URBAN ENVIRONMENTAL AND SOCIAL STRESSES

What causes temperatures to increase in urban areas and why? (5)

1. dark surfaces absorb more solar radiation

2. car engines and factory exhaust produce heat

3. fewer plants in urban settings mean less evaporate-transpitation occurs (a process that cools the air)

4. fewer trees (trees shade the ground, preventing heat from being absorbed)

what characteristics of urban climates (3)

1. lower relative humidity

2. higher pollution levels

3. usually lower wind speeds

what is the urban heat island effect

refers to the phenomenon where urban areas experience significantly warmer temperatures than surrounding rural areas (2-5ºC warmer)

describe where there are temperature sinks (falls), plateaus (remains the same) and cliffs (increases)

• the temperature sinks are found above green spaces and water

• plateaus occur in areas with the same land use

• cliffs occur when temperatures change rapidly form one land use to another

what are the 4 main causes of the urban heat island effect and why?

1. air pollution: pollution from cars, industry, etc. increases cloud cover and produces a pollution dome. both of these trap outgoing heat and reflect it to the surface

2. heat from human activity: air conditioning units, heating homes and offices, etc. all released heat to the surrounding area

3. absorption of heat by urban surfaces: urban surfaces have a low albedo

4. less evapotranspiration: removal of green spaces and trees reduces the cooling effect of evapotranspiration

describe the strategies to reduce the heat island effect (5)

• reduction of air pollution: reducing emissions by introducing clean air zones and congestion charges

• changes to building, design such as using reflective materials can reduce the absorption of heat

• adding gardens to rooftops can increase the amount of vegetation as well as decreasing heat absorption

• increasing the numbers of parks, gardens and vegetation to increase evapotranspiration which has a cooling effect

• the increase vegetation cover also improves air quality

what are the effects of poor urban air quality

• respiratory problems such as asthma

• increased haze through increased emissions of sulphur dioxides and nitrous oxides

• an increase in carbon dioxide, adding to the enhanced greenhouse effect and global warming

• photochemical oxidants cause eye irritations and headaches

• smog (happens when sunlight reacts with the chemical pollutants in the atmosphere and the uv light causes them to break down into secondary, harmful chemicals to form photochemical fog

what are 3 strategies of managing air pollution

• technical innovations, vehicle restrictions, government legislations

what are some examples of vehicle restrictions and how do they help manage air pollution.

• congestion charges: charging for using vehicles in certain places at certain times. this reduces pollution through a reduction in road traffic. however it can increase outer zone traffic and emissions as people try to avoid the charges by using alternative routes

• pedestrianisation: vehicles are restricted form entering certain places at certain times, this reduces emission through a reduction in road traffic

• improvements in public transport

what are the patter of traffic congestion

• increase during peak hours

• increase when there are events such as concerts or sporting competitions

• changes during seasonal variations

what are the impact of traffic congestion

1. increased pollution (more traffic leads to higher emissions)

2. longer and more unpredictable journey times (negatively impact the economy)