SUMMARY OF COAST FLIGHT 17

COAST Flight Number 17 was flown on August 11, 2001. This flight was conducted to capture the system at the end of a brief period of southerly winds in the region, which were due to the passage of a southerly surge. Measurements were made of: SST, subsurface ocean temperature and upper-ocean color; atmospheric temperature, humidity and horizontal winds. Data were collected on all eight Big Box Lines, flying from south to north.

AXBTs were deployed as follows:

Line 2: 6 AXBTs
Line 4: 6 AXBTs
Line 6: 7 AXBTs
Line 8: 7 AXBTs

A distinct atmospheric temperature inversion was observed on all lines where meteorological profiles were made (Lines 1, 3, 5 and 7). It was the sharpest inversion we have seen on any COAST flight, with an abrupt change of about 8C at around 500m height. There was a hint of a wind jet below the inversion, but for the most part the winds were northerly at about 10-15 knots in the marine layer, and weaker and from the northeast above the inversion. There was a widespread stratus cloud layer with the layer top coincident with the inversion. Cloud bases were near 300m almost everywhere, so we were able to fly below the stratus layer for AXBT deployments. Horizontal visibility below cloud bases was quite good (well over 10 miles).

The SST field reflected the northerly winds, with slightly cooler water near the coast. As the winds had just changed around to moderate and northerly, the nearshore SSTs were cool but not the lowest we have seen this summer. We once again saw the sharp, nearshore SST front in the Cascade Head/Lincoln City area. The Thompson reported crossing this front within the past day or so as well. We flew another zig-zag pattern at about 500 ft, crossing the front several times, so we should be able to map it reasonably well on this day.

Satellite SST images taken during the past few days show what appears to be a cyclonic eddy centered at about 44.5, 125.5. We were not able to discern this SST signature while aboard the aircraft, but a more careful look after processing (especially editing out the radiometer data while in or above the stratus clouds) may show that we measured at least the eastern flank of this feature.

We did not see either ship as we flew, and this was likely due to passing each ship while above the stratus cloud layer collecting atmospheric profile data. As the forecast is for northerly winds during the upcoming week, we hope to fly again on August 13, and then continue roughly every other day for several flights. We may revise this plan if the winds do not continue to be from the north.

Data products will be available from http://www.marine.unc.edu/cool/COAST or they may be retrieved from the real-time results or 4-days-plus results areas. All of these are buttons off of the main COAST site.

Submitted by:
John Bane
August 12, 2001