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27 Cards in this Set
- Front
- Back
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canyon geometry |
stuff |
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Urban Heat Island |
Consequences of the UHI: - earlier budding of trees and plants - earlier blooming flowers - longer growing season - more birds stay during winter - warmth can be unbearable to humans (Heatwaves) greater user of air conditioning units - and therefore more energy used (anthropogenic heat flux), |
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sky-view factor |
stuff |
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convective instability |
when the temp at the surface is higher than points above the surface |
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evapotranspiration |
transpiration combined with evaporation, latent heat released |
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stomata |
cells of a plant that regulate the flow of CO2 and H2O; open during day, closed at night |
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active surface |
the main site of mass, heat and momentum transfer (elevated in a forest) |
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zero-plane displacement |
the apparent level of bulk drag exerted by vegetation on air level at which momentum is absorbed (it's an area right under the active surface where wind gets down to) |
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land/sea breeze |
water is cooler by day than night; horizontal temperature change leads to a change in pressure distribution so breeze during day is sea--> land; breeze during night is land--> sea |
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valley breeze |
daytime: anabatic up the valley (upslope wind)
nighttime: katabatic down the valley (downslope wind) |
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multiple reflection (shortwave) |
incoming shortwave radiation strikes on surface and is reflected onto another then another |
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frost |
when surface temperature of the ground/plants falls below 0 C |
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radiative frost |
due to radiative flux divergence |
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advective frost |
due to a cold airmass moving in |
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shelterbelt |
when humans modify horizontal wind speed near ground by erecting/planting barriers to wind (structures or trees) |
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QF |
anthropogenic heat flux due to space heating/cooling, metabolic human and animal releases |
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inadvertent climate modification |
clearest signs by urban regions b/c urbanization changes radiative, thermal, moisture, and aerodynamic characteristics of a region |
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urban boundary layer |
internal boundary layer that develops downwind from the leading edge of a city |
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urban canopy layer |
layer beneath roof level of city |
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urban heat island |
the temperature difference between air in the city and air in rural areas (city air is warmer) |
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air pollutants |
substances which when present in the atmosphere under certain conditions are injurious to humans and animals |
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advection |
horizontal flow/transport of energy warm air masses settle over cold, trapping polution |
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smog |
when turbulence produces a homogeneous mix of pollutants in the boundary layer |
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Vegetative surfaces: complicated by plants, so... |
1.) energy/ water stored in vegetation: store heat, energy, waterphotosynthesis/carbon dioxide 2.) exchange: net sink for CO2! (stomata are important for this, evapotranspiration) 3.) effect of stand architecture: higher active surface, less K gets to the ground; also reduced windspeed |
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Frost Strategies |
1. avoidance of cold areas 2. Radiation control: smoke to reduce sky view factor, increase longwave radiation absorbed 3. soil heat control: add water or soil to increase thermal conductivity 4. latent heat control: mist plants so water freezes and releases latent heat to warm plants 5. sensible heat control: use fans to create vortex (convection) to mix warm air down to the surface 6. direct heating: heaters for radiation and convection 7. fog clearance: mix in warm fog to make it rain |
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How to modify radiative budget.... |
1.) change albedo (changes amount of K that is absorbed) 2.) change geometry: surface angle and aspect (multiple reflection and sky view factor) 3.) thermal properties… a.) mulching: reduced evapotranspiration and enhanced soil warming (increase insulation to conserve heat loss) b.)irrigation/flooding: for more moisture and to increase thermal diffusivity, enhance evaporation |
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What wind barriers do... |
1. radiation budget not altered much 2. reduced QE and QH because less turbulence (less convection) 3. increase precipitation 4. increase dew formation 5. increase soil moisture storage |
