Urban Heat Island Effect

What impacts do these pollutants have on people's health?

Result in respiratory problems, asthma, cancers and heart conditions, and eye irritation

What is an example of photochemical smog being made?

SO2 + H2O + O2 -> H2SO4 under sunlight

What pollutants are found in urban areas?

Sulphur dioxide, carbon dioxide, and oxides of nitrogen, including hydrocarbons

What happens during the night for LA's pollutant dome?

Surface warming of the sea by day and slower cooling at night so there is localised LP so the pollutant dome moves to the West.

How can tarmac increase the temperature of an urban area?

Tarmac and concrete and black and therefore absorb heat, they slowly release this during the night, keeping the area warmer during night time.

Why is Los Angeles prone to pollution domes?

There are the sea and the Rocky Mountains which are natural barriers that no longer relieve the area of pollution.

How can the presence of water make an area colder?

Usually rural areas have more water as in cities water is diverted away due to drains and surface runoff on the impermeable tarmac. If closer to water, more evapotranspiration takes place and results in less sensible heat (heat which can be felt) and less rising, so area is colder. Whereas this is reversed for urban areas.

How can the nature of building materials increase temperature in terms of reflectivity?

When UV radiation hits glass, it reflects heat, but this is absorbed by other materials such as tarmac

What happens during the day for LA's pollutant dome?

- Prevailing winds push the pollutant dome to the East but Rocky mountains are in the way. - Descending ocean currents = subsidence of air

How can wind speed influence the temperature?

- Wind speed is slower in urban areas due to deflection of wind over the high rise buildings - Whereas rural areas have higher wind speeds as there are less interruption so laminair flow - In cities, wind speeds can sometimes be increase due to Venturi tunneling effect if houses are in an iron-grid pattern

How can buildings height and arrangement affect the temperature of an urban area?

- Wind speeds increase as building gets taller in cities, but is deflected over the high rise buildings so slower wind speeds in cities - In rural areas there is more turbulent flow as houses are spaced apart and therefore wind can get trapped between houses - The closer the buildings the warmer the area

How much higher are the urban areas temperatures in comparison to rural areas in winter?

1-2 degrees higher

What is the subsidence/temperature inversion layer?

A partition between the warm air above and cold air below the pollutant dome

Why is pollution worse during high pressure systems?

Because there are no winds to carry away the pollution and therefore results in stagnant pollution

What is photochemical smog?

Caused by secondary air pollutants react with each other and sunlight and fog

How does smog/pollution make an urban area warmer?

Cities have lots of pollution, therefore making a pollutant dome, which absorbs long wave radiation so it's warmer

Why are urban areas generally warmer than rural?

Due to the urban heat island effect

Is pollution worse during High or low pressure systems?

High pressure

How can anthroprogenic factors make an area warmer?

In cities there are higher populations, means more human activity, breathing, burning of fossil fuels, heating systems, air conditioners, electricity and lighting, which releases more heat.

What does grass and vegetation do?

It stores less heat so colder in rural areas