Abstract: It has been well known that an urban heat island (UHI) occurs when urban areas experience higher temperatures than their surrounding rural areas, in particular at night. The temperature difference between urban areas and surrounding less-developed rural areas (a parameter called UHI intensity) mainly occurs due to the differences in surface characteristics (i.e. asphalt, steel, and brick in urban areas versus plants, grass, trees and farmland in rural areas), resulting in urban surfaces absorbing and storing heat more than rural areas.
However, our inability to predict the future course of UHI intensity for different types and sizes of urban areas around the world remains one of the primary sources of uncertainty in our understanding of meteorological processes in the atmosphere over urban areas. Meanwhile, the number of people living in urban areas around the world is projected to reach 68% by 2050, thus better forecasts over these areas are vital. Past research emphasized the UHI characterization for major metropolitan areas in the US and other parts of the world with limited or no attention to the extreme heat situation and UHI in relatively smaller sized cities (e.g. cities with a population of few hundred thousands). Several atmospheric processes are directly or indirectly governed by UHI. For instance, the UHI governs the dispersion of pollutants and gases regulating air quality and affects the formation of clouds and patterns of rainfall around the cities. Additionally, UHI impacts on health and well-being of populations is further exacerbated during heat waves because high temperatures cause significant health concerns in the summer, affecting morbidity and mortality. We argue that “small cities matter” for all types of UHI-induced meteorological processes. Additionally, a key problem exists in the UHI definition itself. It is unclear how the mean wind over a broad region affects the spatial temperature distribution, a process called urban heat advection (UHA). It is also unclear how weather forecasting models assess advection under different weather conditions in different seasons. Thus, we believe that without the consideration of UHA, quantification and forecasting of UHI will remain challenging.
This project aims to obtain a better picture of the spatial variability in urban heat and its advection and to understand UHI pattern and magnitude in different heat regimes using a new network of near-surface observations of meteorological variables within and around a small city located in an arid region (Lubbock, TX) for a year-long period. We will also compare results from weather forecasting models against the collected observations under widely varying weather conditions and will collect observations using weather balloons and laser instruments deployed during field campaigns. We will also use available satellite measurements of surface temperature as an independent source of observations.
We will be able to establish the quantitative aspects of the UHI for different wind patterns which have not been considered yet in UHI forecasts. More fundamentally, this project will create pathways for interpretation of the UHI over any city. In collaboration with the local Weather Forecast Office in Lubbock, this work will facilitate better forecasts for heat extremes and provide important information for planning outdoor events (e.g., school playgrounds, neighborhood parks, outdoor sports, recreation) and can help the public avoid excessive heat-related hazards. Finally, this work will provide new observations that will help improve operational forecasts of urban heat while establishing the fact that “small cities” also require better urban planning and risk management than is currently present.