Deep-Sea Reaearch, 1975, Vol. 22, pp. 177 to 184. Pergamon Press. Printed in Great Britain. INSTRUMENTS AND METHODS A small buoy for meteorological measurements at sea CLIVE E. DORMAN* and S. POND'~ (Received 29 July 1974; accepted 5 September 1974) Abstract--A small buoy for meteorological measurements at sea is described. Two buoy tilts, three displacement accelerations, two wave slopes, and the wave height were measured in deep water. These variables were Fast Fourier transformed and analyzed spectrally. The buoy is a surface follower at frequencies up to that of the peak of the wave spectrum (0"05-0'15 Hz). Wave following is important in a meteorological buoy to keep instruments from being soaked. At higher sea wave frequencies, the buoy resists sea motion. The R.M.S. tilts of the buoy are less than 5° and about 0.6 of the R.M.S. sea slopes. Practically all of the buoy motion is concentrated between 0"1 and 0'3 Hz, which results in insignificant buoy motion contamination of much higher frequency turbulence measurements (which are in the range of 1-103 Hz) or in lower frequency mesoscale-macroscale measurement at frequencies less than 3 × 10-3 Hz. INTRODUCTION METEOROLOGICAL measurements at sea could be facilitated by a small, inexpensive, easily handled buoy with the appropriate motion characteristics. Such a buoy, its motion characteristics, and some of its possible applications are discussed in this paper. EQUIPMENT Basically, the buoy (Fig. I) is a triangular television tower 15 m long with a weighted foot and six fibreglass toroids around the center to provide buoyancy. The toroids have an outer radius of 0.61 m, an inner radius of 0.31 m, and a thickness of 0.31 m. The overall mass of the buoy is about 550 kg. Wave poles and buoy motion instruments are attached. The motion instruments consist of a vertical gyroscope and a linear accelerometer. The gyroscope (Humphrey model no. V624-0801-1)measures pitch angles up to 4-90 ° and roll angles of up to +60 °. Static error band of pitch is 1.25% of full scale at 0 °, that of roll is ±0.83% of full scale at 0 °. An accelerometer (Humphrey model no. LA73-0101-1) measured linear accelera- tions in three orthogonal axes. The range in the horizontal axis was ±lg, ±l g, in the vertical axis, about a +l g bias. The accuracy of the accelerometer was 4-1% of full scale. Three wave poles were used to measure wave slopes and height. They were arranged in the corners of a horizontal right triangle, the legs of which measured 1 m, and were held off the buoy by rigid arms. The wave poles were 6. l m long, 2.4 cm dia. threaded PVC. NiCr wire was wound in the threads of the poles to provide the resistance path. *School of Oceanography, Oregon State University, Corvallis, Oregon 97331, U.S.A. Now at Department of Geology, San Diego State University, San Diego, California, 92115, U.S.A. tNow at Institute of Oceanography, University of British Columbia, Vancouver, B.C., Canada. 177