The first Labrador Sea flight on the USAF C-130's was planned to fly into the precipitation along a frontal band ahead of a major low system. The flight was planned to map out the structure and magnitude of the precipitation field in the cloud band. A specially designed box pattern was planned to compensate for our inability to measure the field directly. The plan was to fly around a 'box' 3 times using dropsondes at the corners and middle of the edges to obtain both the change in vertically integrated moisture (or precipitable water) as well as the flux of moisture into the box. Given that the water vapour is a conserved quantity with the only sources or sinks being the precipitation minus the evaporation, the analysis of the dropsonde data should allow us to estimate the P-E.
We had some mechanical problems with the plane, leading to a 3 hour delay in take off and so only 2 of the 3 circuits were completed (still enough for the calculation). Fourteen dropsondes were used in the 9 hour mission.
 |
AVHRR satellite image from the University of Toronto HRPT system, 22:27GMT 26th January. The extensive cloud shield visible is in the warm sector of a synoptic low that moved into the Labrador Sea. Overlaid on the image is the flight track of the C-130, illustrating the box pattern discussed above. |
 |
Mean sea level pressure and precipitation (mm/hour) at 00z 27th January, from the COAMPS model. Note the orographic ppn along south shore of Newfoundland and Greenland. The lack of widespread ppn in the warm sector is thought to erroneous. |