✅3.2.3.4 - Urban Climate Flashcards
What aspects of the climate can urban areas modify?
Wind speeds
Temperature
Clouds and precipitation
Pollution
In what ways can winds be modified by urban areas?
Lower speeds
Greater variability
Large-scale convection
Why are wind speeds generally lower in urban areas?
The roughness of the land surface, consisting of buildings at a variety of heights, creates greater surface friction
What is an urban canyon?
A street with tall buildings either side but a space in between
What is the Venturi effect?
The effect of ‘squeezing’ the airflow, increased as buildings get taller towards the city centre
Where is the highest air pressure?
In the upper part of the building with air flowing down the front and over the top
How does convection occur over urban areas?
Convection and uplift over the area means that air pressure is lowered and air is drawn in from surrounding rural areas
What is the urban heat island?
Urban areas are on average 1-2 degrees warmer than their surrounding rural areas
What is albedo?
The degree of warming of a surface depends on the amount of insolation absorbed by the surface, which in turn depends on how much is reflected. The reflection is albedo.
What is sky view factor?
The amount of sky you can see without your view being impeded by tall buildings
What is specific heat capacity?
The amount of energy required to raise the temperature of 1kg of a material by 1 Kelvin
What is the intensity of an urban heat island?
The maximum difference between the temperature of the rural area and the peak urban temperature
How can weather conditions impact the intensity of the urban heat island?
High pressure systems with clear nights and sunny days increase the intensity
What are the five main factors causing urban heat islands?
Anthropogenic heat
Height and arrangement of buildings
Nature of building materials
Presence of water
Pollutants
What is sensible heat?
Heat energy which can be felt, as opposed to latent heat which must be measured
