URBAN URBAN MICROCLIMATESMICROCLIMATES

Construction of cities lead Construction of cities lead to: to: Profound changes in the climate of a specific Profound changes in the climate of a specific localitylocality

Watch the video and answer the Watch the video and answer the following questionsfollowing questions

http://www.youtube.com/watch?v=t-sXHl3l-rM&safe=active

1. What is an urban heat island?1. What is an urban heat island? 2. What causes urban heat islands?2. What causes urban heat islands? 3. What problems can urban heat islands cause?3. What problems can urban heat islands cause? 4.What can be done to solve these problems?4.What can be done to solve these problems?

What do cities do?What do cities do?

They destroy the existing They destroy the existing microclimate and create microclimate and create new ones.new ones.

There are three There are three processes involved:processes involved:

1. production of heat1. production of heat 2. alteration of land 2. alteration of land

surfacesurface 3. modification of the 3. modification of the

atmosphereatmosphere

PRODUCTION OF HEATPRODUCTION OF HEAT

Combustion of fuelsCombustion of fuels Release of heat Release of heat

stored in city’s stored in city’s brickwork and brickwork and concreteconcrete

Creation of ‘urban Creation of ‘urban heat island’heat island’

Altlanta urban heat Altlanta urban heat islandisland

Urban heat profileUrban heat profile

Another urban heat Another urban heat profile!profile!

Urban temperature Urban temperature transecttransect

ALTERATION OF LAND ALTERATION OF LAND SURFACESURFACE

Buildings and streets Buildings and streets can change wind can change wind speedsspeeds

Other urban variables to Other urban variables to consider:consider:

Wind velocities can vary Wind velocities can vary very locally in urban very locally in urban areasareas

Wind velocities can be Wind velocities can be increased!increased!

MODIFICATION OF THE MODIFICATION OF THE ATMOSPHEREATMOSPHERE

Air pollution reduces Air pollution reduces sunlight sunlight

Development of Development of smog smog

Calm conditions with Calm conditions with descending air and descending air and warm pollutants warm pollutants rising create an rising create an inversion layer.inversion layer.

Los Angeles inversion Los Angeles inversion layerlayer

Increase in Increase in condensation nuclei condensation nuclei leading to fogleading to fog