Unit 4 Flashcards
What is a microclimate?
is a distinctive climate that exists in a localised area, such as a city ( the climatic characteristics in this local area will differ from the prevailing regional conditions)
What are the reasons for higher temperatures in urban areas?
darker surfaces, cement, brick, tar
A.C forces hot air outside
What are the reasons for low humidity in urban areas?
low number of trees, so there is less evapotranspiration as drainage systems get rid of rainwater
What is the reason for fewer frosts in urban areas?
heating, and darker surfaces absorb heat
What are the reasons for more air particulates (dust) in urban areas?
particulates are released from cars, creates high levels of precipitation
What are the reasons for higher rainfall levels in urban areas?
more condensation nuclei, to form precipitation, air pollution and warmer temperatures
Since what year has more of the world’s population lived in urban areas than rural?
2010
By 2050, it is predicted what % of the population is predicted to live in urban areas?
70%
What is the definition of a megacity?
those cities with more than 10 million inhabitants
In 1950, how many Megacities were there and what were they called?
2, New York and Tokyo
How many Megacities where there in 2018?
37
What is an example of a developing megacity?
Dhaka in Bangladesh
When did Bangladesh gain independence and what was the population of Dhaka?
March 1971
pop of 250,000
economic growth and rural poverty
What proportion of the population in Dhaka are housed?
1/3
How much does traffic cost the city of Dhaka annually?
$2 billion
What particular issues of urban climate do cities like Dhaka face?
flooding
What is the meaning of Urban heat island?
urban areas are warmer than surrounding rural areas thus creating a localised warm area
What are the main causes of urban heat island?
- limited surface water, bare earth
- less vegetation
- decreased albedo (reflectivity)
- low surface water = less latent heat
What is the proportion of Asphalt reflectivity compared to grass?
Asphalt = 0.05 - 0.2
Grass = 0.25 - 0.3
Why do urban areas trap more heat than rural areas?
they have less vegetation and low albedo, which means heat is retained overnight
However, rural areas have more albedo and higher albedo and high surface water = latent heat, which is cooler
What is the case study for Urban heat islands?
Birmingham
By how much have temperatures risen over the last 15 years in the rapidly growing cities of New Delhi and Mumbai?
temps in both cities have risen 2-3 degrees in only 15 years
Nasa satellites show the cities being 5 - 7 degrees warmer than surrounding rural area
Why do high pressure anticyclonic systems lead to a more pronounced temperature difference between an urban and rural area?
air is sinking, which means there is a small pressure gradient
because it doesn’t rain sun provides insolation which increases the temp
When does the heat island affect become more pronounced?
between 5 and 6pm, until morning