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A. Nelson Dingle

Abstract

Because of its relative insensitivity to changes of station location and to such natural phenomena as volcanic activity, precipitation is a promising weather element for the study of secular changes of the general circulation. A study of the precipitation records for individual stations, smoothed by the use of decadal moving averages, suggests that the prominent precipitation trends are continuous in time and space. A preliminary synoptic study of the interdecadal changes of average precipitation reveals details of the circulation changes in regard to cyclonic activity and moisture supply.

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A. Nelson Dingle

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A. Nelson Dingle

The standard gravity slide method of obtaining hay fever pollen counts is examined in relation to the volumetric method. Scrutiny of calibration data in the light of weather information reveals three interesting weather-related sequences of pollen concentrations. The gravity slide counts appear to represent the pollen concentrations quite poorly.

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A. Nelson Dingle and Yean Lee

Abstract

The fate of airborne contaminants that enter a cloud with an overriding rain, independently generated, is considered by means of three differential equations which express the overall mass conservation of contaminant. The model incorporates the physical processes of diffusive attachment, impact collection avid accretion, and includes consideration of particle and cloud droplet size spectra. The rainout ratio and rainout efficiency are evaluated on the basis of the theoretical results, and the general expressions for different cloud conditions are proposed.

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A. Nelson Dingle and Donald F. Gatz

Abstract

The rain cleansing patterns observed in five rain situations, all characterized by convective structures, are presented. The data comprise radioactivity and pollen concentrations measured in sequential samples of rain water from each rain. The rain systems are categorized, three being classed as “well-organized,” and the remaining two as “diffuse” convective systems. The temporal patterns of rain water contamination are relatively consistent in the well-organized showers, but much less so in the diffuse ones. Because the scavenging patterns of the pollens are quite parallel with those of the long-lived radioactive debris, it is inferred that both classes of contaminant enter the rain-producing parts of the showers by the same route, namely, in the low-level air that forms the convective updraft. It is therefore proposed that contamination that enters the troposphere from above (the stratospheric nuclear test debris reservoir) is not importantly scavenged until it passes through a low level tropospheric trajectory. The cleansing accomplished by the diffuse showers shows a tendency to be quite spotty, leaving pockets of contaminated air relatively unaffected between showers.

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Per B. Storebø and A. Nelson Dingle

Abstract

A configuration with rain falling through a shallow flow of pollution-loaded air is examined theoretically. The pollution particles are made up of (NH4)2SO4 mixed with graphite. A numerical feedback technique is used for calculating the development of the droplets having the particles as nuclei, as they pass over a 300 m high ridge under steady exposure to removal by raindrops.

The development of state parameters for air and vapor, together with droplet sizes, temperatures, equilibrium humidities, and rate of removal over the distributions are discussed. Dissipation of kinetic fall energy for droplets is shown to affect droplet behavior. Removal of pollution from low-level air by rain appears to be quite efficient.

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Kashinath S. Bhatki and A. Nelson Dingle

Abstract

A radiochemical procedure developed to measure precisely nanogram amounts of the indium tracer used in the study of circulations and rain scavenging processes in severe convective storms is described. The tracer indium collected in rainwater is normally associated with sodium, manganese and arsenic as major impurities. The method, therefore, is devised to remove arsenic as sulphide by thioacetamide precipitation followed by the extraction of indium bromide with isopropyl ether. The ether extraction separates it from sodium, manganese and lanthanum which is used as a flux monitor. The final purification of indium, from iron and other extracted impurities like gallium, in a form suitable for counting, is done by cation exchange resin separation.

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A. Nelson Dingle and Hal F. Schulte Jr.

Abstract

The photoelectric raindrop-size spectrometer, developed to meet the need in modern meteorology for detailed information about rain, is described. Operating with minimum physical disturbance of the rain field, the present instrument scans a 9.33-liter volume each second registering the size (surface area) and time of observation of each raindrop. The output of the instrument can be recorded in various stages of analysis by the use of electronic readout devices.

Data obtained to date reveal interesting new information about the behavior of raindrop spectra and about the spatial distribution of drops in heavy shower rain.

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A. Nelson Dingle, Donald F. Gatz, and John W. Winchester

Abstract

In an effort to determine whether it is feasible to use tracer techniques in the study of circulations and rain scavenging processes in severe convective storms, a pilot experiment using indium as tracer was conducted. A total of 200 gm of indium was released over a period of 21 min into the updraft feeding a relatively small convective system. The tracer was released by means of pyrotechnic flares from an airplane flying at about 3200 ft altitude. The rainfall from the system was sampled at the ground by means of an array of samplers placed and recovered by two mobile units. Analysis of the samples compared against analyses of untagged rain samples and reagent backgrounds of indium distinctly indicates the presence of tracer indium in a reasonable distribution pattern.

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Donald F. Gatz, A. Nelson Dingle, and John W. Winchester

Abstract

In a test of the use of indium as a particulate atmospheric tracer, both tagged and untagged rain showers were sampled at ground level in Oklahoma during May 1967. In 29 samples of untagged rain 6±3 nanograms of In per liter were found, indicating a natural background somewhat above the reagent blank of about 2 ng liter−1. After aircraft injection at cloud base of 200 gm of indium, as finely divided particles from pyrotechnic flares, a maximum of 40 ng liter−1 was found in the rain, and a pattern of localization of the tracer indium was revealed in an array of 14 samplers spaced over 11 km. The procedure for analysis began in the field with 1) addition of HC1 to the polyethylene samplers before rain was collected to ensure solubility of the tracer, 2) filtration to remove suspended solids, 3) addition of lanthanum internal standard, Fe+++, and NH3 to each 1-liter sample to precipitate In and La with Fe(OH)3, and 4) membrane filtration of the Fe(OH)3. At The University of Michigan the procedure continued with 5) reactor neutron activation of the filters, 6) separation of In from La by isopropyl ether extraction from HBr solution, and 7) assay of In and La radioactivities by β and γ, counting, respectively. The sensitivity of the method is determined by the natural background of the indium found.

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