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CLAYTON H. REITAN

Abstract

Mean monthly values of precipitable water have been computed for radiosonde stations in the United States for the period 1946–56. The individual monthly values and an elementary statistical analysis are presented for 52 stations with data during all or part of the period.

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Clayton H. Reitan

Mean monthly values of precipitable water for about 50 stations in the United States are used to describe the amount and variation of moisture over the area. The average precipitable water over the United States is found to be 1.75 cm and to range from 0.94 cm in February to 2.99 cm in July. Monthly and yearly averages for the period 1946 to 1956 indicate that there is considerable variation on a monthly and sectional basis but that the yearly and overall area amounts of precipitable water are rather stable.

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Clayton H. Reitan

Abstract

Trends in cyclone frequencies over North America were determined for the period 1949–76 for four mid-season months. The general trend has been for a decrease in the number of cyclonic events, but with fluctuations. There is a tendency for the trends in frequency to be associated with trends in the mean temperature of the Northern Hemisphere and latitudinal temperature gradients as reported in the literature.

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Clayton H. Reitan

Abstract

The mean frequency of cyclonic events for North America is determined for five months based on the 20-year period, 1951–1970. Monthly maps are used to present the data and display the distribution of cyclonic frequencies. The frequencies of cyclogenesis are also determined and used to construct mean cyclone tracks. A subjective comparison between these data and cyclone frequencies from earlier studies reveals differences which do not appear to form a consistent pattern. Although some differences can be attributed to differences in the methods of analysis, others suggest significant variation between these years and the early 1900's.

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Clayton H. Reitan

Abstract

Mean monthly values of precipitable water were related to mean monthly values of surface dew point for 15 stations distributed over the continental United States. The degree of relationship was excellent, and a regression equation relating the two parameters was computed. Since surface dew point is so well related to precipitable water, this implies that the rate of decrease of moisture content through a deep layer tends toward a constant, which was approximately evaluated.

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Clayton H. Reitan and Joseph M. Moran

Abstract

Probabilities of setting record daily low temperatures during the winter half-year were determined empirically for selected stations in the upper Midwest. The probability of a new record low depends upon the length of station observational record, decreasing as record length increases. Thus, the probability of five or more record low daily temperatures during the winter period is about 0.5 for stations with 35 years of observations, and 0.1 at stations with 100 years of data. Frequency of occurrence of new record low daily temperatures is, therefore, an appropriate measure of the severity of a winter only if those frequencies are related to the length of the observational record at a particular station.

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Clayton H. Reitan and Roscoe R. Braham Jr.

Abstract

The concentrations of salt particles over central Illinois are being monitored through the use of a sodium flame-counter and an impactor. The number of large particles as determined by the impactor has been found to average about two per cubic meter, and high concentrations of the magnitude found over oceans have never been detected. It is concluded that these large salt particles are not found over mid-continents in sufficient numbers to initiate precipitation through a process of condensation and coalescence unless the chain-reaction process is also operative. There is no evidence that these large particles are necessarily carried inland from an oceanic source region.

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