SUMMARY OF COAST FLIGHT 5

Date: Thu, 31 May 2001 10:54:48 -0400
From: JOHN M BANE
To: coast@OCE.ORST.EDU
Subject: May 30 Aircraft Report

COAST Flight Number 5 was completed on May 30, 2001. The flight covered the Big Box from north to south. Measurements began on Line 1 about 1400 PDT and were completed on Line 8 about 1930 PDT. A short stop at the Newport Airport was made for refueling after flying four lines. This will likely be a standard practice for subsequent flights covering the Big Box, as completing the pattern non-stop leaves us with the minimum fuel reserve.

Measurements were made of: SST, ocean color, and ocean subsurface temperature; atmospheric winds, temperature and humidity. This was a particularly good day for ocean color measurements, and our reading of the color spectra aboard the aircraft (a high-tech version of phrenology) showed good color variation from nearshore (higher "green" values) to offshore (lower "green" values). We passed the R/V Thompson near the inshore end of the Cape Perpetua line and the R/V Wecoma steaming west on Line 5. Numerous fishing boats were observed in about three regions, one of them at the Thompson's location.

AXBTs were deployed on four lines: 2, 4, 6 and 8. BTs worked at all stations. Deployments were as follows:
Line 2: 6 AXBTs
Line 4: 6 AXBTs
Line 6: 7 AXBTs
Line 7: 6 AXBTs

We continued to have data dropouts from some of the AXBTs after about 2-2.5 minutes of drop (that equals about 180 to 230m depth) due to the sea state. The surface element of the AXBT, which contains the radio transmitter, rides up and down on the surface waves, and so when the wave state is high enough and the aircraft is far enough away the radio signal received at the aircraft becomes intermittent due to the transmitter dropping into wave troughs. These dropouts make post-flight recovery of good data in the deeper portion of an AXBT trace difficult. If the BT hits the bottom prior to the 2-2.5 minute mark, the data loss is of course of no concern. We tried a simple fix for this on a few BTs in deep water on this flight: Just after launching a BT, we turned the aircraft through a "standard rate turn," which is a 360 degree turn in two minutes. This keeps the aircraft near the BT for long enough that we are able to receive a complete profile. We plan to do this from now on with the deep-water BTs.

SST profiles showed little cool water near the northern end of the BB, consistent with the recent weak northerly winds there. The cool water band widened as we flew south, consistent with topographic effects and the stronger northerly winds there during May 29/30. The clear skies of May 30/31 have provided very nice SST images, also.

We flew a two-cycle "sawtooth" pattern (climb from 60m altitude to 800m altitude, descent to 60m, then again to 800m, then finally to 60m) along each of Lines 1, 3, 5 and 7. The onshore extent of each pattern was about 5 km off the coastline, and the offshore extent was just west of 125W. We also have begun flying an alongshore climb or descent at both ends of each of these lines to provide data that will extend the coverage of data obtained on the "sawtooths."

A nice atmospheric temperature inversion was seen at all locations near 400m height. Boundary layer winds were strong and from the north in the southern portion of the BB, with maximum speeds around 25-30 knots. There was a nice jet structure to the boundary layer airflow there, with the speed maximum often collocated (roughly) with the base temperature inversion. Although there was a temperature inversion over the northern BB, the winds were weaker than in the south, and direction was more northwesterly.

(Disclaimer - These descriptions are from looking at computer graphical displays while aboard the aircraft, and closer inspection of post-flight data products will provide more accurate conclusions, some of which may differ from statements here.)

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

Submitted by:
John Bane
May 31, 2001