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H. A. Panofsky
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H. A. Panofsky
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H. A. Panofsky

Abstract

The theory of a number of different techniques for the computation of vertical motion in the atmosphere is discussed. A comparison of two independent techniques shows that both usually yield vertical velocities of the correct sign and order of magnitude.

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H. A. Panofsky

Abstract

Radiative cooling is computed for a warm, isothermal atmosphere streaming out over a cold surface. The study shows that the rate of cooling at heights from a few centimeters up to a few meters varies inversely as the square root of the distance from the ground, and that it varies somewhat more rapidly at larger distances.

The difference in radiative cooling at low levels between an isothermal and an adiabatic atmosphere is computed and found to be negligible in comparison with values derived from the isothermal atmosphere.

Comparison of radiative with observed cooling shows that radiative cooling is relatively small compared with cooling by turbulence in winds around 15 mph.

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H. A. Panofsky
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H. A. Panofsky
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L. Kristensen and H. A. Panofsky

Abstract

Standard deviations of wind direction fluctuations at 76 m at Risø for the first half year of 1975 have been analyzed as functions of wind speed and temperature lapse rate, either measured near the surface or near the level of the azimuth variations. Between 31 and 37% of the variance of the standard deviations (σA) is accounted for by the predictors. For strong winds, σA approaches a constant, about 3.5°. This is consistent with the value expected for overwater trajectories. For lower speeds, σA generally increases with decreasing hydrostatic stability. Largest values are found with weakest winds. In unstable air, σA always decreases with increasing wind speed. In stable air, there is a minimum σA for a particular wind speed. These properties are compared with a new theory of fluctuations of horizontal wind components.

An analysis of independent data (July–October, 1975) showed the same pattern but significantly higher values of σA with strong winds. This is presumably due to the fact that in this period a significantly larger fraction of air reached the tower after an overland trajectory.

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H. A. Panofsky and B. Prasad

Abstract

The Air Pollution Division of the State of Pennsylvania has conducted simultaneous measurements of meteorological variables and air quality at Johnstown, Pa. An analysis of the observations for two fall seasons showed that fluctuations in the concentrations can be fairly well explained by the changes in wind speed and fluctuations of vertical air velocities. Wind direction is relatively unimportant, except for the rare east winds, when the air at Johnstown is affected by a major steel plant.

This paper presents a simple mathematical model that predicts variations in air pollution from a large number of low-level sources in a narrow valley. This theory and observations are in good agreement. It is likely, therefore, that most of the pollution at Johnstown and similar sites is locally produced.

Due to the fact that there usually are no important high-stack sources upwind at Johnstown at present, fumigation is not generally a factor there.

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A. K. Blackadar and H. A. Panofsky
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Richard Lyons, H. A. Panofsky, and Sarah Wollaston

Abstract

It is shown that, in the lowest few hundred meters, nighttime inversions tend to break down due to onset of turbulence when the Richardson number falls between 0.2 and 0.5. Since the Richardson number is statistically related to the wind speed at one to a few hundred meters, it is found that the dew-point depression in the morning, as well as visibility, is related to the wind speed above the surface. It follows, that objective forecast techniques for the dew-point depression and visibility can be improved by including the wind speed above the surface as a parameter.

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