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Stanley Q. Kidder
and
Oskar M. Essenwanger

Abstract

The urban warming effect is interesting in its own right and is important for understanding global warming. The aim of this study is to determine how the urban warming effect changes with cloud conditions and with wind speed. Studies of the urban warming effect have mostly concentrated on the urban–rural difference in daily maximum or minimum temperatures. The problem was approached using a new technique. Instead of comparing a city, represented by a first-order weather station, with the surrounding rural area, represented by data collected by cooperative observers; pairs of cities, each with a first-order weather station, were studied. One city was large. The other city was small enough to have a minimal warming effect and was close enough to the larger city to approximately represent the rural area. In this way, hourly temperatures, cloud cover, and wind data could be studied rather than only the differences between the daily maxima or minima. Results show that wind disrupts the normal nocturnal cooling pattern in which the smaller city, with lower thermal inertia, cools more quickly than the larger city. Clouds also disrupt this pattern, at least to the extent that one must be careful about extrapolating either magnitudes or patterns of urban–rural temperature difference observed by satellites under clear sky conditions to partly cloudy or cloudy conditions.

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Dorathy A. Stewart
and
Oskar M. Essenwanger

Abstract

No abstract available.

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Dorathy A. Stewart
and
Oskar M. Essenwanger

Abstract

The purpose of this paper is to provide information about frequency distributions of wind speed near the surface of the earth. There has been a recent increased interest in this topic because of the potential for obtaining electrical energy from wind power.

Frequency distributions of wind speed from a large collection of data are examined. Most distributions are skewed to the right and the mean is usually greater than the median. Experience has shown that the Weibull distribution provides a good analytical approximation to the cumulative distribution and is particularly useful for the 90–99% thresholds. Two methods of fitting a Weibull distribution with a nonzero location parameter are discussed. Both of these methods require less computational effort than the maximum likelihood solution for a three-parameter model and are suitable for practical use by the engineer. It is shown that the three-parameter model is better than the two-parameter model for predicting extreme values.

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OSKAR M. ESSENWANGER
,
ROBERT E. BRADFORD
, and
WILLIAM W. VAUGHAN

Abstract

The existence of undetected errors in recorded wind observations may have a biasing influence on a statistical study. In the progress of some studies it has been found necessary to reexamine the data being used. A series of upper-air winds has been checked by using available listings of vertical shear and extreme winds. The developed procedure permits correction for major errors and tolerates the minor (random) errors.

The test of data by maximum wind profiles uses the highest and second highest scalar wind speed for each station and checks the data by profile scan. The test of data by vertical wind shear uses a critical value, theoretically derived, exceedance of which marks the data as suspicious. A detailed check of the wind observation verifies this suspicious value or it is corrected. In this program 3.5 percent of the observations proved suspicious and 85 percent thereof, that is, 2.9 percent of the observations, required correction. Thus the critical value is highly efficient.

The errors were traced and split into clerical errors (1.1 percent), instrumental errors (1.3 percent), and computational errors (0.5 percent), which are quite within reasonable limits.

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