L22 Urban Hydrology and Climatology Flashcards
1
Q
What differences distinguish urban climates from those of less build-up areas?
A
- air temp
- humidity
- wind speed and direction
- air quality
- precipitation (quantity and where water goes)
2
Q
What are the differences in urban and rural micro-climates caused by?
A
- human construction
- release of artificially created energy into the environment
3
Q
urban wind observations
A
- calmer winds due to fricitonal effects of city’s vertical surfaces
- but some channeling/venturi effects
4
Q
temp observations
A
- warmer than surrounding countryside (URBAN HEAT ISLAND EFFECT)
- strongest at city centre
- difference of 2-8C btwn city and countryside
5
Q
Why Urban Heat Islands are formed
A
- urban surfaces have lower albedo (amnt of sunlight reflected by surface), greater heat conduction, more heat storage than surface they replaced
- building geometry (vertical surfaces( cause greater absorption of incoming solar radiation and outgoing infrared radiation
- human activities (transportation, industrial activity, heating of buildings)
- surface temps of urban structures 10-20C tighter than ambient temp
6
Q
What are Urban Natural Space
A
Evaporation, transpirtation and shades provide cooling
- waterbody, vegetation
7
Q
Natural Hydrologic Cycle
A
- evaportation, condensation, precipitation, tranpiration/respiration, runoff
- driving force = SUNLIGHT
- dissolved nutriends/wastes move and cleans parts of envrnmt, deposits contaminants in other parts
8
Q
Urban VS natural hydrology
A
Natural ground cover
- 50% infilitration
- 40% evapotranspiration
- only 10% runoff
Urban areas
- impervious surfaces limit infiltration and increase runoff
- fewer plants limit evapotranspiration
9
Q
Effects of increased runoff and reduced groundwater
A
- increased erosion
- flooding events more extreme
- degrade water quality
- lower groundwater levels btwn rainfall events
- less water available for urban vegetation
10
Q
Urban air quality
A
- increased electricty generation = higher GHG emissions
- summer heat islands accelerate formation of harmful smog ( produce ground level ozone)
11
Q
urban climate observations
A
- 10% more rainfall
- increased convectional uplift and particulate air pollution
- increase # of convection currents over urban surface
- condensation nuclei through air pollutions
12
Q
Permeable paving
A
- allow infiltration of storm water
- reduce runoff/flooding
13
Q
Bio-retention cells
A
- allow infiltration of storm water
- reduce runoff/flooding
- sol and vegetation perform water quality improvements
- shade trees reduce energy use
14
Q
Green Roofs Benefits
A
- reduce runoff
- improve water quality
- reduced energy consumption
- create habibtat to increase urban biodiversity
- protect roofing materials from sun degradation
- green amenity space
- improve air quality
- provide urban agriculture
15
Q
some other engineered solutions
A
- cool roofs (increased albedo/reflectance)
- green walls
- constructed wetland ( water treatment, increased vegetated space)
