G4 Flight in support of FASTEX IOP XXX (prepared by Bob Gall) Date: January 29, 1997 Takeoff time: (approx) 9:00 am Return Time: 4:09 pm Flight Duration: 7 hr 9 min Purpose Satellite imagery showed a long extended frontal region extending almost north-south from 40N up to the west coast of Iceland. From there the front entered a low over eastern Greenland at a latitude of 70N. There was a strong low pressure system in the vicinity of Labrador and a second frontal system from that low extending across eastern Newfoundland then southwest well off the Eastern U.S. The low over eastern Greenland had drawn relatively warm air northward along the Greenland east coast but at flight time had reversed the flow off the ice cap and to the south of the low to westerly. Hirlam products indicated strong mountain wave like activity along the Greenland coast in this westerly flow. Thus a flight was planned to investigate this mountain wave system as well as to study the frontal system south of Iceland. In addition, the Greenland cyclone was forecast to become a major event over Norway and sondes placed south of Iceland would be in adjoint targets to improve predictions of the storm when it would be over Norway in 36 hours. Description of the Flight The initial track was toward a point 61N 22W where the first sonde was dropped at 10:42Z. Drop altitude was from above 41,000 and all drops for the rest of the flight were from above this altitude. The first drop occurred after we began flying over the cirrus associated with the frontal band. We continued northwest to a point 64N 30 W with drops about every one degree of latitude. We came out of the cirrus at about 61N 25 W and reached the turn point at 11:19Z. From there the track was toward mostly west to 65N 50W. Beyond the about 32W the drop frequency was increased to about every half degree of latitude to 44W, and then again decreased to 1 degree of latitude to the turn point at 50W. The purpose of the higher frequency drops was to define the structure of any mountain waves that might be present along the coast. On crossing the Greenland coast, the ground could be seen though through hazy skies. This was partially due to the low sun angles and higher clouds to the south. Much blowing snow could be seen flowing from the icecap toward the lower terrain with great swirls of snow around mountain peaks extending up though the ice. Strong turbulence was encountered as we began flying over the edge of the icecap. Beyond the air was smooth and the icecap, visible through a hazy sky, appeared featureless. The turn point was reached at 12:48Z. At the turn point, glaciers on the western side of Greenland could be seen through thin cirrus. Beyond the turn point at 59W we proceeded south 1 degree then turned eastward parallel to our original track. Drop frequency remained at every 1 degree of latitude until 44 west and then the plan was to increase the drop frequency to every half degree until we reached 32W where the drops would stop. The purpose of this return to higher frequency drops was to again sample any mountain waves that might be present. Unfortunately the data system crashed at 13:26 at about 45W and from that point there were no further sondes released. The data system did not return until near the end of the flight. On passing over the eastern coast a second time, the ground below was in bright sunlight. We encountered only light turbulence as we passed the coast. From there the flight was simply a return trip with little data being taken. Overall Assessment of the Flight We obtained a good series of soundings in the intended adjoint targets that lay south of Iceland. Good data and a good series of soundings were obtained across the coast on the inbound leg across Greenland in the vicinity of the Greenland mountain wave on the coast. Failure of the data system on the return leg was a disappointment but it was still felt that the flight was very successful. Sonde failure rate about 30%, similar to the rate on earlier flights.