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Fred V. Brock

Abstract

An analog computer has been programmed to process anemometer-bivane data recorded on magnetic tape. The recorded data were the wind vector in spherical coordinates, azimuth angle, elevation angle and wind speed. The computer resolved this vector into rectangular coordinates and computed continuous averages of the means and standard deviations of each of the three components in one pass. Over 1600 hours of data were processed at 64 times real time. This time compression was achieved by recording the data at 15/16 inches per second and playing it back at 60 inches per second.

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Fred V. Brock

Abstract

The partial differential equation which describes steady-state diffusion from an infinite line source is replaced with a set of simultaneous ordinary differential equations solved on an electronic analog computer. One space dimension, distance downwind, is represented by computer time; the other, height, is replaced with finite differences. Solutions are obtained for constant, power law, and logarithmic wind profiles, and for diffusion of particulates which can settle out and deposit on the ground.

All solutions are obtained with one basic computing circuit. Each problem requires only a particular setting of the coefficient potentiometers in the circuit. Implementation of this circuit requires only 9 integrating amplifiers and 26 coefficient potentiometers, available in any medium sized computer.

The solution's accuracy has been measured by comparing the computer plots with the analytical solution for constant wind profile. This measures the total error due to the finite difference approximation and to computer errors. The solution's accuracy is found to be 5 per cent or better over most of the field.

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Fred V. Brock

Concrete pavement may be adversely affected by weather and climate through the freezing process either within or under the pavement. The common results of freezing action that are detrimental to the durability and usefulness of the pavement are differential frost heave, loss of subsoil bearing strength, migration of subsoil, loss of strength of the concrete itself, and scaling of the pavement surface. Temperature and moisture are the dominant factors in each of these effects.

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Fred V. Brock

Abstract

Nonlinear median filters were modified to use threshold logic and used to remove impulse noise (spikes) from a set of meteorological data. The impulse noise in the dataset, which originated in the communications section of the Portable Automated Mesonet, could be characterized as random bit noise. Most of the pulses had a duration of one time interval, which in this case was one minute. The filters were effective irrespective of the frequency of occurrence and of the amplitude of the noise spikes. Pulses were removed even when the frequency of occurrence rose to every other data point as was observed in several short intervals. The amplitude of pulses removed ranged over three orders of magnitude.

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E. Wendell Hewson and Fred V. Brock

A hybrid analog-digital computer has been established in the Department of Meteorology and Oceanography of the University of Michigan. It comprises three medium size analog computers, a small, general purpose digital computer, and an analog/digital linkage so that all of the computers can be operated together as a hybrid system.

The primary functions of the computer are acquisition and reduction of field data and research in meteorological simulation. It is capable of accepting data acquired on-line from local instruments, or recorded in the field on analog magnetic tape, digital magnetic tape or punched paper tape. These data can then be processed in either analog or digital form or transmitted to a large digital computer via magnetic tape.

The analog computers are versatile and of sufficient capacity to be useful for many analog data processing tasks as well as for simulation of atmospheric models such as those used in the study of diffusion and micrometeorology.

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Fred V. Brock and E. Wendell Hewson

Abstract

The analog computer has been used to obtain solutions to the diffusion equation for the case of a continuous point source aloft. The basic model used is that of a source located between an inversion and the ground where the wind speed and eddy diffusivity are constant over the diffusing region. Solutions were also obtained with several special features added to the basic model: representation of the eddy diffusivity as a function of distance downstream; presence of wind direction shear in the diffusing layers; and the presence of large-scale eddies which cause the meandering of the plume.

The solutions are presented as deviations from the reference solution, that solution derived from the basic model, to show graphically the effects of each parameter change.

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Fred V. Brock and Daniel J. Provine

Abstract

The standard deviation computer is a small electronic analog device which is designed to calculate the standard deviation of a voltage signal with less than 5 per cent error. The output is a continuous voltage signal proportional to the standard deviation which is generated with a computation time equal to the sampling period. Mathematically, this instrument computes the mean absolute deviation which is related to the standard deviation by a constant factor. It accepts signals in the frequency range of from d-c to some upper limit determined by amplifier bandwidth over a wide range of amplitudes and computes with sampling times up to 3600 seconds or more. In field tests, the computer operated successfully on the output of a wind vane.

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Fred V. Brock, George H. Saum, and Steven R. Semmer

Abstract

The Portable Automated Mesonet II (PAM II) system was developed by NCAR to provide surface mesoscale data for the research needs of the atmospheric science community. The PAM system has 60 remote stations with planned growth to 300. In such a distributed system, data communication is a vital subsystem and, since it dictates some key system constraints, deserves special attention. The NOAA/NESDIS satellite, GOES, is used to link the remote stations to the base stations. This provides very wide areas coverage but limits the data rate.

Special attention was given to the design of the sensor subsystems to minimize the possibility for human error and to maintain the calibration in field conditions while using interchangeable modules. This was achieved by using a dedicated microprocessor in the psychrometer and the barometer. The microprocessor in the sensor modules controls the sensors, applies the individual calibration coefficients, and transmits the sensor data to the master data acquisition module.

The master base station collects the data, archives them and generates graphic displays of real-time or archived data for system control and scientific analysis. The field base stations provide real-time data for the user in the field environment.

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Scott J. Richardson, Fred V. Brock, Steven R. Semmer, and Cathy Jirak

Abstract

Multiplate radiation shield errors are examined using the following techniques: 1) ray tracing analysis, 2) wind tunnel experiments, 3) numerical flow simulations, and 4) field testing. The authors’ objectives are to develop guidelines for radiation shield and temperature sensor design, to build an improved shield, and to determine factors that influence radiational heating errors. Guidelines for reducing radiational heating errors are given that are based on knowledge of the temperature sensor to be used, with the shield chosen to match the sensor design.

A new class of shield called a part-time aspirated multiplate radiation shield is introduced. This type of shield consists of a multiplate design usually operated in a passive manner but equipped with fan-forced aspiration capability to be used when necessary (e.g., low wind speed). A prototype shield reduced radiational heating errors from 2° to 1.2°C. In addition, nighttime low wind speed errors were reduced from 1.6° to 0.3°C. Existing passive shields may be modified to incorporate part-time aspiration, thus making them cost effective.

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Fred V. Brock, Kenneth C. Crawford, Ronald L. Elliott, Gerrit W. Cuperus, Steven J. Stadler, Howard L. Johnson, and Michael D. Eilts

Abstract

The Oklahoma mesonet is a joint project of Oklahoma State University and the University of Oklahoma. It is an automated network of 108 stations covering the state of Oklahoma. Each station measures air temperature, humidity, barometric pressure, wind speed and direction, rainfall, solar radiation, and soil temperatures. Each station transmits a data message every 15 min via a radio link to the nearest terminal of the Oklahoma Law Enforcement Telecommunications System that relays it to a central site in Norman, Oklahoma. The data message comprises three 5-min averages of most data (and one 15-min average of soil temperatures). The central site ingests the data, runs some quality assurance tests, archives the data, and disseminates it in real time to a broad community of users, primarily through a computerized bulletin board system. This manuscript provides a technical description of the Oklahoma mesonet including a complete description of the instrumentation. Sensor inaccuracy, resolution, height with respect to ground level, and method of exposure are discussed.

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