EPIC2001 Ronald H. Brown

Report #1

C. W. Fairall et al.

September 12, 2001

The RHB departed San Diego about 4 pm local time on September 5 and set a course for the EPIC2001 experimental area. A reasonably efficient course takes us through the national waters of Mexico, so we are unable to acquire data except for test/calibration purposes. After rounding the southern tip of Baja California, we set a course that would take us into international waters a few days before reaching the experimental area at 10 N 95 W.

On September 8 we stopped for approximately 3 hours to test various systems including the CTD, the MMP (University of Washington modular microstructure profiler), the SPMR (University of California at Santa Barbara solar radiative flux ocean profiler), and the balloon sounding system. All tests were successful. Conditions were already quite tropical with air temperature around 28.5 C and sea temperature around 30.5 C. Late on September 9 it began to rain intermittently.

Approximately 0800 GMT on September 10 we entered international waters at about 14 N and 103 W and began recording data. Weather was rapidly worsening and it turns out we were in the center of a tropical disturbance that was fast becoming a tropical storm. Winds increased steadily and reached a peak of 18 m/s (half hour average) at 1800 GMT before declining rapidly. We received about 30 mm of rain in this event (over about 12 hours). The CSU group recorded some dandy C-band radar images of a tropical cyclone in its formation stages. The ETL flux system showed a peak cooling rate of the ocean of 700 W/m^2 at 1800 and the average net heat loss of the ocean was 266 W/m^2 for the day. This is about 10 times the typical daily average in the tropics. The driving rain did cause one unfortunate event by shorting out a connector on the cloud radar/radiometer van and shutting off the power. When power was restored, the computer that controls the microwave radiometers was sick and we are investigating ways to rebuilt its capabilities. The radar and mailbox radiometer are functioning normally. The Doppler lidar, ceilometer, wind profiler, and various ship systems are functioning normally. The UNAM chemistry and aerosol system is running, but a problem has been encountered with the gas chromatagraph that is intended for analysis of DMS concentrations in the sea water samples from the CTD rosette. Amparo Martinez is presently awaiting advice from the manufacturer on diagnosing the problem.

On September 12 at 2200 GMT we reached the TAO buoy at 12 N 95 W and John Shanley commenced replacement of a guano-fouled rain gauge. Apparently the anti-bird spikes had failed (or had fallen off) and the rain gauge became a prime bird resting spot with the predictable results. The weather is once again fine with near surface air temperature about 27.5 C , RH 80%, and sea temperature about 28.6 C. Winds are from 315 at 3.0 m/s. A CTD was done at this site and one is planned for 11 N on the way to the next buoy.

On September 13 about 0130 GMT we had a short radio conversation with the R/V New Horizon. They expect to arrive in the experimental area about 1 day after we do. Despite the tragic events in New York and Washington DC, we intend to continue with our scientific efforts as planned.