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  • Author or Editor: J. I. Katz x
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J. I. Katz

Abstract

The phenomenon called the subsun is the specular reflection of sunlight by horizontally oriented plates of ice. Although well known in meteorological optics, the hydrodynamics of the orientation is not quantitatively understood. The theory of torques on objects at low Reynolds numbers is reviewed; coefficients C o, C p, and C ψ that describe the orienting torques on discs, rods, and hexagonal prisms are defined; and the results of experiments to measure C o and C p are reported.

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J. D. Sartor, I. Katz, and R. E. Katz

Interest of the radio-meteorologist centers on diffusion because the vertical structure and the non-homogeneity of the atmosphere, in terms of refractive index, play a vital part in radar propagation. A portable method of measuring diffusion consists of lifting smoke-puff generators aloft with tethered balloons, setting off puffs remotely and photographing them with two motion picture cameras. From the resulting records of the areal spread of the smoke and the distance it travels, one may compute values of diffusion coefficients. Preliminary experiments yield data in accord with values published by Sutton.

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L. M. Canel and J. I. Katz

Abstract

Drawing from a NOAA database of hourly precipitation data from 5995 stations in the contiguous United States over the period 1949–2009, the authors investigate possible trends in the variance of the hourly precipitation, averaged over the diurnal and annual cycles and normalized by the square of the mean precipitation at that site. This normalized variance is a measure of storminess, distinct from increases in precipitation attributable to warming. For the 1722 stations surviving quality control with data on at least 80% of days in at least 30 years, the authors compute the rate of change of the logarithm of the normalized variance at each station and set bounds on its mean (over stations) trend. The logarithmic function weights the trends at calm stations equally to those at stormy stations and enhances the statistical power of the mean. The authors find a logarithmic rate of change of the mean normalized variance of yr−1 (). The upper bounds on any continentally averaged trend, increasing or decreasing, are about 0.001 yr−1 (doubling or halving times > 1000 years). It is found that the normalized variance in the Los Angeles basin has increased at a statistically significant rate. This may be attributable to a decrease in the number of aerosol condensation nuclei. Upper bounds are set on any effect of the 11-yr solar cycle.

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