerous layers of PSCs were visible on the sunrise horizon. The DIAL lidar showed three well-developed layers ranging in altitude from about 17 to 23 km. At 22 km the PSC was clearly polarized. The lower altitude cloud was clearly depolarizing in the visible according to both DIAL and Hostetler's lidar. At 1236 UT the PSC on the horizon remains very distinct. It appears as a white diffuse haze extending well out from the sun, almost from the wing to the nose of the plane. Vertically it extends from the horizon to about twice the angular height of the sun. At 1243 UT we were beneath a highly backscattering cloud (20 in the infrared), and MTP reported temperatures cold enough for ice. It could be that is why this PSC is so visible. The cloud from 21 to 24 km was highly depolarizing in the visible and infrared. The cloud seen from 19 to 20 km had a different wavelength dependence to the depolarization than did the higher-altitude cloud. This cloud seemed so thick that it dimmed the sun to the eye. This cloud extended about 800 km east-west, and must go at least 100 to the south, so it covers at least 80,000 sq. km. The air temperature outside the aircraft is about -68 to -70C. Bruce Anderson reports occasional (0.01 per cm3) particles with about a 1-micron radius. Some very distinct waves were present for about 30 min in the DIAL lidar depolarization. By 1330 UT, the lidar suggests that the ice clouds have vanished, to be replaced by NAT. MTP is consistent. Unfortunately, there is cirrus just above the aircraft that we cannot climb through. There is a large amount of particulate NOy (5ppb/20 = 250 ppt). However, gas-phase NOy is about 350 ppt and HNO3 is about 90 to 100 ppt. At 1350 UT, the cirrus was so dense above the aircraft that it was possible to look at the disk of the sun. At 1400 UT we were no longer in cirrus, but the cirrus remained above us and probably under a Type 2 PSC. The tropopause temperature was 196.5 K. At 1510 UT we observed a distinct wave cloud covering much of the horizon off the left wing. We also flew under a cloud with a high backscatter ratio. Both of these seem to be associated with the coast of Greenland. The DC-8 is also in cloud, we are at 41 kft, and the tropopause is about 42 kft.
At 1525 UT, a dense ice cloud occurred from 20 to 25 km. A wave-train of clouds is present above the aircraft at 1527 UT. The clouds are oriented roughly 45 degrees to the left (west) of the aircraft track, and appear regularly spaced toward the sunset horizon. These are spectacularly colored pink and green. At 1534 UT, the tropopause was at 43 kft as we began the turn to the east. LASE reported scattering ratios in the stratosphere approaching 200 between 20 and 25 km. These clouds show a distinct slope of about 2 to 3 km in the vertical over 300 km in the horizontal. It sloped upward as we flew northwest reaching a peak altitude near 27 km and then sloped downward from the turn and toward the east coast of Greenland.
After we left the coast of Greenland the backscatter dropped close to 10, but the cloud remained depolarizing. MTP shows temperatures on the ice curve above 20 km or so. Cloud base seems to be close to 20 km. Ice crystals are still present near the aircraft according to Bruce Anderson. The in situ cirrus data shows an oscillation with a period near 1100 s. The CN shows several periods of oscillation including 1100 s. At 1630 UT near 0 degrees east, Hostetler's lidar shows a back scatter ratio of 30 and LASE shows about 7. We may have reentered the stratosphere at this point. During the last hour the LASE data suggests that the cloud amplitude is undergoing a quasi-periodic variation with a period of about 20 min of flight time near 20 km. DIAL shows a similar wave, though there could also be a 10-min (flight time) wave. AROTEL reports seeing waves propagating vertically with a wavelength of 7 km up to altitudes of 60 km. AROTEL also reports a 10-min (flight time) period wave between Greenland and Iceland. Note 10 min of flight time is about 130 km in distance.