ALBERT

Beschreibung: Measurements on rainfall near Hilo, Hawaii are described. Quartile deviations of drop-size distributions are plotted versus rainfall intensity. Comparison is made with similar data of Laws and Parsons, and certain similarities and differences are pointed out.

Beschreibung: A method is proposed for analyzing the effects of upper winds and terminal weather conditions on flight schedules. An analysis is presented for the 10,000-foot flight level along a given air route for the month of February. General conclusions including a comparison with other levels are presented and the methodology is discussed in detail.

Beschreibung: Various special methods of analyzing raobs in the tropics for forecasting purposes are tested and a combination of the best features found is recommended; this technique consists in plotting the 24-hour change of contours of the isobaric surfaces on a time or space cross-section. Some of the difficulties and limitations of such methods are pointed out.

Beschreibung: The purpose of presenting the following diagrams and cloud photos made in connection with an airplane flight over and through a cold front is to show cloud formations associated with a weak cold front. Such information is lacking in textbooks where only the more severe cold fronts are portrayed. Over land the front here described was preceded by daytime cumulus, their tops rising as the front approached. Some pileus was observed above them where later on Ac cumulogenitus (cug) formed as the tops reached that level. The layer became solid over the position of the cold front at the surface, and there was an upward bulge into the temperature inversion found at 8,000 feet. Over the sea, remains of the Ac cug in the form of lenticulars were found farthest ahead of the front. It is important to note that all the clouds were found some distance above the frontal discontinuity, within the warm air. This was owing to the dryness of the warm air. Detailed observations from the surface were made at Blue Hill Observatory, near by, during the flight.

Beschreibung: The basic laboratory experiment in which a supercooled cloud may be seeded and converted to ice crystals is described in considerable detail. Such information is given as type and preparation of the cold chamber, light sources which are effective for different purposes, methods to follow in forming supercooled clouds, and procedures to follow in seeding them. The transition temperature at which ice crystals form spontaneously is given as − 39°C ± 0.1°C as the result of a recent study. A simple replica technique for preserving the exact structure of the crystals in plastic is described.

Beschreibung: The article analyzes critically all cases of striped cirrus seen at Manila during the author's second Cloud Year, March 16th, 1946 to March 15th, 1947. The data favor the following conclusions: (a) Striped cirrus usually arise from the so-called false cirrus tops of cumulonimbus, strung out into lines by a strong upper air stream, (b) Striped cirrus at Manila are usually of forecasting value only if the typhoon or depression is to Manila's E-SE and the storm is moving W–WNW. (c) Great prudence should attend their use, since they may arise from any types of frontal or orographic disturbances apart from any typhoon whatsoever.

Beschreibung: Measurements of the upward and downward components of solar radiation were measured from a B-29 airplane on March 22, 1947. From these the albedo of the ground has been calculated. In the center of the country along the 39th parallel of latitude, the albedo of the ground, except when covered in part by snow, was found to be between .07 and .10. As the Western Mountains were approached, the albedo increased to .12. In the mountains, where the color of the terrain varies rapidly, the albedo reached a high value of .23, and averaged about .17. For terrain which was partially snow-covered the highest albedo measured was .29. Computations were made which showed the absorption of solar radiation to be about .06 ly/min in a unit column reaching from the ground to 10,000 feet which by itself would cause a temperature rise of .05C°/hr. in a cloudless smoky atmosphere.

Beschreibung: The rate of heat removal from the human body by wind and low temperature was termed Wind Chill by Siple and expressed by an empirical formula. This paper discusses the formula critically, pointing out that this measure of the convective heat loss may be less than three-quarters of the total heat lost by the body. Siple's formula is compared with those of others, and the use of the formula is discussed.

Beschreibung: Thermistor beads are used as the sensitive elements for measuring temperature and wind speed. Their high resistance makes it unnecessary to correct for the resistance of leads or the change in their resistance due to temperature. Because of the high negative temperature coefficient of resistance of thermistor material slight changes in ambient temperatures caused sufficient changes in the bead resistance to unbalance a bridge circuit and thereby activate a recording milliammeter which had been calibrated to read temperatures. The change in resistance of a hot bead by the wind activated a second milliammeter which was calibrated to read wind speed.

Beschreibung: To determine tentatively whether rain from cumulus clouds could be induced in temperatures above freezing, 15 tests totalling 54 seedings were made with dry ice. In 20 of these rain or virga was observed to come from the seeded cloud, and generally in less than 16 minutes after seeding. In one case, as much as 1.25 inches of rain fell from the seeded cloud. Cloud thickness is a significant factor distinguishing the tests resulting in rain as against no rain.

Beschreibung: An index chart and seven sector charts are given for use in providing an easy conversion from radiosonde (RAOB) or similar tropospheric sounding data of the total atmospheric pressure (millibars) the temperature (°C) and the water vapor mixing ratio (grams per kilogram) to the dielectric constant or the radio frequency index of refraction of the atmosphere. Reference is made to 17 reports and papers which indicate possible applications of these data and variations thereof.

Beschreibung: A 400-ft tower with an anemometer and an aspirated thermohm at each 50-ft interval and a precision wind vane at each 100-ft interval with indicators and recorders in the office building is described. With a “surface” observation level the lapse rate, hence degree of stability, is continuously recorded at nine levels; the character of mixing and amount of dilution of waste stack gases are thereby known.

Beschreibung: Dust whirls observed at the U. S. Naval Ordnance Test Station are described, and explanations are given for their behavior. It is shown that, although the conditions necessary for dust whirl formation are well-known, standard theories do not explain satisfactorily the dynamics of the vortex motion. Field observations, laboratory experiments, and theory all indicate that shearing motion is an important factor in dust whirl formation. It is suggested that the mechanism of small-scale convection currents is not so simple as usually assumed, but is related in many respects to the processes involved during the development of dust whirls.

Beschreibung: The relation between the slope of tropical low pressure axes and the tendency for such lows to deepen or fill has been studied during investigations carried on separately in the Atlantic and in the Pacific ocean areas. The preliminary conclusions drawn from each of the two studies differ considerably and are reviewed herein. Limitations upon the use of vertical wind shear computations in determining the slope of such pressure axes are discussed. Questions are raised regarding the assumption in such computations that the vertical shear of the observed wind is a good approximation of the shear of the geostrophic components. Illustrations are given of the fallacies of reasoning that may result from such an assumption in connection with tropical cyclones.

Beschreibung: As there are a very limited number of surface weather stations in ocean areas, a systematic method is presented for the study and utilization of all pilot reports. The method involves the use of a graph of time vs. the distance of a plane from the terminal. If a low pressure trough crosses the route, its position and motion along the route can be accurately established by the delta value reports from several planes. Reports which are inconsistent with those of other planes can readily be detected and discarded. The graph serves also as a simple prognostic chart in that the extrapolation of the lines which represent pressure systems or zones of bad weather will locate future positions of these weather areas.

Beschreibung: The theoretical researches on the problem of the disturbance of an atmospheric current flowing over a mountain range, carried on during the last ten years, prove that most of the characteristic observed features can be explained, to a very large extent, by the hydrodynamical theory of internal, small adiabatic perturbations in a stratified rotating atmosphere. In the case of a uniform current of velocity u, in which the coefficient of vertical stability is also uniform (θ is the potential temperature, g the gravity, z the elevation), the perturbation pattern corresponding to a smooth, low, gently-sloping mountain range varies widely according to the half-width a of this mountain range:i) If a is comparable to the critical value (Ls/2π) = (u/s) ≈ 1 km, there is a system of short stationary lee waves, or gravity waves, with the wave length Ls.ii) If a is comparable to (Lf/2π) = (u/f) ≈ 100 km, where f is the Coriolis parameter, there is a complex system of gravity-inertia lee waves, with the horizontal wave length Lf at ground level, and the vertical wave length Ls in the vertical plane of the crest.iii) In the case of a westerly wind, if a is comparable to the third critical value , where β is the latitudinal variation of f, there is a system of long geostrophic lee waves, of the type studied by Rossby, with the horizontal wave length Lβ at ground level.iv) In the other cases, there are no lee waves, and the wave system is either missing (cases a ≪ (u/s) and ≫ (u/f)) or restricted to the vicinity of the vertical plane of the crest, with the wave length Ls (case (u/s) ≪ a ≪ (u/f). One of the effects of the tropopause, and of atmospheric discontinuities in general, is to produce eventually an additional system of waves on the upwind side of the mountain range, but these waves must be generally much smaller than the lee waves. Similar results are obtained for a plateau with smooth sides, and in the case of a more complex mountain profile the perturbation can be computed by superimposing elementary solutions. If the current is not uniform, if the ground deformation is steep, or if the perturbation is not adiabatic, the preceding results are not valid, and the solution of the theoretical problem has been obtained in only very special cases.