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F. A. Huff

Abstract

A study was made of the association of potato leafhopper influxes into Illinois with existing synoptic weather conditions. With data for 25 observed influxes during 1951–59, synoptic weather maps and climatological records were studied to obtain information during and preceding the flights on: wind conditions between the Louisiana source region and Illinois; the presence of fronts in Illinois; the extent and intensity of rainfall in the state; and prevailing temperature conditions.

Results of the study indicated a strong relationship between synoptic weather conditions and leafhopper influxes. Typical meteorological conditions favoring influxes were found to be: a persistent southerly flow of maritime tropical air from the Gulf states into the Midwest for at least 36 hours prior to the Illinois influx; rainshowers or thundershowers on the days of influx; and, the presence of a front, usually a cold front, at the time of the recorded influx.

From the above criteria, days favorable for influxes during 1960 were predicted. Excellent correspondence was obtained between indicated and actual dates of 1960 influxes.

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F. A. Huff

Abstract

Correlation and regression analyses were employed to evaluate the relation between summer hail patterns in Illinois and the climatological distribution of other meteorological elements, after dividing the state into sections with similar climatological characteristics. The distributions of thunderstorms, rainfall, maximum air temperature, dew-point temperature, and synoptic weather fronts were related to the hail distribution. Relatively strong association was found between the hail distribution and the combination of these five climatological elements, when multiple correlation analysis was performed and regression equations developed. The results of the study indicate that in a region of minor topographic influences, such as Illinois, the hail distribution can be explained largely by relating it to the multiple effects of other climatic events, whose distributions are determined by atmospheric conditions which are related to hail development. The Illinois study suggests that the frontal distribution pattern strongly influences the location of centers of maximum hail frequency.

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F. A. Huff

Abstract

Data from two dense rain gage networks in Illinois and Oklahoma were used to evaluate the feasibility of improving radar estimates of storm mean rainfall through the use of surface rain gage data to modify the radar-rainfall equation for specific storm conditions. Data were used from 19 storms and the evaluation restricted to warm-season, unstable precipitation and to the use of 10-cm radar. Evaluations were made of 1) the optimum accuracy which could be expected from radar measurements of rainfall on an ungaged area when rain gage data on adjacent gaged areas are used for adjustment of the radar estimates, and 2) the accuracy obtainable from adjustments of radar estimates with rain gage data from within the area of interest, based upon various rain gage densities in the sampling area. It was concluded that the normal climatic network is inadequate for modification of the radar-rainfall equation in warm-season storms in the Midwest if a relatively accurate estimate of storm mean rainfall is needed. However, comparison of isoecho and isohyetal patterns showed that the correspondence of radar and rain gage patterns was much better with 10-cm radar than it had been in earlier studies with 3-cm radar. It is recommended that future efforts be concentrated on improving direct measurements of rainfall from radar echo presentations.

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F. A. Huff

Abstract

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F. A. Huff

Abstract

Data from two dense networks of raingages in Illinois were used to obtain estimates of sampling errors in the measurement of areal mean precipitation on areas of 50–550 mi2 with investigations being made of storm, monthly, and seasonal precipitation. Storm data were grouped also according to season, precipitation type, and synoptic storm type to evaluate the relation between these factors and the sampling error. Storm sampling error was then related to areal mean precipitation, storm duration, area, and gage density within each data grouping. Several transformations of the above parameters were tested and results indicated a slight superiority for logarithms, followed by cube roots, square roots, and a logarithm-square root combination of the parameters. For a given sampling error, the gage density needed in warm season storms was 2–3 times greater than that required in the colder part of the year. Air mass storms required the greatest sampling density among synoptic storm types. Unstable types of rainfall in the warm season were found to require twice as many gages as steady rain. Considerable difference in the magnitude of storm sampling errors was found between consecutive 5-year periods on the same network, as well as between storms with apparently similar characteristics. Sampling requirements for monthly and seasonal precipitation were substantially lower than for storms.

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F. A. Huff

Abstract

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F. A. Huff

Abstract

A study has been made of the climatological characteristics of storm precipitation on a point and areal basis through the use of two sets of data. One is from a 12-year operation of a dense raingage network on 400 mi2 in central Illinois, and the other is the long-term point rainfall records of daily precipitation from U. S. Weather Bureau climatic stations throughout the state. The detailed network data were used to investigate effects of storm intensity and duration, precipitation type, synoptic weather type, wet and dry periods, and other factors upon storm distribution characteristics. Frequency distributions of both rainfall depth and number of storms were determined for various classifications, and these distributions were evaluated with respect to implications in weather modification during the critical growing season (May-September) and the water-supply replenishment period (October-April). Nomograms were developed from the climatological distributions to facilitate the evaluations. By relating areal to point distributions, a method was devised for deriving similar information for less dense network areas.

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F. A. Huff

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F. A. Huff
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F. A. Huff

A summary of present knowledge on the effects of waste heat and water vapor discharged from large cooling towers on augmentation of the natural precipitation downwind of such installations is presented. Available information is used to provide some insight into the potential quantitative effects. It is concluded that atmospheric scientists have not acquired adequate information at this time to define in quantitative terms the meteorological consequences of the large amounts of heat energy and water vapor released into the atmosphere from cooling towers associated with large power plants, and that atmospheric research should be initiated at once to alleviate the lack of knowledge on this pertinent environmental problem. Some basic recommendations for the type and duration of needed research are presented.

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