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AUGUST H. AUER JR.

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August H. Auer Jr.

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August H. Auer Jr.

Abstract

The total concentration of ice crystals found in natural cap clouds appears to result from the nucleating behavior of at least two types of ice nuclei, i.e., freezing and deposition. The respective contributions of these two modes of nucleation have been partitioned by the use of techniques in which the identification of ice crystals resulting from frozen droplets can be made. Furthermore, the identification of deposition ice crystals at water saturation, when compared with similar data obtained during water subsaturated but ice supersaturated conditions, has yielded an insight as to the dependence of deposition ice crystal concentration (deposition nuclei) upon both temperature and ice supersaturation.

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August H. Auer Jr.

Abstract

Extensive aircraft observations of thermodynamical parameters, updrafts, condensation nuclei and turbulence were obtained of an isolated, non-precipitating, stationary cumulus cloud growing over a refinery complex. These observations and subsequent analyses may find utility in evaluation of numerical cloud models.

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August H. Auer Jr.

Abstract

A technique is described whereby the radar reflectivity can he combined with cloud-top temperature, from either satellite imagery and/or sounding analysis, to provide a reliable discrimination between heavy rain and/or hail in convective clouds. Hail sizing is also possible.

During an all-season operational evaluation throughout New Zealand, the discrimination scheme yielded a probability of detection of 91% with a false-alarm ratio of only 12%.

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August H. Auer Jr.

Abstract

Aerial reconnaissance of the greater St. Louis area has led to the identification and classification of land use types. The land use classification provides as much compatibility as possible with other classification systems, yet offers the inclusion of percentage vegetative cover as an innovative characteristic of the land use description. The observed meteorological (thermodynamic, kinematic and radiative) anomalies in the vicinity of the metropolitan area are shown to be affiliated with “meteorologically significant” land cover characteristics.

It is suggested that the specific details of population, areal extent and type of metropolitan land cover must be considered in estimating the potential for inadvertent weather modification.

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Mark J. Komp and August H. Auer Jr.

Abstract

Under the auspices of Project METROMEX, studies of visibility deterioration downwind of St. Louis were conducted during August 1976. Estimates of horizontal visibility and aerosol measurements were acquired upwind, over and downwind of the St. Louis metropolitan area, by means of airborne transects and standard meteorological data.

Reductions amounting to 50% of regional upwind visibilities have been observed; during a weekend study when light, urban vehicular and industrial activity was observed, visibilities within the anomaly were reduced by only 20%. The anomalies were situated between distances corresponding to 2–4 h travel time downwind for an air parcel moving with the mean transport wind. Several case studies noted improvement in the visual range after 4–5 h downwind.

The regions of minimum visibility do not coincide with locations of Aitken nucleus concentrations at 2–4 h downwind. Aerosol surface volume distributions indicate a general growth in the accumulation mode (0.1–1.0 μm) with maximum values in a much narrower size range within the mode of 0.2–0.3 μm diameter. These increases in the accumulation mode correspond to the size range in which particles are optically significant. Collaborative evidence from current literature suggests gas-to-particle reactions and/or gravitational sedimentation and coagulation as cause of the aerosol growth.

The ramifications of visibility deterioration near large metropolitan areas are demonstrated by a conceptual model.

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August H. Auer Jr. and Wayne Sand

Abstract

During the summers of 1964 and 1965, the Colorado State University Hail Suppression Research Project made updraft measurements beneath the base of cumulus and cumulonimbus clouds in northeastern Colorado. Analysis of the data reveals that the average maximum updraft appears to be located in the right-front quadrant of the radar echo. For heavily precipitating cumulonimbus clouds, this average maximum updraft exceeded 6 m sec−1. There is also a proportional increase in the magnitude of the updrafts relative to the amount of precipitation falling from the cloud. Average updrafts of all measurements on moderately and heavily precipitating cumulonimbi were 2.5 m sec−1 and 3.8 m sec−1, respectively. Much stronger updrafts can be expected on the common boundaries of converging cumulonimbus clouds. Updrafts appear to exhibit laminar flow characteristics with turbulence found upon entering and leaving the strong updraft regions. Smooth steady updrafts may exist for an hour or more, indicating that the more intense thunderstorms possess a steady-state phase. During this steady-state phase, areas of scud cloud were normally found in the areas of strongest updrafts. From a limited study, no apparent correlations were found between maximum updrafts observed and certain environmental parameters.

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David M. Shea and August H. Auer Jr.

Abstract

An instrumented aircraft equipped to measure temperature, humidity, turbulence, Aitken nuclei, and wind speed and direction was used to examine the thermal and aerosol plumes downwind of St. Louis, Mo., for four case studies with moderate winds, under the auspices of Project METROMEX. Cross-wind patterns out to 140 km were flown upwind, over and downwind of the city. Meteorologically instrumented vans, one of which was equipped to launch radiosondes, were also employed.

Thermodynamic perturbations in the mixing layer were limited to regions no more than 40 km (1.3 h travel time) downwind of the intense surface anomalies in the metropolitan area. The magnitude of the thermodynamic perturbations and their vertical extent are inversely related to the mixing layer wind speed.

In all cases, St. Louis and the adjacent Alton-Wood River industrial complex produced distinct aerosol plumes out to 100 km or more, but never more than 4 h travel time. Forty-five percent reductions in visibility were consistently detected in regions 2.5–3.0 h downwind of St. Louis. These locations did not coincide with those of maximum concentrations of Aitken nuclei.

A conceptual model describing various urban influences in the mid-day mixing layer downwind of a metropolitan area has been synthesized.

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David P. Murray and August H. Auer Jr.

Abstract

Observations using a double-theodolite system for tracking pilot balloons were made to further examine the effects of temperature lapse rates on pibal ascent rates. It was found that under stable atmospheric conditions balloon ascent was noticeably retarded. This retardation resulted in erroneous derived wind speed data when using single theodolite reduction procedures assuming a constant ascent rate.

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