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W. E. Bardsley

Abstract

The largest hailstone to strike a hailpad is often smaller than the largest hailstone observed in the immediate vicinity. This has given rise to some comment in the literature, but the apparent anomaly is only a trivial consequence of the observation process. However, relationships between these two types of maxima can be utilized via extreme value theory to make inferences concerning the largest hailstones beyond the immediate observation area.

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W. E. Bardsley

Abstract

The inverse Gaussian distribution is suggested as an alternative to the three-parameter Weibull distribution for the description of wind speed data with low frequencies of low speeds. A comparison of the two distributions indicates a region of strong similarity, corresponding reasonably well to three-parameter Weibull distributions which have been fitted to wind data.

Maximum likelihood estimation of the inverse Gaussian parameters is much simpler than the iterative technique required for the three-parameter Weibull distribution. In addition, the inverse Gaussian distribution features the mean wind speed as a parameter, a desirable property for wind energy investigations. A summation-reproductive property of the distribution permits estimation of the mean wind energy flux from a sequence of speed averages.

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W. E. Bardsley and M. M. Khatep

Abstract

Asymptotic extreme-value theory is used as the basis of a stochastic model which predicts aspects of the freezing behavior of supercooled water droplets. The model gives a general theoretical base to an earlier empirical function relating droplet volume to droplet freezing temperature. At the same time, the model indicates that the established empirical relation is only one of three possible functions linking droplet volume and temperature of freezing.

The free functions arise as a consequence of three possible extreme-value distributions of droplet freezing temperatures, and the form of each function predicts the type and parameter values of the distributions concerned. The proposed model is amenable to rigorous experimental verification since both the distribution type and parameter values can be estimated independently from droplet freezing data.

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W. E. Bardsley and B. F. J. Manly

Abstract

Regression-based estimators are presented for the long-term mean and variance of wind speed at a potential aerogenerator site. By “long term” is meant the mean and variance of wind speed which would have been obtained from the site if recordings had been made during the (long) period of record of some more distant recording station. The estimators make allowance for the sampling errors of regression parameters, permitting application to the typically small amounts of data available at aerogenerator sites.

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M. M. Khatep, B. B. Fitzharris, and W. E. Bardsley

Abstract

The mean water vapor transfer of the Southwest Pacific, as determined from radiosonde records near the 170°E meridional transect, is computed for the 1960–73 period. Emphasis is placed on defining average patterns, then examining variations that arise during the wettest and driest years and seasons in New Zealand over that period. Over the midlatitudes, the mean transfer is predominantly from the west, and most developed in summer. Over the subtropics, the mean summer transfer is predominantly from the north or northeast, but in winter a northwest flow prevails. Patterns of water vapor transfer during wet and dry periods over New Zealand differ more in direction than in magnitude, with the subtropical easterlies extending farther poleward during wet periods, especially in summer.

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