SUMMARY of LEAR FLIGHT #3
Monday 20/1/97 from St. John's, Newfoundland (YYT: 47.5N, 53W)
to Bermuda (BDA/TXKF: 32.4N, 64.7W)
to St John's, NF
all locations, altitudes, winds & temperatures at launch location are from controls & GPS in airplane cockpit (i.e. pressure altimeter) and aviation conversion tables, not from dropsondes. all information except launch locations is approximate.
TAKEOFF: 8:55 Z from YYT (scheduled for 9:00Z). 5:25 local time.
LANDING: 14:17 Z at BDA. 10:17 local.
FLIGHT TIME: 5 h 22 min
Total distance: approx. 1700 miles
CREW:
Pilot: George Kickhofel (Flight International)
Co-pilot & navigator: Gordon Stevendon ( " )
Dropsonde operator & refreshments coordinator:
Dean Lauritsen (NCAR)
On board scientist & tropical vacation coordinator:
Rebecca Morss (MIT)
FLIGHT PLAN:
YYT -> 37N 45W, time of arrival = 11Z
-> BDA
drop ~ 4 sondes on 1st leg, 1 at corner, ~ 12 on 2nd leg, maintaining
altitude & drops as close as possible into Bermuda.
to ease navigation and air traffic control coordination, drop locations were preselected at whole number latitude and longitude coordinates. the flight path was thus nearly, but not entirely, direct.
Recover in BDA, return to YYT with no drops, in time to prepare
for possible Wednesday flight out of St. John's.
DROPSONDES:
it takes an average of 30 seconds after launch for sonde to begin tracking satellites & obtain wind data (using GPS). several sondes took much longer to obtain winds; if the loss of data appeared significant, another drop was performed. thermodynamic data was still recorded in these cases (generally within 10 seconds of launch).
Units conversions:
35000 ft = 10.7 km = 239 mb
39000 ft = 11.9 km = 197 mb
41000 ft = 12.2 km = 179 mb
to obtain m/s from knots, divide by 2
Before each dropsonde launch, a message was sent out on radio giving the location, altitude, and time of launch and requesting any aircraft within 40 miles to notify us. We never got a response, nor did we hear any radio communications at all from aircraft in the vicinity.
Takeoff from St. John's:
snow, wind, low cloud cover
Leg 1:
1. 9:28 Z 45d 59.95' N, 49d 59.99' W 35000 ft
T=-45C winds from 155deg at 90 knots
at launch location
tracked sonde on 2 signal detection channels (1,4). no launch detect
from sonde (parachute did not deploy or deployment was not detected), no wind data on either channel. decided to redrop.
2. 9:34 Z 44d 24.30' N, 49d 38.38' W 35000 ft
-46C 168deg at 104 knots
launch detect, wind data ok (channel 2).
beginning of beautiful sunrise.
3. 9:49 Z 42d 59.63' N, 49d 00.27' W 35000 ft
274deg at 106 knots
tracked sonde on 2 channels (1,3). no wind data on channel 3;
decided not to reuse channel. shallow turn after launch.
100% stratus below flight level.
in-flight cabin & cockpit muffin service by Dean (mmmm! crew is
very grateful). unfortunately, no drink tray due to insufficient space
on board.
4. 10:13 Z 40d 59.09' N, 46d 55.98' W 35000 ft
-56C 197deg at 103 knots
tracked sonde on 2 channels (1,4); both ok. no wind data above
8.3 km.
90% thin stratus below flight level, into 50% cirrocumulus just
after launch.
90-100% humidity in lower atmosphere.
5. 10:32 Z 39d 01.18' N, 46d 00.65' W 35000 ft
-54C 212deg at 89 knots
90% stratus, 2nd layer visible below.
90-100% humidity in lower atmosphere.
cleared by ATC to climb to 41000 ft; began climb at approx 10:42 Z.
turbulence at 38000 ft.
6. 10:51 Z 37d 00.06' N, 45d 02.12' W 39000 ft
-58C 206deg at 118 knots
turn to leg 2 approx 90 sec after launch; slightly weaker signal.
90% stratocumulus just below flight level, stratus layer below.
95-100% humidity, 670mb - 900 mb; 90-100% below 950mb. 16C at surface.
Leg 2:
slow ground speed (300-320 knots) due to headwinds.
7. 11:10 Z 37d 59.95' N, 47d 03.01' W 41000 ft
-54C 210deg at 126 knots
shallow turn 100 sec after launch.
100% stratus below flight level, very thin cirrus near flight level.
90-100% humidity, 700-800mb. 16C at surface.
8. 11:32 Z 36d 00.32' N, 48d 58.91' W 41000 ft
-54C 208deg at 129 knots
shallow turn 45 sec after launch.
50% cirrocumulus below flight level, in 2 layers. whitecaps visible on ocean below.
100% humidity near 750mb only. 0C at 740mb. 18C, 1020mb at surface.
9. 11:51 Z 36d 00.53' N, 51d 01.89' W 41000 ft
-52C 218deg at 130 knots
10% cirrocumulus below. whitecaps visible.
0C at 770mb. 15C, 1020mb at surface.
10. 12:09 Z 35d 59.75' N, 53d 00.15' W 41000 ft
-52C 203deg at 134 knots
shallow turn 45 sec after launch. 7th inning stretch for crew.
70% stratocumulus below.
90% humidity near 770mb only. 0C at 830mb. 15C, 1022mb at surface.
11. 12:32 Z 35d 00.04' N, 54d 59.48' W 41000 ft
-52C 200deg at 123 knots
shallow turn 30 sec after launch. sonde geopotential altitude approx 12.5 km too high due to bit error at launch detect.
10% cirrocumulus below. few whitecaps visible.
15C, 1022.7mb at surface.
12. 12:51 Z 34d 59.56' N, 57d 01.62' W 41000 ft
-50C 204deg at 145 knots
shallow turn after launch. no wind data above 10.5 km. decided to drop additional sonde.
20% small cumulus below.
14.7C, 1023.6mb at surface.
13. 12:57 Z 34d 44.90' N, 57d 34.61' W 41000 ft
-52C 200deg at 137 knots
10% small cumulus below.
14. 13:14 Z 33d 59.85' N, 58d 59.64' W 41000 ft
-51C 200deg at 121 knots
shallow turn 30 sec after launch.
20% cirrocumulus below, 2 layers. no whitecaps visible on ocean.
15. 13:26 Z 33d 43.87' N, 60d 17.92' W 41000 ft
-54C 203deg at 118 knots
10% scattered cumulus. no whitecaps visible.
0C at 850mb.
16. 13:37 Z 33d 29.90' N, 61d 23.48' W 41000 ft
-53C 207deg at 131 knots
shallow turn after launch. no wind data above 9 km. decided to drop additional sonde.
30% scattered cumulus. no whitecaps visible.
drop 16 at Hench (entry into Bermuda radar controlled area). no traffic in area, so were cleared to continue dropping from 41000 ft.
17. 13:44 Z 33d 17.32' N, 62d 03.60' W 41000 ft
-53C 206deg at 124 knots
sonde launched before data collection started (< 10 sec), but data ok.
10% cirrocumulus. no whitecaps visible.
14C, 1024.7mb at surface.
18. 13:53 z 32d 57.68' N, 62d 53.69' W 41000 ft
began descent after launch. obtained complete data from sonde 18 despite descent of plane below sonde for 1/2 of drop and 75NM lateral travel of plane during drop.
20% cirrostratus. no whitecaps visible.
Descent into Bermuda:
turbulence at 16000ft, approx 50NM east of Bermuda.
cumulus layer and turbulence at 3000-5000ft altitude.
rainbow visible at 1500ft altitude, approx 5NM east of Bermuda.
sunny and warm for us in Bermuda, but cool and cloudy according to the locals.
Return ferry flight:
takeoff: approx 16:55Z from BDA
landing: approx 19:45Z at YYT (beautiful sunset)
flight time: approx 2h 50min