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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

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Richard E. Payne

Abstract

An experimental study of the albedo of the sea surface for shortwave solar radiation has been carried out on a fixed platform. Fifteen-minute totals of upward and downward irradiances were recorded continuously for four months over a wide range of atmospheric and sea conditions. The resulting albedo values, the ratio of upward to downward irradiance, are expressed in terms of a particularly convenient pair of parameters, sun altitude and atmospheric transmittance (T). The latter is defined as the ratio of observed downward irradiance to the irradiance at the top of the atmosphere and has not been used before in describing albedo. Examples of albedo values are 0.061±0.005 for heavily overcast skies (0.0<T≤0.1), indicating isotropic radiance distribution, and a range for clear skies (T>0.65) of 0.03 for high sun to as large as 0.45 at sun altitudes <10°. The uncertainty in the values is less than 7% for sun altitudes >25° and increases to 25% for very low sun attitudes. The effect of wind, through surface roughness, is shown to be small but predictable. Effects of whitecaps are not noticeable at wind speeds up to 30 kt, the highest observed in the study.

Application of the results is made to climatological studies of the absorption of solar energy by the surface waters of the ocean. Monthly average albedos, are calculated for the Atlantic Ocean to compare with Budyko’s latitudinally dependent values, and it is shown that although the sets of results agree within 10% at latitudes up to 40°, there are discrepancies at higher latitudes as high as 100%. Finally it is shown with climatological albedo values calculated from the results of this study, that the accuracy of climatological estimates of solar energy absorbed in the ocean are now limited by the accuracy of climatological estimates of downward irradiance.

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Richard E. Payne and Steven P. Anderson

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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 M. Thompson Jr., Steven W. Payne, Ernest E. Recker, and Richard J. Reed

Abstract

Data from a dense network of ship observations are used to study the structure and properties of westward-moving wave disturbances observed in the eastern Atlantic Intertropical Convergence Zone (ITCZ) during Phase III of the GAPP Atlantic Tropical Experiment (GATE). Comparisons are made with similar disturbances found in the ITCZ of the western Pacific. Wave fields are determined by fitting low-order polynomials to the ship data with use of the method of least squares.

The wave structures in the two regions are found to be similar in many respects, the principal difference being in the divergence field and associated vertical motion. Unlike in the Pacific a multi-layer divergence pattern exists in the eastern Atlantic, leading us to hypothesize the existence of three main cloud populations with outflow levels near 800, 500 and 250 mb. The soundings for the Atlantic exhibit lesser parcel instability then the Pacific soundings in agreement with the reduced vigor of the convective cells and the greater tendency for multiple cloud layers. The strongest upward motion (∼150 mb day−1) occurs in and somewhat ahead of the wave trough, as in the Pacific, but at a much lower level (800–700 mb). A secondary maximum appears near 350 mb, where the primary maximum appears in the Pacific. The maximum precipitation rate of 22 mm day−1 is observed in the region of strongest upward motion. The rate decreases to 4 mm day−1 in the region of suppressed convection near the wave ridge. Vertical eddy flux of total heat is largest at the 800 mb level in the wave trough (225 W m−2) and produces cumulus heating and cooling of about 5°C day−1 above and below the maximum, respectively.

A nearly balanced moisture budget for the inner ship array or B-scale area was obtained from the fitted fields when data from both outer and inner ships were employed in the fitting. In particular, two individual waves and the composite or average wave yielded sufficiently accurate budgets to encourage their use in quantitative studies of interactions between synoptic-scale and convective-scale systems. The residual in the heat budget suggests a radiational cooling rate of 0.9°C day−1. The surface energy budget indicates a net radiative flux at the surface of 129 W m−2 of which 106 W m−2 was used for evaporation and 12 W m−2 for sensible heat flux to the atmosphere, leaving 11 W m−2 for heating of the ocean mixed layer. The heat exchange between ocean and atmosphere underwent a pronounced variation with passage of the synoptic disturbances, causing sea surface temperatures to be 0.3°C warmer ahead of the wave troughs than behind. Precipitation rates employed in the budgets were based on radar measurements; surface sensible and latent heat fluxes were computed by the bulk aerodynamic method with use of temperatures, humidities and winds from the booms of four B-scale ships; and net radiation at the surface was obtained from measurements made aboard the same four ships.

The kinetic energy of the waves was provided by the barotropic conversion process (conversion from zonal kinetic energy), the baroclinic conversion being negative and thus a sink for the eddy kinetic energy. Likewise, the generation of eddy available potential energy was negative, implying that latent heat release opposed, rather than contributed, to the wave growth. The described conditions are quite unlike those in the western Pacific ITCZ where condensation heating provides the source for the wave energy and the barotropic conversion constitutes a weak sink.

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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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Suzanne Van Cooten, Kevin E. Kelleher, Kenneth Howard, Jian Zhang, Jonathan J. Gourley, John S. Kain, Kodi Nemunaitis-Monroe, Zac Flamig, Heather Moser, Ami Arthur, Carrie Langston, Randall Kolar, Yang Hong, Kendra Dresback, Evan Tromble, Humberto Vergara, Richard A Luettich Jr., Brian Blanton, Howard Lander, Ken Galluppi, Jessica Proud Losego, Cheryl Ann Blain, Jack Thigpen, Katie Mosher, Darin Figurskey, Michael Moneypenny, Jonathan Blaes, Jeff Orrock, Rich Bandy, Carin Goodall, John G. W. Kelley, Jason Greenlaw, Micah Wengren, Dave Eslinger, Jeff Payne, Geno Olmi, John Feldt, John Schmidt, Todd Hamill, Robert Bacon, Robert Stickney, and Lundie Spence

The objective of the Coastal and Inland Flooding Observation and Warning (CI-FLOW) project is to prototype new hydrometeorologic techniques to address a critical NOAA service gap: routine total water level predictions for tidally influenced watersheds. Since February 2000, the project has focused on developing a coupled modeling system to accurately account for water at all locations in a coastal watershed by exchanging data between atmospheric, hydrologic, and hydrodynamic models. These simulations account for the quantity of water associated with waves, tides, storm surge, rivers, and rainfall, including interactions at the tidal/surge interface.

Within this project, CI-FLOW addresses the following goals: i) apply advanced weather and oceanographic monitoring and prediction techniques to the coastal environment; ii) prototype an automated hydrometeorologic data collection and prediction system; iii) facilitate interdisciplinary and multiorganizational collaborations; and iv) enhance techniques and technologies that improve actionable hydrologic/hydrodynamic information to reduce the impacts of coastal flooding. Results are presented for Hurricane Isabel (2003), Hurricane Earl (2010), and Tropical Storm Nicole (2010) for the Tar–Pamlico and Neuse River basins of North Carolina. This area was chosen, in part, because of the tremendous damage inflicted by Hurricanes Dennis and Floyd (1999). The vision is to transition CI-FLOW research findings and technologies to other U.S. coastal watersheds.

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