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HOMER W. BALL

Abstract

SYNOPSIS

The Army, recognizing the necessity of having men training in meteorological work, to supervise and carry on such work in the military service, has established a course in meteorology in the Signal Corps School at Camp Alfred Vail, N. J. As this is the only school in the United States giving a vocational course in meteorology, the results included in a considerable period of time may be watched with great interest. To date a large majority of the men who took this course in the school are doing excellent work on the Signal Corps stations.

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John T. Ball and Keith W. Veigas

Abstract

The incorporation of diagnostic data obtained from surface observations into a humidity analysis at the 850-, 700- and 500-mb levels is tested using European surface and upper-air data for 22 observation times in February 1962. Sparse data conditions are simulated by withholding a portion of both surface and upper-air data. The rms errors and contingency table per cent correct scores indicate that an improved analysis is obtained in data sparse areas by weighting the diagnostic data relative to the radiosonde data. The most appropriate weighting is a function of the reliability of the diagnosis and the data density. The effects of using different initial guess fields, varying the application of the successive approximation technique (SAT) to these fields, and applying smoothing were also considered.

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Robert C. Balling Jr. and Sandra W. Brazel

Abstract

Summertime temperature, dewpoint, relative humidity, apparent temperature and weather stress levels have not changed significantly over the past 37 years at the Tucson, Arizona Municipal Airport. However, several of these variables show substantial trends during the most recent 18-year subperiod when the Tucson growth rate has been highest. The results for Tucson are quite different from the statistically significant changes in local climate reported for the Phoenix Airport during the same period of record. The differences in the changing weather conditions between these two desert cities appear to be related to (a) the smaller population in Tucson, (b) the position of the Tucson airport measurement site near the outskirts of the city as opposed to the centrally located airport in Phoenix and (c) the type of landscapes being replaced by these rapidly growing urban areas. The city of Phoenix is expanding generally into irrigated agricultural lands, while in Tucson, the bulk of the urban expansion is into the surrounding dryland areas. The results of this study are particularly useful in assessing the impact of urbanization on the local climate within a desert region.

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Sandra W. Brazel and Robert C. Balling Jr.

Abstract

Long-term monthly averaged dew point and relative humidity levels for Phoenix, Arizona are examined in this investigation. Dew points are generally unchanged over the 1896–1984 period of instrumental record; relative humidities have dropped sharply during the recent decades. Changes in local land use and a developing urban heat island are suggested causes of the observed patterns in the Phoenix atmospheric moisture levels.

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Robert C. Balling Jr. and Sandra W. Brazel

Abstract

This paper identifies the spatial and temporal patterns in diurnal variations of Arizona's monsoon precipitation frequencies. Long-term (1948–83) hourly rainfall data reveal a strong nocturnal tendency in the Salt and Gila River basins of central Arizona. First harmonic phase angles suggest that storms tend to develop into the Phoenix area from all directions to ultimately produce a strong maximum frequency near midnight over the city. Other areas of the state appear to have the more normal daytime maximum in their monsoon precipitation. The practical and theoretical utility of the results are briefly discussed.

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Donald A. Chisholm, John T. Ball, Keith W. Veigas, and Paul V. Luty

Abstract

Northern Hemisphere surface-synoptic and radiosonde data from November 1961 through February 1962 are used to develop diagnostic relationships between surface-observed variables at a single station and the dewpoint spread at the 850-, 700-, 500- and 400-mb levels above that station. The approach consists of two steps: 1) the isolation within a decision-tree framework of those cases for which individual surface-observed variables yield highly reliable estimates of upper-level humidity, and 2) the application of a statistical technique (Regression Estimation of Event Probabilities) to the remaining cases to derive equations yielding probabilities of occurrence of specified categories of dewpoint spread. This approach yields useful diagnostic information with a quantitative measure of reliability.

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G. Chiodo, L. M. Polvani, D. R. Marsh, A. Stenke, W. Ball, E. Rozanov, S. Muthers, and K. Tsigaridis

Abstract

An accurate quantification of the stratospheric ozone feedback in climate change simulations requires knowledge of the ozone response to increased greenhouse gases. Here, an analysis is presented of the ozone layer response to an abrupt quadrupling of CO2 concentrations in four chemistry–climate models. The authors show that increased CO2 levels lead to a decrease in ozone concentrations in the tropical lower stratosphere, and an increase over the high latitudes and throughout the upper stratosphere. This pattern is robust across all models examined here, although important intermodel differences in the magnitude of the response are found. As a result of the cancellation between the upper- and lower-stratospheric ozone, the total column ozone response in the tropics is small, and appears to be model dependent. A substantial portion of the spread in the tropical column ozone is tied to intermodel spread in upwelling. The high-latitude ozone response is strongly seasonally dependent, and shows increases peaking in late winter and spring of each hemisphere, with prominent longitudinal asymmetries. The range of ozone responses to CO2 reported in this paper has the potential to induce significant radiative and dynamical effects on the simulated climate. Hence, these results highlight the need of using an ozone dataset consistent with CO2 forcing in models involved in climate sensitivity studies.

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Jonny W. Malloy, Daniel S. Krahenbuhl, Chad E. Bush, Robert C. Balling Jr., Michael M. Santoro, Joshua R. White, Renée C. Elder, Matthew B. Pace, and Randall S. Cerveny

Abstract

This study explores long-term deviations from wind averages, specifically near the surface across central North America and adjoining oceans (25°–50°N, 60°–130°W) for 1979–2012 (408 months) by utilizing the North American Regional Reanalysis 10-m wind climate datasets. Regions where periods of anomalous wind speeds were observed (i.e., 1 standard deviation below/above both the long-term mean annual and mean monthly wind speeds at each grid point) were identified. These two climatic extremes were classified as wind lulls (WLs; below) or wind blows (WBs; above). Major findings for the North American study domain indicate that 1) mean annual wind speeds range from 1–3 m s−1 (Intermountain West) to over 7 m s−1 (offshore the East and West Coasts), 2) mean durations for WLs and WBs are high for much of the southeastern United States and for the open waters of the North Atlantic Ocean, respectively, 3) the longest WL/WB episodes for the majority of locations have historically not exceeded 5 months, 4) WLs and WBs are most common during June and October, respectively, for the upper Midwest, 5) WLs are least frequent over the southwestern United States during the North American monsoon, and 6) no significant anomalous wind trends exist over land or sea.

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