Expectations:
Takeoff: 0915 UT, 1015 LT
Duration: 10 hours.
Comments:
A lobe of the midlatitude air extends southward over Scandinavia. Cold temperatures still over the Atlantic to the west of Norway. A large mountain wave is forecast in several models for the east coast of Norway near 63°N. Low tropopause heights are expected.
Goals:
Flight Report:
The ER-2 took off on time. Its contrail was visible from the DC-8 as we taxied out until the ER-2 passed behind a dense bank of PSCs. To the east of the DC-8 on takeoff, there were obvious individual isolated lee waves, as well as a dense large bank of PSCs.
Took off at 0921 UT, 1021 LT.
The aircraft headed directly into the sun. The nose camera obtained beautiful film of the PSCs. From 0940 to 1020 UT, we remained under depolarizing PSCs. These appear to be mainly Type 1a. They are clearly small wave clouds with IR scattering ratios from 2 to 4. They appear as disconnected wave clouds with varying altitude. Very faint clouds appear as low as 18 km. The most highly scattering clouds are distributed between about 20 and 23 km. These seem to be only a few hundred meters thick and to have considerable structure. There is no obvious non-depolarizing head to these clouds, but the data need to be examined more closely. Also, we are crossing the clouds at right angles to the streamlines, so the heads may be upwind of us. Unfortunately our late takeoff has eliminated much of the possible sunrun. We have reset it to cross this general area a few hours from now. The PSCs in this region are not easily visible from the aircraft. The PSCs disappeared at about 60N, at the edge of the 195-K contour on the 480-K potential temperature surface. They reappeared for about 5 min at 1045 UT near 58N around 20 to 22 km altitude. At the end of the run over Russia. we did turn into our exhaust. We could see this in the Anderson particle counter and Kondo's NOy instrument.
Around 1150 UT, DIAL observed a thin depolarizing layer at about 14 to 15 km altitude. MTP temperatures are too low for PSCs at this time. This could be a small amount of volcanic debris, it could be debris from the meteorite that broke up about a week ago, or it could be an intrusion into the middleworld from the troposphere. At about 1240 UT, near 58N, we began to see a faint enhancement of the background aerosol, and then at 1305 UT we encountered a Type 1a PSC that extended from about 19 to 22 km altitude. It had a scattering ratio from 3 to 5 in the IR and 1.5 in the UV. The depolarization and the wavelength variation of the backscatter varied in magnitude across the cloud, suggesting that the particle sizes varied. At about 1315 UT, faint layers were visible on the sunlight horizon. MTP also saw a temperature wave corresponding to the cloud. The FTIR took spectra at this time. At 1320 UT the PSC was very visible against the sun. It appeared as a set of fine layers with two or three times the solar diameter from top to bottom. The layers extended 5 to 10 solar diameters horizontally at the base and a few diameters near its top. Numerous fine layers extended out at various levels in the cloud. At 1330 UT, the single Type 1a layer split into three thinner layers from 17 to 18, 20 to 21, and 22 to 23 km. In contrast, the cloud on the horizon seemed to have two major layers and many finer ones. The visibility of some of these layers on the horizon suggests that the clouds may contain ice.
At 1410 UT we flew under a relatively dense cloud (IR scattering of 2) that extended from 16 to 19 km. MTP temperatures were low enough for NAT, but not for ice. This cloud seemed not to be depolarizing. The cloud also had a fairly large wavelength dependence, suggesting small particles. At these lower sun angles, the clouds were visible up to about 30 degrees above the horizon. From 1515 UT until our turn back to the east (about 1550 UT), we flew under a series of rather narrow PSC layers that ranged in altitude from 16 to about 22 km. This air should have been some of the coldest in the vortex, but the PSCs looked very different than those on 20 January when we observed a thick, continuous cloud from 16 to 20 km in the vortex center. During the turn back to the east, the pilots attempted to cross our exhaust. It was not certain if we succeeded in this crossing or not.
Crossing the coastline of Norway did not yield any obvious change in the appearance of the PSCs. As we crossed into Sweden a highly depolarizing cloud appeared near 21-22 km. However its backscatter ratio was not large enough to suggest ice. During this time period, the in situ sensors showed slow oscillations with a period of about 10 min of flight time. Near 1705 UT, the PSCs appeared as a series of layers from about 14 to 21 km. From 1715 until 1800 UT, we crossed a long Type II cloud evidently in the location of the predicted gravity wave over Sweden and Finland. No ice was evident in this wave.