Western Pacific westerly wind bursts of 1‐ to 3‐week duration are potentially important in triggering and sustaining El Niño‐Southern Oscillation events. One such burst of 10‐day duration and maximum speeds of greater than 10 m s−1 occurred in May 1986 west of the date line. The response to this westerly wind burst is documented from equatorial current meter moorings, thermistor chain moorings, and sea level and hydrographic data. At 0°, 165°E in the western Pacific the thermocline was depressed by 25 m, sea surface temperature dropped by 0.3°–0.4°C, and sea level rose by 10–15 cm a few days after the maximum in westerly wind speed. Likewise, the South Equatorial Current rapidly accelerated eastward and attained speeds in excess of 100 cm s−1. Vertical shear in an approximately 100 m deep surface layer reversed within a few days of the winds, consistent with a simple model of equatorial mixed layer dynamics in which vertical eddy viscosities are inferred to be O(100 cm2 s−1). A sharp Kelvin wavelike pulse in sea level propagated out of the directly forced region into the central and eastern Pacific. The pulse took 45 days to travel from Tarawa (1°N, 173°E) to La Libertad (2°S, 81°W) on the South American coast, at an average phase speed of about 300 cm s−1. This is of the same order of magnitude as, but significantly higher than, the phase speed of a first baroclinic mode Kelvin wave and is probably the result of Doppler shifting by the Equatorial Undercurrent. A rise in sea surface temperature of about 1°C in 2 days occurred at 0°N, 110°W with the passage of the pulse. However, coincidental meridional advection of a sharp sea surface temperature front, rather than zonal advection of downwelling associated with the pulse, appears to be responsible for this warming. The relevance of this wind‐forced pulse to the subsequent evolution of the 1986–1987 El Niño‐Southern Oscillation event is discussed in the light of these observations.

This report describes sampling and error characteristics of self-siphoning rain gauges used on moored buoys designed and assembled at NOAA's Pacific Marine Environmental Laboratory (PMEL) for deployment in the tropical Pacific and Atlantic Oceans in support of climate studies. Self-siphoning rain gauges were chosen for use on these buoys because they can be calibrated at PMEL before and after deployment. The rainfall data are recorded at 1-min intervals, from which daily mean rate, standard deviation, and percent time raining are calculated and telemetered to PMEL in real time. At the end of the deployment, the 1-min, internally recorded data are recovered and processed to produce 10-min rain rates. Field data from a subset of these rain gauges are analyzed to determine data quality and noise levels. In addition, laboratory experiments are performed to assess gauge performance. The field data indicate that the noise level during periods of no rain is 0.3 mm h Ϫ1 for 1-min data, and 0.1 mm h Ϫ1 for 10-min data. The estimated error in the derived rain rates, based on the laboratory data, is 1.3 mm h Ϫ1 for 1-min data, and 0.4 mm h Ϫ1 for 10-min data. The error in the real-time daily rain rates is estimated to be at most 0.03 mm h Ϫ1. These error estimates do not take into account underestimates in accumulations due to effects of wind speed on catchment efficiency, which, though substantial, may be correctable. Estimated errors due to evaporation and sea spray, on the other hand, are found to be insignificant.

Surface measurements of precipitation in oceanic environments have proven especially difficult to obtain because traditional technologies such as tipping-bucket rain gauges are unsuitable for deployment from oceanic platforms such as ships and moorings. Recently, the Pacific Marine Environmental Laboratory of the National Oceanic and Atmospheric Administration has modified a collection gauge, the R. M. Young Company rain gauge, for long-term deployment on deep ocean moorings. This instrumentation package was deployed during part of the South China Sea Monsoon Experiment. Also deployed on the same mooring were two acoustic rain gauges (ARGs) that monitor precipitation through the interpretation of the high-frequency, from 500 to 50 000 Hz, underwater sound field. The mooring was located at 20Њ22.2ЈN, 116Њ31.2ЈE and was in place from 7 April-5 June 1998. Unfortunately, pirates stole the surface instrumentation on 6 May 1998, limiting data from the R. M. Young rain gauge to satellite transmissions prior to the attack. The ARGs survived the attack and reported data throughout the deployment. The acoustic data are interpreted to provide quantification of wind speed; detection, classification, and quantification of rainfall; and the detection and quantification of near-surface bubble layers. Percentage-of-time-raining data from the two rainfall measurements are in excellent agreement. Based on comparison with the R. M. Young rain gauge data, modified acoustic rainfall algorithms are proposed. The acoustic detection of several instances of high near-surface bubble injections during extremely heavy rainfall is described.

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