Expectations:
Takeoff: 0900 UT, 1000 LT
Duration: 10 hours.
Comments:
The cold part of the vortex is located between Norway and Central Greenland. The edge of the vortex is located near the west coast of Greenland. Small mountain waves are forecast for the east coast of Greenland. Low tropopause heights are expected for most of the flight.
Goals:
Flight Report:
Some PSCs were visible on the sunrise horizon while we were on the ramp. These were rather limited in areal coverage and seemed to be mainly located to the south of our location.
Took off at 0856 UT.
At 0915 UT, as the lidars became functional, we observed a layer of PSCs from about 14 to 17 km and another from 18 to 20 km. The lower layer is at the lowest altitude of any PSC so far observed. We enjoyed a beautiful view of the Norwegian coastline. At 0925 UT, DIAL reported a scattering ratio near 2 in the PSCs near 17 km. Although two layers seemed present, essentially the entire region from 15 to 20 km was filled with cloud. The wavelength dependence of the lower portion of the cloud was greater than that of the upper portion. Both the top and base rose as we proceeded west; the rise was about 2 km between 0915 and 0930 UT, indicating the slope is roughly 1%. MTP observes temperatures below the NAT condensation point, but not below the ice frost point. At around 0935 UT, near 14°E and 71°N, the PSC layer seemed to have a distinct break - a new layer built in with a base near 13 to 14 km and a top somewhere near 17 km, with material possibly extending up to 20 km. None of these clouds are strongly depolarizing, but they have some IR depolarizing. These clouds possibly are mixed with liquids and solids. Only the upper layer of this cloud is apparent in the visible lidar return. We are well above the tropopause. Anderson sees scattered particles from 0.5 to 1.5 microns, and Kondo sees particulate NOy. It is rather warm at the aircraft altitude. The gas-phase NOy is about 1.2 ppb. PSCs were clearly visible on the sunrise horizon behind us. They appeared as numerous colorless faint layers extending to 20 degrees or so above the horizon at 1000 UT, at about 73°N, 8°E. The aircraft is leaving a spectacular red contrail behind us in the sunrise horizon. At 1025 UT a very faint PSC was present near 17 km, about 75°N and 1°E. It appeared to be depolarizing at 10 or 20% level in IR. Many faint layers of PSC are still evident on the horizon. DACOM has lost the CO measurement, but is still getting methane and N2O. At 1050 UT (76°N, 12°W) ,a faint layer of PSCs remained from about 16 to 18 km, with possibly another thin layer near 20 km. The IR aerosol depolarization was only in the range of 3 to 8%. Very faint layers of PSCs were also visible on the sunrise horizon.
As we neared the Greenland coast at about 1100 UT, the backscattering in the layer near 19 km increased slightly to about 3. The depolarization in this layer also increased. This layer is relatively thin, but shows structure in the scattering within it. Forecast stratospheric winds are from the west, so we should be flying approximately up the streamline; however, flight level winds are from the southeast at about 10 knots. Forecast winds were from the opposite direction at flight level. AROTEL reported low-amplitude thermal waves. At 77°48´N, 28°, the cloud thickened and stretched from 16 to 18 km altitude. This cloud was depolarizing in the visible and had backscatter ratios near 3, so it was evidently a Type 1a. At 1140 UT. thin (hundreds of meters of less) depolarizing layers appeared above and below the main layer. MTP temperatures remained on the NAT line from 15 to above 20 km., but did not reach ice temperatures. Evidently this cloud is not a wave cloud, but resembles the widespread cloud that we saw in the vortex center during our flight with the ER-2 to 89N on 20 January. Although the top of the cloud has remained at a roughly constant altitude, the base of the layer descended from 19 to 15 km over about a one-hour period of flight toward the west (800 km). The thin, separated layer at cloud top has persisted for about 400 km despite being only a few hundred meters thick and a few hundred meters above the more extensive clouds. At about 1145 UT, DIAL shows that the top of the PSC layer is descending. At the same time the AROTEL temperatures are warming in the 20-km-and-higher region, and so are MTP temperatures. Therefore, cloud top may be controlled by temperature. At between 1200 and 1205 UT, both the top and the bottom of the cloud layer between 15 and 19 km moved up about 1 km. The AROTEL temperatures are consistent with this trend, as are the MTP temperatures and potential temperatures. This behavior suggests the cloud is either controlled by dynamics or temperature. Gas-phase NOy remains about 1.5 ppb. Near 1220 UT, as we crossed the predicted edge of the vortex near the west coast of Greenland, the PSCs abruptly disappeared. At the same time, AROTEL ozone at 18 to 24 km increased by about 500 ppb, signaling that we had left the vortex. In situ ozone increased, in situ water decreased, CO declined, and NOy increased. MTP temperatures also increased above the NAT level. At 1445 UT we made a bumpy crossing of the jet but remained above the tropopause. Interestingly, there are very faint cloud bands on the sunrise horizon. They give the impression of being above the aircraft, but can't be PSCs given the high temperatures above us. The DIAL lidar reports some very faint layers in the 15- to 16-km altitude region. At 1500 UT, these faint layers had vanished. We obtained a long sun run over Canada (more than 60 min) and were able to photograph the sun on the horizon as well.