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HOMER T. MANTIS

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Homer T. Mantis

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Homer T. Mantis

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Spectra of the variance of horizontal velocities derived from the trajectories of superpressure altitude-controlled balloons have been obtained in the frequency range 0.005 to 0.5 cy min−1. With the aid of other constant-altitude balloon data, a spectrum of velocity variance of the upper tropospheric winds is proposed for a range of frequencies termed mesoscale, which is meant to describe scales of motion just smaller than synoptic scale but larger than the motions usually referred to as turbulence. The mesoscale spectra all decreases sharply with frequency at frequencies just above synoptic scale to a frequency of about 0.1 cy min−1, where an irregular increase sets in. The spectra continue to rise to the highest frequencies analyzed, pointing to a second spectral maximum in the turbulent regime. The spectra have been used to estimate the non-representative mesoscale standard deviation of the upper winds of 7 to 17 knots. A horizontal diffusivity by mesoscale motions is estimated to be of the order of 102 cm2 see−1.

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Homer T. Mantis
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Homer T. Mantis

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James E. Miller and Homer T. Mantis

An objective method of forecasting visibility at La Guardia Field, N. Y., in the winter season, is developed from data for the winter of 1943–44 and tested in the winter of 1944–45. The method is based on 24-hr air trajectories, which are forecasted by a carefully prescribed, routine procedure. The visibility at the origin of a trajectory, the location of the origin, and the final wind velocity implied by the last segment of the trajectory, are combined by means of forecast charts and a formula, to produce a 24-hr forecast of the visibility. Tests of the method show that its accuracy is not much different from the accuracy of visibility forecasts for La Guardia by other methods, but it is pointed out that an objective procedure has certain advantages over the normal subjective forecasting methods.

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James E. Miller and Homer T. Mantis

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A total of 222 extratropical cyclones originating in the Pacific coastal region of Asia in the months October through April from 1932 to 1937 are summarized according to the following characteristics: geographical and monthly frequency; relation of frequency to topography; 24-hour displacement; and relation of displacement to topography. Some of the characteristics of Asiatic cyclones are compared with the characteristics of cyclones forming along the North American east coast.

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Homer T. Mantis, Christos C. Repapis, Christos S. Zerefos, and John C. Ziomas

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The average areal density of pollutant emissions in Athens is estimated to be two to six times greater than in the Los Angeles basin. Concentration levels of the primary air pollutants, CO and SO2, are several times larger in Athens than in Los Angeles. Concentrations of the photochemical pollutants, NO2 and O3, however, are greater at Los Angeles stations inland 20 or more kilometers from the coast. The relatively lower levels of photochemical pollution in Athens are partially explained by differences in the summer atmospheric-circulation systems and the scale of the basins. Also, the concentration of NO in central Athens is so great as to inhibit the formation of O3.

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