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Winston T. L. Chow, Dean Brennan, and Anthony J. Brazel

The prodigious volume of applied and interdisciplinary heat island research in Phoenix, Arizona, was motivated by several factors intrinsic to the city and has contributed to formation of municipal policies geared toward sustainable urban climates. The desert city of Phoenix, Arizona, is the focal point of the expansive Phoenix Metropolitan Area (PMA) (~37,000 km 2 ) ( Fig. 1 ). Since 1950, the PMA has experienced extensive land use and land cover (LULC) alterations, changing from a

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R. W. Fonda, R. F. Dahms, J. E. Fralick, and K. M. Kendall

Three mid-winter thermal maps of Bellingham, Wash., are presented, two for clear-sky conditions and one for overcast conditions. Bellingham, a city of about 40,000 population, adjoins a large body of water and comprises a heterogeneous topographic and vegetation mosaic. The higher density section of the city is clearly warmer than the surrounding countryside, with a closed isotherm heat island associated with an area of tall buildings on a west-facing slope. In the eastern part of the city the combination of warmer zones on the sides of slopes and frost pockets at low points in a valley fits the model of Geiger for night-time valley temperature distribution. In addition, cold air drainage in one valley is blocked by a freeway embankment to intensify the frost pocket. The heterogeneous topography prevents large heat islands in Bellingham, but man-made structures markedly influence temperature distribution. Given proper planning of future domestic and industrial growth, Bellingham probably can avoid the creation of unfavorable thermal conditions.

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Richard J. Kopec

Studies of the heat island effect produced by urban centers have focused almost exclusively on large cities. Knowledge concerning the extent to which small places, i.e., towns with less than 50,000 people, exert a similar effect on their atmospheric environment is limited in this country. Only at Palo Alto, Calif., and Corvallis, Oreg., have such studies been conducted. This paper reports the results of temperature measurements and their spatial patterns taken by mobile traverses during the course of three seasons at Chapel Hill, N. C., and compares the heat island effect identified in this small university town with previous studies. The comparison shows a similarity among derived data which lends support to the ranking of urban places by population size as a climatic parameter.

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James R. Norwine

Woodfield Mall is a new shopping complex located in suburban Schaumburg, 25 miles west of Chicago. Located on a nearly “neutral” site (almost level topographically, with little surrounding residential or commercial development), Woodfield is the nation's largest enclosed multilevel shopping mall. During the period 1 January–31 March, 1972, temperatures were monitored at 84 predetermined sites on and near the grounds of the complex by means of automobile traverses. Sampling was between 2200 and 2300 hours GST. It was found that: a) a distinct but modest heat island ( = IF) existed at the building complex for the period as a whole; b) the heat island effect ranged from values as high as 4F on “favorable nights”—cold, clear, and calm—to negligible values on “unfavorable nights”—warm, cloudy, and windy; c) no appreciable mean temperature differences existed between the sampling sites south and west of the central building and those north east of it, at least in terms of average monthly values. It was concluded that a totally enclosed shopping center does create a definite heat island under proper meteorological conditions, but that the effect is probably less than that of comparable “traditional” shopping centers, which consist of numerous scattered buildings of various shapes and sizes.

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Cynthia Rosenzweig, William D. Solecki, Lily Parshall, Barry Lynn, Jennifer Cox, Richard Goldberg, Sara Hodges, Stuart Gaffin, Ronald B. Slosberg, Peter Savio, Frank Dunstan, and Mark Watson

This study of New York City, New York's, heat island and its potential mitigation was structured around research questions developed by project stakeholders working with a multidisciplinary team of researchers. Meteorological, remotely-sensed, and spatial data on the urban environment were brought together to understand multiple dimensions of New York City's heat island and the feasibility of mitigation strategies, including urban forestry, green roofs, and high-albedo surfaces. Heat island mitigation was simulated with the fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5). Results compare the possible effectiveness of mitigation strategies at reducing urban air temperature in six New York City neighborhoods and for New York City as a whole. Throughout the city, the most effective temperature-reduction strategy is to maximize the amount of vegetation, with a combination of tree planting and green roofs. This lowered simulated citywide surface urban air temperature by 0.4°C on average, and 0.7°C at 1500 Eastern Standard Time (EST), when the greatest temperature reductions tend to occur. Decreases of up to 1.1°C at 1500 EST occurred in some neighborhoods in Manhattan and Brooklyn, where there is more available area for implementing vegetation planting. New York City agencies are using project results to guide ongoing urban greening initiatives, particularly tree-planting programs.

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William H. Raymond, Robert M. Rabin, and Gary S. Wade

The Mississippi River floodplain in the states of Arkansas, Tennessee, Mississippi, and Louisiana presents a readily discernible feature in weather satellite images. This floodplain appears in the spring and early summer as a daytime warm anomaly at infrared (IR) wavelengths and as a bright reflective area at visible wavelengths. Remnants of this feature can occasionally be identified at nighttime in the IR satellite images. During June the normalized difference vegetation index identifies major contrasts between this intense agricultural region and the surrounding mixed-forest region. This distinction and the homogeneity of the floodplain, with its alluvial soil, contrast with the encircling region, creating an agricultural region containing heat island features. Thirty years of climatological surface station data for the month of June reveal that the surface air temperatures in the floodplain experience less diurnal variation than those in the surrounding regions. This is primarily because nighttime minimums are warmer in the Mississippi River floodplain.

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Andrew C. Comrie

Tucson, Arizona, is an example of the many cities in the southwestern United States experiencing rapid growth and urban sprawl over the last several decades. The accompanying extensive modification of land use and land cover leads to many environmental impacts, including urban heat islands. The primary aim of this paper is to expand knowledge of the phenomenon for Tucson, by quantifying the amount of urban warming, and by mapping temperature patterns over the city and examining related aspects of the local-scale atmospheric circulation. The secondary aim is to document how an applied empirical research project was integrated into an introductory undergraduate climatology class via active learning. The paper begins and concludes with general and practical comments on combining the research and educational aspects of the project.

An analysis of 30-yr temporal trends in urban and nonurban minimum temperatures across the region shows the rate of urban warming to be about three-quarters of the general regional warming. Tucson's urban heat island is ~3°C over the last century, with >2°C of this warming in the last 30 years. The annual average urban warming trend over the last three decades is 0.071°C yr−1 with the strongest effect in March and the weakest effect in November. There is evidence that the latter is caused by strong, near-surface winds under stable conditions. A case study is presented comprising field measurements and map analysis of urban temperatures and supporting variables for 13 February 1999. Measurements include comprehensive mapping using vehicle-mounted thermistors and numerous local meteorological observations from around the city. Wind speeds during the field measurements were somewhat stronger than is typical of heat island studies, up to 12 m s−1. Nonetheless, because of terrain-induced flows and land surface heterogeneity, complex temperature patterns were observed. Several transient katabatic flows off surrounding mountain ranges were detected, leading to localized cold pockets. Locally warm areas in other parts of the city are associated with terrain sheltering or local land surface heating. The central city showed a possible urban heating pattern with temperatures ~2°C higher than upwind rural air.

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I. D. Stewart and T. R. Oke

View of LCZ 1 in Seattle, Washington. Photo: I. D. Stewart The new “local climate zone” (LCZ) classification system provides a research framework for urban heat island studies and standardizes the worldwide exchange of urban temperature observations. The study of urban heat islands (UHIs) implicates two of the most serious environmental issues of the twentieth century: population growth and climate change. This partly explains why the worldwide stock of heat island studies has grown so

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Norbert Schörghofer, Steven Businger, and Matthias Leopold

than seasonal, character of these cold-air flows makes heat removal particularly efficient. Fig . 9. Schematic illustrations of inferred ventilation and cold-air accumulation in high-altitude ice-preserving microclimates on the island of Hawaii. (a) Craters (vertically exaggerated) can accumulate radiatively cooled air at night. This exceptionally cold air resides in the porous subsurface even at moderate wind speed. (b) The lava tube entrance pits, smaller than the craters, are ventilated, but

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C. N. Long, S. A. McFarlane, A. Del Genio, P. Minnis, T. P. Ackerman, J. Mather, J. Comstock, G. G. Mace, M. Jensen, and C. Jakob

A pair of permanent observing sites on the islands of Manus and Nauru have enhanced research into clouds, atmosphere, and radiation in a region where convective systems affect the entire globe It has long been recognized that the tropical western Pacific (TWP) warm pool area acts as the driver of a heat engine that exerts a significant influence on the global climate system. The area is typified by the warmest sea surface temperatures, highest atmospheric water vapor contents, and the greatest

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