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Richard E. Payne

Abstract

A new meteorological sensing, recording, and telemetering package based on digital data processing techniques has been developed for long-term (6-month) deployments on surface buoys moored in the ocean. Data are recorded on magnetic cassette tapes and telemetered via satellite and Service Argos. Sensors for measuring vector-averaged wind speed and direction, air and water temperature relative humidity, solar radiation, and barometric pressure were selected for accuracy and reliability. Except for relative humidity, performance of the sensors has been excellent. Results of ship-to-buoy comparisons of wind speed and air temperature sensors show agreement within the basic ship sensor accuracies, i.e., 0.1 m s−1 and 0.4°C.

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Richard E. Payne

Abstract

A variety of Pressure sensors have been tested in the laboratory for accuracy and long-term stability. The Paroscientific 215-AT, Rosemount 1201 FIB, and Setra 270 were found to be the most accurate, maintaining 0.1-mb accuracy over long periods. These were followed by the AIR DB-1A with 0.5 mb in most units tested. The Paroscientific and AIR sensors require the least power and are the most suitable for remote deployments. Results on several inexpensive sensors show that some are worthy of consideration if accuracy requirements can be relaxed somewhat. The AIR DB-1A was selected for use in the barometric pressure module for the IMET (improved meteorology) system.

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Richard E. Payne and Steven P. Anderson

Abstract

For some years, investigators have made measurements of downwelling longwave irradiance with the Eppley Precision Infrared Radiometer (PIR), recording the values of thermopile voltage and body and dome thermistor resistances and combining them in data processing. Part I of this paper reviews previous work on the processing equation and presents an improved equation. It establishes that the standard single-output Eppley has an inherent uncertainty of 5%. By measuring the three possible outputs separately and comparing them in the improved equation, the inherent accuracy can be improved to 1.5%. Part II presents a method of calibrating the Eppley PIR for the three-output equation using an easily constructed blackbody cavity in a temperature bath capable of a 0°–50°C temperature range. Calibration of PIR thermistors is recommended since occasionally one is found out of specifications.

An outdoor comparison of 15 PIRs calibrated with the technique was carried out in groups of four, with one PIR used in all of the groups as a standard of comparison. The mean differences and 1-min standard deviations between 12 individual PIRs and this standard over comparison periods of 10–22 days were less than 6.0 and 11 W m−2, respectively. Only two of the PIRs and a standard single-output Eppley PIR (calibrated by Eppley) had mean differences and standard deviations greater than 7 and 11 W m−2, respectively. Although the new calibration procedure yielded consistent results in the mean, at times the longwave measurements diverged by up to 45 W m−2 for several hours. Some of these events are attributable to confirmed pinholes in the dome filter, but others are left unexplained.

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David S. Hosom, Robert A. Weller, Richard E. Payne, and Kenneth E. Prada

Abstract

The recently developed IMET (improved meteorology) system for ships and buoys and the key elements of the program that led to its development are described. The system improves the ability to measure mean meteorological variables, including wind velocity, barometric pressure, incoming shortwave and longwave radiation, air temperature, sea surface temperature, humidity, and precipitation, from both types of platforms. Extensive laboratory and field tests of a variety of sensors were conducted to investigate and document their stability, accuracy, and reliability. Modular electronics were developed so that each sensor in the system communicated digitally, returning calibrated values to a central data recorder. IMET systems have been deployed on buoys in the Atlantic and Pacific Oceans and on research vessels. The history of the program, reasons for the choice of the present sensor suite, the design of the sensor modules, a description of the data acquisition system, and examples of data collected with the system are described. A discussion of the areas in which further improvements to the system will be sought is also provided.

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Robert A. Weller, Daniel L. Rudnick, Richard E. Payne, Jerome P. Dean, Nancy J. Pennington, and Richard P. Trask

Abstract

An array of five surface moorings was set in the subtropical convergence zone southwest of Bermuda with spacings of 16 to 53 km. Meteorological instrumentation on each of the surface buoys recorded wind velocity, barometric pressure, solar radiation, air temperature, sea temperature, and relative humidity. One objective of the deployment was to look for horizontal variability in the meteorological fields on the scale of the array. In support of that objective, both a high data return from the instruments and a quantitative evaluation of the quality of the measurements were sought. To maximize data return rates, two meteorological instruments were placed on each buoy. To determine the accuracy of the measurements, careful predeployment and post-deployment calibrations of all instruments were carried out, and, during the experiment, meteorological data were collected from ships stationed near the buoys. From the two redundant instruments it was possible to construct one complete dataset for each mooring. The results of the calibrations and intercomparisons provided estimates of the errors in the measurements. Significant horizontal variability was occasionally observed in some of the surface meteorological variables and in the wind stress and air-sea heat flux fields. More often, observed spatial gradients in the meteorological fields were not significantly larger than the experimental uncertainty in those gradients. Larger than anticipated errors were encountered in measuring wind speed and barometric pressure, and the preformance of anemometers, barometers, relative humidity sensors, and other sensors for use on buoys could be improved.

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