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Unformatted text preview: General idea 1. Conserving open forests, space, etc.- To develop plants and conserve and promote open space in urban areas ○ "Open Space" plans - Urban trees - Toronto 2. Suburbs hotter than downtown & more trees in downtown - More vegetation = away from red signal ○ Urban heat-up ○ High thermal mass effect ○ Vegetation associated from heat - Outline (implications) 3. Loss of cooling control Urban heat islands = "ghost of forests" ○ Tree cover and urban heat islands (UHI)- How does UHI affect weather? - How does UHI affect heat, health and income? - Urban heat island 4. Has been acknowledged for long time- UHI present in downtown London to outermost ○ First known phenology of an UHI ○ "Climate of London" (1833, Howard)- Urban vs. Forest ○ Surface of road: how much energy is stored? 1.2~2.0mm / day evaporation by tree □ Measured in actual amounts of water (1.6mm/day) How does this related to transpiration measure by trees? □ UHI & heat build-up due to loss of trees = loss of transpiration = loss of cooling! □ Evaporation of water (transpiration & cooling) measured in thickness When difference taken, heat average peaks in early spring - summer then peaks off ○ Nowadays, satellite used to measure UHI- Upward air mass flowing from UHI (bringing cold downward air mass) measured Heat island formed instability in the air, causing rainfall & thunderstorm Case of Atlanta ○ Lightening measured by National Lightening Detection Network ○ Upwind control has uniform pattern of rainfall. Urban area showed rainfall in the afternoon. Shows precipitation distribution affected by UHI during the day. Rain particle = water particle + dust particle □ More emission = more time it takes to develop rain fall □ Later in the day, the emission distribution affected (along with workweek) that is also associated with precipitation. Case of Houston ○ What are the consequences of loss of vegetation on weather? - UHI affecting health & socio economic issues 5. More income = greater tree cover ○ Income explains 45% in variation in tree ○ Able to plot income vs. tree cover- Lecture by Will Wilson - What good are urban trees? March-09-11 8:05 PM February 17 Page 1 Shows strong positive correlation between human & tree What is the value of trees? <-- very complicated as the "value" involves the ownership Low air quality = high ozone level = lack of cooling instruments (i.e. tile roof, swimming pool, air condition, parks, etc. = health problems (i.e. asthma) 25% reduction in aggression with "green" view Domestic violation / incidents of aggression...
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This note was uploaded on 06/20/2011 for the course EHJ EHJ351 taught by Professor Peterabrams during the Spring '11 term at University of Toronto- Toronto.
- Spring '11