Urban climate:

Question 1

The impact of urban forms and processes on local climate and weather:

Answer 1

Local climate is warmer in urban areas than rural areas this is down to the UHI effect.

Highest temperatures are found around the CBD.

Weather in urban areas, intense rainfall patterns are more frequent in urban areas due to high temperatures aswell as more condensation nuclei.
Not much snow in urban areas.

Question 2

Urban heat island effect:

Answer 2

4 main causes:

1) Absorption of heat by urban surfaces, e.g concrete and brick absorb and store heat from the sun throughout the day and then this is released overnight.

2) Air pollution, creates a pollution dome, which traps outgoing heat radiation

3) Heat from human activity

4) Less evapotranspiration, evapotranspiration uses heat energy so reduced evapotranspiration means higher temps

Question 3

Precipitation:

Answer 3

Frequency:
- Rain is more frequent in urban areas than rural areas.
- Higher condensation nuclei also increases frequency of fog.

Intensity:
- Rainfall is more intense in urban areas and there are likely to be more thunderstorms. Due to UHI and condensation nuclei.

Question 4

Fogs and thunderstorms in urban environments:

Answer 4

Fog is effectively cloud at ground level, higher concentration of condensation nuclei encourage the formation of it in urban areas. Fog and Mist tend to be thicker and last longer in high pressure conditions.

Thunderstorms, rising heat and air can cause late afternoon thunderstorms.

Air cools and condenses rapidly forming water droplets which can result in hail, which charge the thundercloud and discharge as lightning.

Question 5

Wind:

Answer 5

Urban structures slow, redirect and disturb the overall airflow.

Average wind speeds are usually lower in urban areas compared to rural areas as the buildings create friction which slows down the moving air.

Get powerful gusts when wind is channelled down streets, this is known as the Canyon effct.

Turbulence around buildings occurs as when wind hits the face of a building some of it is deflected down to the side and over the top.

Question 6

Air quality:

Answer 6

Urban activities create particulates that stay suspended in the air.

Sources of particulates include:
- Vehicle exhausts (80% of fine particulates in urban areas are from vehicle exhausts)
- Construction and mining, produce coarse particulates.

Particulates can cause health problems e.g asthma, lung cancer or heart disease.

Photochemical smog forms when particulates react with the UV light from the sun. This creates harmful secondary pollutants such as ozone.

When ozone is lower in the atmosphere this can cause health problems such as respiratory disorders.

Photochemical smog is a problem in many cities such as LA.

Question 7

Pollution reduction policies:

Answer 7

1) Congestion charging, charging people for using their vehicles in certain places at certain times e.g In Central London congestion charging reduced emissions by about 15%.

2) Public transport improvements. Improved bus schemes or bio gas buses, park and ride schemes. e.g Curitiba

3) Legislation. UK clean air acts of 1956 and 1968, introduced smoke control areas aswell as tall chimneys.

4) Alternative fuels, e.g electric cars (batteries) or biofuels (plants)