Understanding Microclimates and Urban Development Impact on Weather

1. How Man Affects The Weather Micrometeorology and Microclimates

2. Regional Climate • Regional climate describes the general climatic conditions of the locality that plants and animals inhabit, but it does not describe the actual climate in which they live. • organisms encounter a wide range of local temperature, moisture, precipitation and wind conditions that are influenced by soil, vegetation, ground cover, slope gradient, aspect (direction the slope faces), and other factors that vary greatly from one location to another. • The climate at a very local scale that influences the presence and distribution of organisms is known as the microclimate.

3. Microclimates • A microclimate is the climate of a small area that is different from the area around it. It may be warmer or colder, wetter or drier, or more or less prone to frosts. • Microclimates may be quite small - a protected courtyard next to a building, for example, that is warmer than an exposed field nearby. Or a microclimate may be extensive - a band extending several miles inland from a large body of water that moderates temperatures.

4. Micrometeorology • Micrometeorology is the study of weather related phenomena on a very local scale. Very local scale means, for example, the difference in temperature between the sunny and shady side of the tree or rock. It also includes variations in relative humidity between a forest and a nearby open area.

5. Vegetation involved in Climate • Plants respond to their minor variations in climate mainly by growing in favorable sites and not in unfavorable ones. Another example might be moss growing on the shaded side of a tree, rock, or building but not on the sunny side.

6. The Importance of Vegetation • By altering wind movement, evaporation, moisture, and soil temperatures, vegetation influences the microclimate of an area, especially near the ground. • Temperatures at ground level in the shade are lower than those in places exposed to sun and wind. • Vegetation reduces the steepness of the temperature gradient above the ground surface and influences relative humidity and the height of the active surface, the surface of any object that receives or is impacted directly by solar radiation. • Vegetative cover will also influence the extremes and daily maximum and minimum temperatures.

7. Developed Environments • Urban, suburban, and rural communities are the three main types of developed environments. All three of these environments have both common and unique land cover types. Each land cover may affect local air temperatures differently because of unique thermal properties. • These areas have natural surfaces and impervious surfaces.

8. Impervious Surface • Impervious surface: A hard surface area that either prevents or retards the entry of water into the soil mantle as under natural conditions prior to development and/or a hard surface area that causes water to run off the surface in greater quantities or at an increased rate of flow from the flow present under natural conditions prior to development. • Common impervious surfaces include, rooftops, walkways, patios, driveways, parking lots, storage areas, concrete or asphalt paving, gravel roads, packed earthen materials, and oiled, macadam, or other surfaces that similarly impede the natural infiltration of urban runoff.

9. Where we live • According to the latest U.S. Census, there are over 300 million people that live in the United States today. Our population lives in a variety of places, which can be divided into three main categories: urban, suburban, and rural areas.

10. Impervious Surfaces &Urban Growth • As cities grow and more development occurs, the natural landscape is replaced by roads, buildings, housing developments, and parking lots. • The metro Atlanta region has experienced explosive growth over the last 50 years, and, along with it, large amounts of impervious surfaces have replaced the natural landscape. • Impervious surfaces can have an effect on local streams, both in water quality and stream flow and flooding characteristics. • Impervious surfaces can also affect the temperature of the region.

11. Urban • People often define urban areas, or cities, as land occupied by buildings and other structures used for residences and institutional and industrial sites. • Urban areas often have some form of public transportation, such as buses, subways, or trains and have high population densities. • Buildings are often closer together and built higher than those in suburban or rural areas. • Urban areas are highly populated.

12. Suburban • Suburban areas are those on the outskirts of cities. • Residents of suburban areas often commute to the cities for work. Some suburban areas have commuter trains and buses that shuttle people to and from the cities. • Structures in suburban communities are often lower and farther apart than in cities. • Though they have smaller populations than cities, suburbs offer the same services including schools, health care facilities, and public works.

13. Rural • The 2000 Census showed that 59 million people live in rural areas. These are areas with large amounts of land with significantly lower populations than urban or suburban areas. • Structures are often far apart and some rural communities share hospitals or schools. • Rural areas tend to be far from urban areas. Some examples of rural areas include farmland, woodland forests, plains, deserts, and prairies.

14. What Is an Urban Heat Island? • As urban areas develop, changes occur in their landscape. Buildings, roads, and other infrastructure replace open land and vegetation. Surfaces that were once permeable and moist become impermeable and dry.1 These changes cause urban regions to become warmer than their rural surroundings, forming an "island" of higher temperatures in the landscape.

15. Where heat islands occur • Heat islands occur on the surface and in the atmosphere. On a hot, sunny summer day, the sun can heat dry, exposed urban surfaces, such as roofs and pavement, to temperatures 50–90°F (27–50°C) hotter than the air,2 while shaded or moist surfaces—often in more rural surroundings—remain close to air temperatures. Surface urban heat islands are typically present day and night, but tend to be strongest during the day when the sun is shining.

16. Atmospheric Heat Islands • In contrast, atmospheric urban heat islands are often weak during the late morning and throughout the day and become more pronounced after sunset due to the slow release of heat from urban infrastructure. The annual mean air temperature of a city with 1 million people or more can be 1.8–5.4°F (1–3°C) warmer than its surroundings.3 On a clear, calm night, however, the temperature difference can be as much as 22°F (12°C).3

17. Why Do We Care About Heat Islands? • Heat islands can affect communities by increasing summertime peak energy demand, air conditioning costs, air pollution and greenhouse gas emissions, heat-related illness and mortality, and water quality.

18. High Energy Demand • Increased energy consumption: Higher temperatures in summer increase energy demand for cooling and add pressure to the electricity grid during peak periods of demand. One study estimates that the heat island effect is responsible for 5–10% of peak electricity demand for cooling buildings in cities.3

19. Increased Emissions • Elevated emissions of air pollutants and greenhouse gases: Increasing energy demand generally results in greater emissions of air pollutants and greenhouse gas emissions from power plants. Higher air temperatures also promote the formation of ground-level ozone.

20. Quality of Life • Compromised human health and comfort: Warmer days and nights, along with higher air pollution levels, can contribute to general discomfort, respiratory difficulties, heat cramps and exhaustion, non-fatal heat stroke, and heat-related mortality.

21. Water Quality • Impaired water quality: Hot pavement and rooftop surfaces transfer their excess heat to stormwater, which then drains into storm sewers and raises water temperatures as it is released into streams, rivers, ponds, and lakes. Rapid temperature changes can be stressful to aquatic ecosystems.

22. What Can Be Done? • Communities can take a number of steps to reduce the heat island effect, using four main strategies: • increasing tree and vegetative cover • creating green roofs (also called "rooftop gardens" or "eco-roofs") • using cool or green pavements • installing cool or reflective roofs

23. Green Rooftops • A green roof is a roof of a building that is partially or completely covered with vegetation and soil, or a growing medium, planted over a waterproofing membrane. • The term "green roof" may also be used to indicate roofs that utilize some form of "green" technology, such as solar panels or a photovoltaic module. • Green roofs are also referred to as eco-roofs, vegetated roofs, living roofs, and greenroofs.

24. Advantages • Economic Advantages • Air Quality • Water Quality • Heat Dissipation

25. Cool Pavement • The term refers to materials chosen to reduce pavement temperature by increasing pavement reflectivity or controlling temperature by other means through choice of materials and engineering design

26. Construction of Pervious Pavement • Pervious pavements can be made of concrete, asphalt, open-celled stones, and gravel, that are mixed in a manner that creates an open cell structure allowing water and air to pass through.

27. Advantages • Because pervious pavements allow rainwater to seep into the ground through the pavement: • Vegetation is watered, reducing the need for irrigation • Ground water is recharged • Water resources are preserved • Stormwater runoff is reduced • Stormwater runoff quality isimproved

28. Free Response • Describe how the temperature of urban areas like Atlanta, Philadelphia, and Chicago differs from that of surrounding rural areas. • Identify and describe TWO differences between urban and surrounding rural areas that contribute to the temperature differences between them. • Urban areas typically have levels of air pollution that are significantly higher than those found in surrounding rural areas. Identify a characteristic of the urban microclimate that lead to higher levels of air pollution and describe how that characteristic contributes to this increase • Identify and describe TWO actions that local governments in urban areas could take to reduce air pollution.

29. Question 1: Describe how the temperature of urban areas like Atlanta, Philadelphia, and Chicago differs from that of surrounding rural areas. • Temperatures in urban areas tend to be higher than those in rural areas. This temperature difference is called the “urban heat island effect” and is typically larger during the night-time hours.

30. Question 2: Identify and describe TWO differences between urban and surrounding rural areas that contribute to the temperature differences between them. • There is more asphalt, concrete and buildings in urban areas and fewer trees and vegetation. • Fewer trees and vegetation reduce the natural cooling cycle. • Buildings block radiation, increasing temperature. • More trees, factories and machines • heat is a by-product of combustion • Tall buildings and narrow streets in urban areas • trap warm air, reduce cooling by convection • More people inhabit urban areas • higher population requires more housing, air conditioning, demand for fossil fuels

31. Question 3: Urban areas typically have levels of air pollution that are significantly higher than those found in surrounding rural areas. Identify a characteristic of the urban microclimate that lead to higher levels of air pollution and describe how that characteristic contributes to this increase • Increased combustion from many machines • increased temperature, particulates, greenhouse gases • industrial processes • harmful emissions • Urban development • increased particulates from exposed soil • Tall buildings • trap pollutants, limit airflow • Less vegetation • less filtering or absorption of particulates, or CO, Sox, Nox and ozone • Urban Heat Island Effect • Ozone formation due to photochemical reactions

32. Question 4: Identify and describe TWO actions that local governments in urban areas could take to reduce air pollution. • incentives or taxes • laws or regulations • direct actions like building mass transit, plant vegetation, HOV • Education • reduce the number of motor vehicles • improve fuel efficiency • reduce fossil fuel use