119 week 8 Flashcards

1
Q

ways that humans modify small scale climate through surface conditions

A

albedo
altering geometry
mulching
moisture control

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2
Q

ways to alter near surface atmospheric conditions to control frost

A

preventing heat loss
adding heat
redistributing heat within the system

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3
Q

ways that humans modify small scale climate

A

change surface conditions
control for frost (near surface)
control fog conditions by adding and redistributing heat
control wind with barriers

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4
Q

Human modifications change what properties?

A

Radiative properties (K,L)
moisture properties (water, QE)
thermal properties (conductivity, QH)
Momentum (wind)

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5
Q

what does albedo regulate?

A

K (important for radiation and heat)

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6
Q

what does high albedo mean?

A

high perfection of K is reflected back

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7
Q

how can you change geometry to control radiation? what are some examples/

A

affects shortwave radiation absorption and long wave emission
- ridge and furrow induces multiple reflection, long wave emission reduced because sky view factor is lower (reduces cooling)
- receives energy at a more perpendicular angle

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8
Q

Ways that surface geometry affect radiative exchanges

A
  • insolation of a flat surface
  • insolation on a sloped surface, angle of incidence and multiple reflection (effective albedo)
  • long wave emission from a sloped surface, sky view factor influences total emission
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9
Q

how can solar collector be altered to maximize solar energy depending on the season?

A

in the winter when the sun is low, a more upright solar collector will have a more perpendicular angle of incidence with the solar beam

In the summer when the sun is high, a more horizontally positioned solar collector is best

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10
Q

what is aerating?

A

covering the surface layer with hay, woodchips, gravel, or other material with relatively large amounts of airspace. Air has a lower energy conductivity than bare soil, so air passes less energy to other objects.

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11
Q

what are the three ways that mulching controls evapotranspiration and soil warming

A

aerating
lowering albedo
conductivity

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12
Q

how does mulching change the conductivity of soil?

A

Covering the surface with material that has lower conductivity than the soil (i.e.,
paper). Even paper with similar albedo as bare soil can mediate temperature
fluctuations because it inherently has a lower conductivity than the soil

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13
Q

when is mulch laid down? why?

A

To prevent soil freeze, mulch is laid down in autumn to trap in subsurface heat (QG) throughout the winter. However, it must be removed in spring to allow input of
insolation during the warm season.

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14
Q

when does frost occur?

A

Frost occurs when surface temperature of the ground or plant falls below 0oC. Frost
control aims to keep temperatures at or above freezing

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15
Q

two types of frost

A

Radiative frost – due to radiative divergence.
Advective frost – due to a cold airmass horizontally transporting cold air into
the environment.

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16
Q

two ways to control frost

A

avoidance - do not put cold sensitive plants in cold places (regions where the air stagnates)
modification of the radiation and thermal energy balances

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17
Q

When does frost tend to occur?

A

at night under cold clear conditions (stable)

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18
Q

how do you control fog by altering energy conditions?

A

increasing turbidity
- to slow down energy loss from the system. This includes
Intentionally creating fog, smoke, or mist layers that increase atmospheric
absorptivity and sensible heat released toward the ground
increasing QH
- increasing QH with heat lamps. This is most effective when there is an inversion
layer that keeps warm air from rising and being replaced by sinking cooler air
redistributing QH
- Redistributing QH to the surface with fans. This method creates a vertically
mixed layer of moderate temperature. The rising hot air is brought back down

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19
Q

what does creating clouds of fog do?

A

creating clouds of fog or mist, or smoke reduces nocturnal loss of Lup, especially when the
atmospheric window is wide open. This reduces the sky view factor by placing a “radiative screen”
above the surface that closes the window. This is done using smudge pots, as well as cheesecloth
and glass pots.

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20
Q

why do they use heaters on orchards?

A

Orchards may use heaters to increase QH content. The impact of heating is restricted to the foliage
and fruit due to upward convection of the heated air. To bring QH back down, the use of heaters
may be combined with fans

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21
Q

When does Radiative frost occur? The

A

under inversion conditions.
aim then is to bring the warm air to
the surface by increasing the turbulent mixing and thereby enhancing the QH flux to the surface.
Large fans (i.e., windmills) are useful.

22
Q

fog is created through the ______________ process

A

condensation

23
Q

how does increasing QH, Mechanical mixing and seeding control fog

A

with heaters increases the moisture storage capacity of the air and causes the fog to dissipate.

by fans redistributes relatively dry air from higher elevation
down to mix with the fog layer and decrease the moisture concentration in the air

Cold and warm fog may be dispersed by seeding the fog with hygroscopic nuclei,
which promote cloud formation so much that fog droplets grow and fall out as rain.

24
Q

how do barriers effect wind?

A

barrier obstructs
progression of surface wind,
which causes the wind flowing
over the barrier to sink, as there
is nothing holding it up. This
creates vertical eddies
(turbulence).
Thus, there is a sharp decrease
in windspeed immediately
downwind of the barrier (aka
the ‘cavity’).
The barrier also promotes zero-
plane displacement (top of the
barrier / bottom of the
displacement zone).

25
Q

what are the two main ways that greenhouses modify the environment to make conditions more favorable to plants ?

A

radiative filters and wind shields

26
Q

how do greenhouses act as a radiative filter?

A

glass causes attenuation of 15-50%
therefore, K inside greenhouse is 85% - 50% of that outside the greenhouse

glass absorbs long wave radiation (coming in and going out), so its gets trapped in the greenhouse —>

L* is larger in a greenhouse than outside

27
Q

what happens to K and L at night in a greenhouse

A

at night, K is negligible outside and L* drops a lot but in the greenhouse K is still negligible but L* remains much larger, escapes at a rate less than 10% of the open air

28
Q

how do greenhouses stay balanced even though they aren’t letting out enough L* and therefore have a lot of Q*

A

must be balanced with large amounts of QH and QE
- temp gradients between greenhouse vegetation and the glass is lower than outside vegetation and the sky

29
Q

during the day, where is heat transferred in a greenhouse? at night?

A

into the soil, At night, when K* and L* decrease and temperatures begin to cool, the soil heat flux
is negative (aka heat leaves the soil) and replaces the heat lost via conduction
through the glass.

30
Q

ways to cool greenhouses down during the day:

A

ventilation: fans,
windows, Other methods of cooling include painting
the glass, putting straw on roofs, and more.

31
Q

is there a strong or weal vertical temperature gradient in a greenhouse? Why?

A

there is a strong vertical temp gradient because the walls block the wind and cause a zero plane displacement and prevent forced convection. Therefore, the air of a greenhouse does not mix

32
Q

what do builders consider exchanges between when trying to create a comfortable inside environment ?

A
  1. The external climate and the building.
  2. The building shell and internal living space.
  3. The living space and the occupants.
33
Q

what is the added aspect of climate in a building

A

QF = anthropogenic heat flux

ΔQS is the net change of energy storage
by the building and enclosed air.

QG (fka soil heat flux) is the energy
exchanged between the building and the
underlying ground.

34
Q

In the northern hemisphere, ___________ slopes receive less shortwave (K)
radiation, and the proportion of diffuse (D) versus direct (S) shortwave radiation is relatively large.

A

north-facing

35
Q

_________ slopes receive more shortwave energy overall, especially
during summer. The proportion of D to S shortwave radiation is
relatively low.

A

South-facing

36
Q

The angle of incidence depends on the ___________ and ____________
angles of the surface.

A

vertical (zenith), horizontal (azimuth)

37
Q

the temp of a wall is a function of the walls

A

aspect, which direction the wall is facing
time of day, which determines location of the sun and whether the wall is facing it

38
Q

the internal building temp is a function of what?

A

the walls temp, thus also a function of of aspect and time of day

39
Q

buildings often have negative _________

A

net longwave radiation fluxes

40
Q

What does QF come from ? What is QF’s relationship to external air temp?

A

QF comes from space heating, metabolic human and animal releases, and more.

QF has a direct inverse relationship with external air temperature.
QF increases as external temperature decreases, and vice versa

41
Q

characteristics of QH in relation to buildings

A

QH losses occur convectively and depend on wind speed and the temperature gradient between the building and the surrounding air.

QH is almost always directed away from the building. However, some heat is
conducted into the building through windows and walls.

42
Q

QE and QG in relation to buildings

A

QE is usually small, except after rain or if there are indoor plants (moisture release through transpiration).
QG depends on each buildings’ ground contact, thermal properties, and
temperature gradient between the floor and the ground.

43
Q

energy balance of room depends on

A

The level of interaction between:
o The room’s interior.
o The larger building overall, connected by the doors (open vs closed) and
uninsulated interior walls.
o The building’s exterior, connected by windows that allow greater exchanges
of K and L. Rooms facing toward the sun (i.e. southward in Los Angeles)
have greater solar heating through the windows and walls.

44
Q

How do places with intense humidity like Madagascar and Polynesia balance indoor climates ?

A

hut shape made of wood, piling structure, wattle, broad sloped roofs made of leaves

provides strong stable structure with abundant air flow

45
Q

how do they build homes in the mediterranean to adjust for the warm, dry summers?

A

thick brick, stone or. tuff to insulate from the outside

white. exterior for high rate of albedo

light wood roofs

few and small windows to minimize the exchange of heat with the exterior

46
Q

sandy desert environment conditions

A

extremely low moisture
low atmospheric turbidity
high surface reflectivity
total Q is small
QH is dominant
strong diurnal cycle
- temperature
- wind

47
Q

water dominated environment

A
  • high moisture
  • high atmospheric turbidity
  • high surface reflectivity

Total Q is large
- QE is proportionally large
- Mild diurnal fluctuations

48
Q

vegetated forest environment

A

tree canopy creates a new layer (low effective albedo, moisture source)

surface level:
low K
low QH
high moisture accumulation
zero-plane displacement

49
Q

variable terrain environment

A

slopes alter solar heating
- Perpendicular angle of
incidence cause warming.
* Aspect is important.
Valley
* Diurnal wind circulation.
* Katabatic vs Anabatic
Canyon effect
* Low effective albedo.
* High QH.

50
Q

indoor greenhouse environment chartcteristcis

A

greenhouse creates a new layer:
- high transmissivity to K
low transmissivity to L
Q* is large inside
Thus, QH/QE is large inside
- low wind
- accumulation of Q and moisture

51
Q

indoor non-greenhouse environment characteristics

A

buildings create a new layer
- low transmissivity
high absorption and emission of L
Total Q is regulated inside
- QE is low
- QH changes with seasons
- QF is inverse QH

52
Q

urban environment characteristics

A

Buildings create a new layer:
* Urban canopy with canyons.
* Low effective albedo.
* Low QE.
* High QH.
* Zero-plane displacement.
* High QF.
* High pollution