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Hans A. Panofsky

Abstract

Monin-Obukhov scaling and convective scaling both apply over a range of heights z given approximately by −L<z<0.1zi where L is the Monin-Obukhov length and zi the height of the lowest inversion.

This region is defined here as the “convective matching layer”. From the matching conditions, special relations are derived between turbulence statistics, heat flux and height which turn out to be the same as relations previously derived by dimensional analysis in the “free-convection layer”. Thus the convective matching layer is the free-convection layer viewed from a different vantage point.

Expressions for the spectra of vertical velocity and temperature can be derived from matching conditions and the hypothesis that they consist of products of two functions, one of which describes the magnitude, the other the shape of the spectra.

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Large-Scale Vertical Motion and Weather in January, 1953

(Mineral Industries Contribution No. 56-32)

Albert Miller and Hans A. Panofsky

This paper summarizes the relationships between weather, moisture and large-scale vertical motion for January, 1953. The moisture parameter was the dew point depression at 850 mb, and vertical velocities at 700 mb were available as computed by three different methods. The probability of clear sky at an individual station varies from five percent for moist, ascending air to 93 percent for dry, descending air. The probability of precipitation for the same conditions varies from 67 percent to 0 percent.

Incidentally, comparison of vertical velocities of various types indicates that nonadiabatic warming at 700 mb is important only for rapid flow from north to south, then averaging 1.3C in 12 hours.

The standard errors of the different techniques of computing vertical motion are estimated to vary from 0.9 to 1.4 cm sec−1.

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Franz Fiedler and Hans A. Panofsky

The kinetic energy of the atmosphere is not spread uniformly over all wavelengths but has certain preferred scales, with gaps in between.

Typically atmospheric structures are either fully three dimensional with horizontal wavelengths of the order of 100 m to several kilometers, such as convection cells (including thunderstorms) and mechanically driven eddies; or they are quasi-two-dimensional with horizontal dimensions of order of thousands of km. The first group of systems derives its energy from Kelvin-Helmholtz and hydrostatic instability, which depends on vertical gradients of wind and temperature; the second group is associated with barotropic or baroclinic instability, which depends on horizontal gradients of temperature and wind.

Aloft, the small-scale systems are relatively less frequent than near the ground; on the other hand, intermediate-scale systems seem to be more common.

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Morris A. Bender, Hans A. Panofsky, and C. A. Peslen

Abstract

From the end of October 1973 to the beginning of January 1974, Continental Airlines operated one of its Boeing 747 aircraft with special instrumentation for the study of clear-air turbulence (CAT). The observations were compared with satellite-derived radiance gradients, conventional temperature gradients from analyzed maps, and temperature gradients obtained from a Rosemount total air temperature sensor on the plane. The results led to the following conclusions:

1) In regions of weak gradients of temperature or of CO2 band radiance, the probability of CAT is extremely small.

2) CAT probabilities are significantly higher over mountains than flat terrain.

3) Even over mountains the probability of CAT is greatly increased by large gradients of temperature or radiance.

4) Satellite radiance gradients appear to discriminate between CAT and no CAT better than conventional temperature gradients over flat lands, whereas the reverse is true over mountains—although the differences between the two techniques are not large over mountains. Since most of the flights over flat terrain were flown over the Pacific Ocean, the result, if significant, may suggest that conventional temperature gradients over regions of sparse data are not as accurate as temperature gradients which can be inferred from satellites.

5) Temperature gradients obtainable from aircraft temperature sensors are not correlated with CAT statistics.

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John F. Pohle, Alfred K. Blackadar, and Hans A. Panofsky

Abstract

No abstract available.

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PAUL R. JULIAN, LOWELL KRAWITZ, and HANS A. PANOFSKY

Abstract

The flow at 500 mb. is compared with that at 100 mb. With the exception of the polar vortex, the patterns at the two levels tend to show a distinct similarity, with the major exception that small-scale features at 500 mb. are not present at 100 mb.

In middle latitudes, the wind speeds at the two levels are of the same order of magnitude, with a systematic excess of the 100-mb. speeds over the 500-mb. speeds at latitudes 30° and farther south.

In the region of the polar vortex, heights at the two levels are still well correlated. Variations in height over long periods tend to be much larger at 100 mb. than at 500 mb. Similarly, the winds at 100 mb. are much stronger than those at 500 mb.

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Douglas M. Carl, Terry C. Tarbell, and Hans A. Panofsky

Abstract

Wind and temperature Profiles from three towers were examined under conditions of fairly homogeneous fetch. With numerically small Richardson numbers, no significant deviations from logarithmic profiles were detected up to 150 m.

Under non-neutral conditions, Monin-Obukhov scaling described the profiles well, provided that surface values of the scaling parameters were used.

Nondimensional wind profiles in stable air agree well with corresponding profiles in the surface layer. In unstable air the nondimensional functions deviated slightly from the functions found near the ground. In particular, for large |z/L|, ϕm approached |z/L|&minus½ rather than |z/L|−¼

Nondimensional temperature profiles showed some systematic differences from the corresponding profiles near the ground. In a few cases the lapse rate reversed above some height, so that the normalized temperature gradient became negative.

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Hans A. Panofsky, John A. Dutton, Kurt H. Hemmerich, G. McCreary, and N. V. Loving

Abstract

Two separate case studies of clear air turbulence are presented, one in the stratosphere over the Rocky Mountains, the other in the upper troposphere over the midwestern plains.

The mechanism in both situations appears to be similar. CAT occurs in strongly baroclinic zones with strong vertical wind shears and low Richardson numbers. There is a tendency for the most severe turbulence to be located at the edges of the baroclinic zones.

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Michael D. Fromm, Lanning M. Penn, John J. Cahir, and Hans A. Panofsky

Abstract

Multiple linear regression is used to relate monthly means and year-to-year changes of the monthly mean planetary albedo and infrared flux leaving the atmosphere, as measured by NOAA satellites, to certain meteorological quantities. Physical predictors are selected which are likely to influence cloudiness, such as temperature, relative humidity and wind. Such predictors can be readily obtained from numerical models.

Forty-two months of polar orbiter measurements of radiation fluxes and objective analyses from NMC's operational model were related. Continental and oceanic samples were evaluated separately. Checks on the model consisted of independent tests and comparison with estimation of radiation fluxes in which predictors were functions of latitude, longitude and time of year only. Physical predictors are consistently superior, with the single exception of oceanic albedo, where there was little difference.

In the case of the infrared flux, 93 and 84% of the variance in the monthly means is explained over land and ocean, respectively. The Planck function computed from a humidity (cloud) sensitive radiating temperature is the dominant predictor, with other humidity predictors also useful. Between 60 and 72% of the variance of the albedo is explained; results over land again are superior. Relative humidity and midtropospheric wind speed variables dominate in this case. Greater success with infrared is probably attributable to a failure to adequately estimate the effect of low-topped clouds, which impact the albedo differentially. Over land, patterns of year-to-year changes of visible and infrared fluxes (surrogates for anomalies) are predicted well and are consistent with observed changes in rainfall and cloudiness. Over the means the skill for year-to-year changes is low, possibly because low-topped clouds are more common, but also because analyses are poorer there.

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Steven G. Perry, John M. Norman, Hans A. Panofsky, and J. David Martsolf

Abstract

A surface layer experiment is described which includes measurements of turbulent velocities at 2 m above the surface with an army of newly developed drag anemometers. The experiment site is located in central Pennsylvania where mesoscale topographic irregularities exist. The presence of a low mountain ridge near the site affects the estimated lateral scale of turbulence and the fluctuations of the lateral velocity component. A good correlation has been found between the variance spectrum of the lateral (or crosswind) velocity component and an estimate of the lateral Eulerian integral scale of the longitudinal velocity component. This can provide future estimates of the lateral scale from turbulent velocity measurements at a single location.

A model for the decay of horizontal coherence which accounts for the stability, roughness and instrument separation has been suggested in a previous paper by Panofsky and Mizuno. The present data compare favorably with this model. The effect of stability on coherence decay is found to have a definite site dependence.

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