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286 > Urban climate - lectures 16-19 > Flashcards

Urban climate - lectures 16-19 Flashcards

1
Q

Landscapes modified by human agency, buildings

A

Urban environment

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2
Q

The localised warming exerted by an urban area

A

Urban Heat Island

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3
Q

Heat added to the atmosphere by human activities

A

Qf

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4
Q

Road transport, power generation, domestic heating, air conditioning

A

Examples of Qf

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5
Q

Heat stored within the urban canopy

A

Qs

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6
Q

Advection (from surrounding areas)

A

Qa

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7
Q

Is Qe important in UHI

A

less important - little surface water available for transpiration and evaporation. For local climate with parks or irrigated areas may cause oasis effect!

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8
Q

Is Qg important in urban areas

A

Yes, an enhanced role

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9
Q

Why is Qg more important in urban areas

A

Increased heat storage during the day caused by urban materials, increased heat emission in evening and night, low sky view factors

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10
Q

Where is Qg less important

A

Mediterranean settlements

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11
Q

What heat flux is most important in suburbs

A

Qh

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12
Q

Suburban Qh lags rural Qh

A

diurnal variation

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13
Q

Urban radiation & energy fluxes lead to the generation of…

A

urban boundary layer

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14
Q

Multiple reflective surfaces (urban canyon), changed albedo, particulate matter - reflects and absorbs incoming SW radiation

A

SW radiation

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15
Q

Particulate matter reflects and absorbs incoming SW radiation, as a result is a source of downwards LW radiation, reduced LW emission (sky view factor)

A

LW radiation

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16
Q

Additional source of energy Qf, reduced Qe, increased Qg and Qs, reduced Qa

A

Surface energy balance

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17
Q

High Qh and Qs, low Qe

A

City centre energy balance

18
Q

High Qe, low Qh and Qs

A

Rural energy balance

19
Q

Slower to warm up in mornings (Qg) and low sky view factors mean reduced receipt of SW radiation

A

Urban cool island

20
Q

Urban areas often have slower heating and cooling rates than rural areas

A

Diurnal evolution of UHI

21
Q

Why are warming & cooling rates different?

A

Qg, outgoing LW radiation

22
Q

How are parks different from urban surroundings?

A

colour - albedo
water availability

23
Q

High proportion of available water

A

possible oasis effect Qe > Q*

24
Q

Only occurs when synoptic-scale pressure gradients light, more common at night, can be of great significance for pollutant dispersal

A

Urban breeze

25
Q

Increased drag and turbulence from urban surface results in a relatively deep zone of friction - reduced windspeeds in comparison to equivalent rural atmosphere

A

Urban Boundary Layer

26
Q

if wind is oblique to street =

A

corkscrew effect

27
Q

if wind is parallel =

A

no sheltering by buildings - channelling of wind may result in jetting effect so enhanced wind speed

28
Q

Speed increases with height, so tall buildings will deflect faster moving upper air down to ground level, so can be up to 3 times windier than over open ground

A

Impacts of tall buildings

29
Q

Weak synoptic flow / pressure gradient, clear skies, more prominent at night

A

Favourable synoptic conditions for UHI

30
Q

City located on a high mountain ridge, prone to UHI development - UHI > 11°C recorded. Entrainment of warm urban air into katabatic flow makes some valleys warmer than valley heads.

A

Johannesburg, South Africa

31
Q

Since mid 1970s, greater diurnal temp on _____ and ____ compared to rest of the week

A

Sunday and Monday

32
Q

small town east of Chicago, downwind of steel mills, with increased annual precipitation from 990 mm to 1450 mm in 1930-1945. at nearby stations precipitation decreased from 990 to 900mm. rise in precipitation kinked to rise in steel production - but little investigation

A

The La Porte Anomaly

33
Q

positive correlation between UHI intensity and vapour pressure - so warmer nights associated with more moisture in air, difference in vapour pressure

A

Urban moisture excess (UME)

34
Q

Urban Plume - meso or micro?

A

Meso

35
Q

Canopy Layer - meso or micro?

A

Micro

36
Q

Line & point pollution sources

A

Canopy Layer/ microscale

37
Q

Areal pollution source

A

Boundary layer/ mesoscale

38
Q

Warm air overlying cold air

A

inversion

39
Q

occurs in a stable atmosphere, vertical motion is suppressed causing a relatively thin, concentrated plume

A

fanning

40
Q

occurs during the development of a surface radiation inversion

A

lofting

41
Q

If turbulent eddies are smaller than the pollutant cloud / plume

A

Will diffuse it

42
Q

if turbulent eddies are larger than the pollutant cloud / plume

A

Will transport it

286 (7 decks)

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