Daily Spatial and Secular Variations of Atmospheric Humidity in a Small City

Richard J. Kopec Dept. of Geography, University of North Carolina, Chapel Hill 27514

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Abstract

An investigation of the effects of Chapel Hill, N.C., and its suburbs on the temporal and spatial patterns of dew point temperature was conducted in the early fall months of 1971. Six 55-mi traverses over city and non-city surfaces within restrictive limits of sky cover and wind velocity permitted the collecting of sufficient data for the construction and subsequent analyses of dew point maps. Approximately 650 recordings per traverse were made utilizing an EG & G Model 880 Dew Point Hygrometer. The study showed that humidity patterns at the meso-level conformed to urban-suburban control and their temporal variations indicated a reversal of high and low values from the city at night to the suburbs and rural areas during the day. In a like manner, the complexity of the spatial patterns intensifies from night to day with the afternoon observations showing the greatest range of values and the steepest gradients. The importance of the spatial aspect in studying atmospheric elements is made obvious in this study, and the need for similar investigations of the humidity variations displayed by cities of all sizes, in all seasons, and in climatically diverse regions is underscored.

Abstract

An investigation of the effects of Chapel Hill, N.C., and its suburbs on the temporal and spatial patterns of dew point temperature was conducted in the early fall months of 1971. Six 55-mi traverses over city and non-city surfaces within restrictive limits of sky cover and wind velocity permitted the collecting of sufficient data for the construction and subsequent analyses of dew point maps. Approximately 650 recordings per traverse were made utilizing an EG & G Model 880 Dew Point Hygrometer. The study showed that humidity patterns at the meso-level conformed to urban-suburban control and their temporal variations indicated a reversal of high and low values from the city at night to the suburbs and rural areas during the day. In a like manner, the complexity of the spatial patterns intensifies from night to day with the afternoon observations showing the greatest range of values and the steepest gradients. The importance of the spatial aspect in studying atmospheric elements is made obvious in this study, and the need for similar investigations of the humidity variations displayed by cities of all sizes, in all seasons, and in climatically diverse regions is underscored.

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