Climate on a local scale - UHI

Question 1

Define microclimate

Answer 1

Where weather is different from the surrounding rural area in terms of temp, humidity, precipitation, visibility and air quality

Question 2

How do buildings affect the micrclimate

Answer 2

buildings have low albedo and absorb more heat

tall buildings and mixed height affects the way air flows across the city

Question 3

How does PM affect the micro climate

Answer 3

acts as a condensation nuclei which affects the amount of sunlight and the nuclei affects moisture

Question 4

What is an UHI

Answer 4

a warm spot in a surrounding cooler rural area

Question 5

What can temp difference vary between in a UHI

Answer 5

0.6 degrees in the day and 3-4 degrees at night

Question 6

What can the difference in temp in an UHI reach up to i summer

Answer 6

5 degree

Question 7

What is the average difference of London’s UHI

Answer 7

1.3 degrees

Question 8

How do buildings affect the UHI

Answer 8

artifical materials have a low albedo therefore higher thermal heat capacity which allows buildings to store heat during the day and release it at night by radiation

Question 9

How do windows on buildings affect the UHI

Answer 9

large windows have a large reflective capacity and concentrate heat

Question 10

Where does further heat come from in UHI

Answer 10

industry, vehicles and buildings

Question 11

How does pollution affect the UHI

Answer 11

creates a pollution dome allowing short wave radiation to enter but trapping radiation from escaping producing a greenhouse effect

Question 12

How does the amount of water in urban areas affect the UHI

Answer 12

water is artificially removed therefore less energy is used for evpo-transipartion and more energy can be used for heating

Question 13

When is the UHI most noticeable

Answer 13

in anti-cyclonic, HP conditions where winds are low resulting in less dispersion
In winter when a bigger impact from heating from within the city
at night when effect of isolation is absent and surfaces radiate heat

Question 14

How does the UHI change over space?

Answer 14

abrupt temp change at the rual-urban boundary
temp peak in centre in CBD where building density is the greatest
gentle increase of 2-4 degree per 1km which is know as a plateau but will be variations within due to open spaces etc

Question 15

How is precipitation effected by the UHI

Answer 15

increase an an increase in temp encourages the formation of LP zones with convectional rainfall and thunderstorms being more common

Question 16

Why is precipitation increased in the UHI

Answer 16

UHI generates greater convection
high rise buildings and mix of height increases turbulence and promotes vertical motion of air
produce large amounts of water vapor from industrial sources including hygrosopic particles which attract water and encourage the formation of rain

Question 17

How is fog affected by the UHI

Answer 17

industrialisation increases fog formation
in the 1700s in London 20 fog days per year, as industry increases by the 1800 50 fog days per year
Howver UK clean air act resulted in decrease in smoke production and fewer fog days

Question 18

Why do the UHI affect fog

Answer 18

pollutants act as condensation nuclei and encourage the fog formation especially at night in HP conditions

Question 19

How does the UHI affect thunderstorms

Answer 19

increase in thunder storms as they develop in hot humid conditions and can be characterised by violent and heavy precipitation usually in late afternoon in summer

Question 20

How are thunderstorms produced

Answer 20

convection uplift in conditions of extreme instability resulting in formation of cumulonimbus clouds where updraught of air through cloud results in rapid cooling and condensation which releases further latent heat
a postive electrical charge builds up in cloud, when this is overcome there is a discharge to a negative charge which results in lightening
extreme heat generate rapid development of expansion which results in shock wave which reuslts in thunder