CUE 4 Urban Climate

Question 1

Describe the two layers that make up the urban dome

Answer 1

Urban canopy below roof level

Urban boundary layer area effected by heat island above roofs

Question 2

Give some examples of climactic variation within a city

Answer 2

Sunshine hours - 5-15% less
Average temperature 1 degree higher
5-10% more rainfall
100% more fog

Question 3

Describe albedo

Answer 3

A surfaces reflectivity
Low albedo less reflective therefore absorbs more
High albedo reflects more therefore absorbs less
Measured between 0-1 where 0 is total absorbtion

Question 4

Give three causes of the urban heat island

Answer 4

Urban surfaces - surfaces have extreme albedos, either absorb loads and slowly release overnight or very high which reflects a lot of energy
Air pollution- traps heat
Urban drainage - water removed much quicker, less light energy absorbed in evaporating
Biological heat - more people = more heat

Question 5

Give four issues caused by the urban heat island

Answer 5

Heat stroke + asthma
Positive feedback where conditions favour reactions with smog
Strains resources - hotter temps mean more air conditioning
Buildings deteriorate through chemical weathering

Question 6

Describe some stratagies to combat the urban heat island

Answer 6

Cool surfaces : higher albedo roofs
Green roofs, can reduce temp on rooftop by 20degrees
Urban greening : more shade
Cool cars : lighter coloured cars radiate less heat
Build buildings further from one and other - prevents heat from accumulating

Question 7

Why is there more rainfall in urban areas?

Answer 7

Convection rainfall
Buildings encourage uplift of air
Pollution creates hydroscopic nuclei

Question 8

Why is cloud cover high in urban areas?

Answer 8

More condensation nuclei

Convection currents - same as rainfall

Question 9

Give a specific example of an urban surface responsible for generating the urban heat island

Answer 9

Walkie talkie building

Focuses sunlight 70 degrees

Question 10

Describe why winds are stronger in urban areas

Answer 10

Buildings

1) exert frictional force creating turbulence
2) Venturi effect increased wind speed due to pressure gradients and smaller spaces
3) low pressure conditions

Question 11

Give some examples of the conditions caused by pollutants, name and explain the pollutant that causes these

Answer 11

Bronchitus
Emphysema
Astham
Particulates are small particles smaller than 10 micrometers causing respiratory problems

Question 12

Describe a temperature inversion

Answer 12

Warm air layer moves over a colder one
Disrupts thermal currents
Makes air more still hence pollutants build up

Question 13

Give some facts about the great smog of 1952

Answer 13

Deaths of 4000 people
Pea soupers
Buses and taxis stopped as couldnt see

Question 14

Describe some policies used to control pollution

Answer 14

Clean air acts - 1956 clean air act ensured smoke free areas, by increasing chimney hight,
Industry zoning - city planners build industry downwind of cities
Ultra low emission zones - exahust standards must be met in london
Congestion charge - £11.50 per day