Combined Sensor Program
Tropical Western Pacific Cruise

March 13 – April 13 1996

A report by Brian J. Osborne

1.0 Introduction

This article gives a brief overview of the Combined Sensor Program (CSP) Cruise, which the author had the opportunity to participate in as part of a Memorandum of Understanding between Curtin University (Perth, Western Australia) and University of Wisconsin – Madison. Supported by the U.S. Department of Energy, NOAA and the eight other US institutions from which participants were drawn, the CSP cruise was initiated to study radiative balance and air-sea interactions in the tropical western Pacific. The ship used for the cruise was the largest of the operational NOAA ships, the 303-ft R/V Discoverer.

2.0 Cruise Overview

Figure 1: The Discoverer

The CSP cruise began in Pago Pago, American Samoa, leaving one day ahead of schedule at 7pm local time, March 13. The cruise track took the Discoverer northwest to 1 degree south latitude, and then due west towards Papua New Guinea.

The highlight of the cruise was a 10-day intensive study of the Pacific warm pool region off Manus Island, Papua New Guinea. Measurements taken both on board Discoverer and at the ARM CART site on Manus as the Discoverer slowly approached the island will be used to discern the effect (if any) of the island on meteorological conditions in the area.

Once the Manus Island portion of the cruise was complete, the ship headed due east and finally northeast, docking at Pearl Harbor, Honolulu, on April 13.

3.0 Participants, Scientific Instrumentation, and the University of Wisconsin AERI

Table 1 gives a summary of the institutions participating in the CSP Cruise along with their key instruments. This article will not discuss activities undertaken by groups other than the University of Wisconsin and the University of Miami.

The primary University of Wisconsin instrument on board, the Atmospheric Emitted Radiance Interferometer (AERI), is shown below. The AERI, an advanced Fourier Transform Infrared Radiometer developed by engineers at UW's Space Science and Engineering Center (SSEC), measures atmospheric and oceanic spectral radiances from approximately 525 to 3000 cm-1 at 1 cm-1 resolution.

Figure 2: The AERI Instrument
Table 1: The CSP Suite of Instruments
Institution Instrument Comments
NOAA/ETL† FTIR Upward-looking only
NOAA/ETL Aerosol Lidar
NOAA/ETL Wind Profiler/RASS
NOAA/ETL Flux system 30-ft tower on ship bow
NOAA/PMEL‡ AOML&& Van
NOAA/PMEL Aerosol Van
Colo. St. Univ. Optical raingauges Drop-size distributions also measured
Penn. St. Univ. Sun Photometer
Envir. Canada ASAP Van CLASS Radiosonde Launcher
DOE/LANL+ Raman Lidar
DOE/BNL++ Portable Radiation Package IR Flux measurements
Uni. Mass. Cloud Radar
Uni. Miami All-sky video camera Continuous time-lapse sky view
Uni. Miami Infrared Radiance Thermometers Collaborating with Uni. Wisc.
Uni. Wisconsin AERI Atmospheric/Oceanic Radiance Spectra
Uni. Wisconsin Single Lens Reflex Camera Hourly weather photographs
Uni. Wisconsin Suomi Heat Flux Buoy Experimental prototype
Naval Postgraduate School AVHRR LAC Receiver Real-time satellite images
Footnotes to the table.

The AERI project's immediate goals include providing near-surface radiative measurements for satellite SST validation, investigating further the relationship between emissivity and surface roughness, and investigating boundary layer effects. In addition, the opportunity for cross-validation with other shipboard instruments makes the CSP cruise a superb platform for evaluating other potential capabilities of the AERI.

The instrument has undergone significant improvements since its successful first marine deployment in the Gulf of Mexico last year (Smith et. al, 1996). For that cruise, only downward-looking operation was possible — for the CSP cruise radiance measurements at a total of eleven viewing angles were obtained, five angles each below and above the horizon plus a zenith view.

Supplementing data from the AERI instrument are visual and photographic records of prevailing weather conditions. Hourly visual observations were made 24 hours a day, with the help of Nick Nalli, Bob Knuteson, and John Short. Where possible, recorded parameters were cloud cover, cloud type contamination, precipitation, wave height, sea state, and approximate solar insolation. Photographic images were also taken hourly, during daylight hours, giving us a total of some 300 images which we have loaded onto CD-ROM for ready access.

Peter Minnett from the University of Miami, in collaboration with SSEC, undertook similar radiance measurements with two hand-held, high temporal response infrared radiance thermometers (IRTs) having a spectral response between 9.6 and 10.5 micrometers. This data will provide a useful comparison for the AERI data.

Figure 3: The Suomi Buoy Another cruise-related project at SSEC is the experimental Suomi Heat Flux Buoy, which the UW team deployed while the Discoverer was holding station near Manus Island. Approximately 16 inches in diameter, the buoy was set adrift with a tethered floating heat flux sensor, and an extended drogue. To the SSEC team's delight, two days after deployment and a drift of some 40 nautical miles, the buoy appeared dead ahead during a cruise detour to its estimated position (which was based on a 12-hour old ARGOS satellite fix and scant position history). Nick Nalli, John Short and Bob Knuteson were assisted by Discoverer crew members, above, in the retrieval of the buoy from the ship's 26-ft rigid hull inflatable ulitily boat.


Reference

Smith, W. L., R.O. Knuteson, H.E. Revercomb, W. Feltz, H. B. Howell, W. P. Menzel, N. R. Nalli, Otis Brown, James Brown, Peter Minnett, and Walter McKeown, 1996: Observations of the Infrared Radiative Properties of the Ocean — Implications for the Measurement of Sea Surface Temperature via Satellite Remote Sensing. Bull. Amer. Meteor. Soc., 77, 41-51.

Related sites of interest

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