Date of Award

1979

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Earth & Environmental Systems

Abstract

The effect urban areas have on climate has long been recognized. Whereas substantial research has been published on observed modifications of climate in cities, little has been reported about the underlying causes of urban climates. A number of factors have been postulated as causes of urban climate, but recent studies indicate that urban land cover and waste heat from human activities are the primary factors that create urban climatic anomalies. Due to the complexity of urban landscapes little research has investigated the link between urban land cover and climatic modification. This study examined the relations between the physical nature of the urban interface and urban climate. The energy budget approach was used to extract the physical properties of the interface and contrast urban and rural interface physical conditions. Quantitative values for each interface physical property were compiled for representative urban and rural interface materials. A numerical simulation model of the relation between the net radiation budget and surface thermal response was developed and used to study the impact of varying each interface physical property. To confirm the results from energy budget analysis, remote sensor data collected by the ERIM (Environmental Research Institute of Michigan) M7 scanner of the Indianapolis, Indiana, urban interface were analyzed. Digital computer analysis procedures developed at LARS (Laboratory for Applications of Remote Sensing) of Purdue University and ISURSL (Indiana State University Remote Sensing Laboratory) were used to extract high-resolution spatial measurements of albedo and surface temperatures from the data. The measurements were examined statistically to verify the results derived through the energy budget analysis. Analysis of the remote sensor data confirmed the findings from the energy budget approach. The physical nature of the urban interface that evolved from this study differs considerably from the description that is commonly given in current urban climatic research. The urban interface is neither as complex nor as simplistic as previously expressed. Basic differences between urban and rural interface energy budgets were identified that result from replacement of vegetated soils with pavements and buildings. Construction of pavements and buildings modifies albedos, thermal properties, and subsurface structure of the interface. Vegetated surfaces, which have the property of reflecting a large percentage of near-infrared solar radiation, are replaced by materials that have a wide diversity of albedos but lack unique near-infrared relfectance properties. Soil moisture is effectively removed from the interface, thus reducing the magnitude of the latent heat flux in urban areas and altering the thermal properties or the interface, from dynamic characteristics that change in response to local meteorological conditions, to static characteristics that are determined by the physical nature of the material. As a result of subsurface structure, buildings have an energy budget that differs significantly from the energy budgets of pavements and natural surfaces. In addition, the results show evidence that waste heat from fuel consumption in buildings provides a significant contribution to urban energy budgets in the winter. The study demonstrates that the urban interface may be described as consisting of three basic elements: buildings, pavements, and natural surfaces. Urban energy budgets differ significantly from rural energy budgets as a result of the physical characteristics of the building and pavement landscape elements. The complex pattern of energy budgets within a city is explained by the distribution of these basic landscape elements.

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