Geo Chp 4
What is the global energy budget and where do the deficits occur?
The average annual energy distribution is positive for Earths surface and negative for the atmosphere as it radioed energy into space. However, when considered together, these two equal each other, making it possible for us to construct an overall energy balance.
What is the daily radiation pattern?
The daily pattern of absorbed incoming shortwave energy and resulting air temperature.
What is the difference between how long-wave and shortwave radiation interact with clouds?
The effect of clouds is dependent on the percentage of cloud cover as well as cloud type, altitude, and thickness. Low thick stratus clouds reflect about 90% of insolation. High altitude, ice crystal clouds reflect only about 50% of incoming insolation. These cirrus cloud act as insulation, trapping long-wave radiation from earth and raising minimum temps
What do clouds or gases have to do with the greenhouse effect?
The effect of clouds is dependent on the percentage of cloud cover as well as cloud type, altitude, and thickness. Low thick stratus clouds reflect about 90% of insolation. High altitude, ice crystal clouds reflect only about 50% of incoming insolation. These cirrus cloud act as insulation, trapping long-wave radiation from the earth and raising minimum temps. Cloud-albedo forcing refers to an increase in albedo caused by clouds and the resulting cooling of earth surface. Cloud-greenhouse forcing is an increase in greenhouse warming caused by clouds because they can act as insulation, trapping longwave (infrared) radiation.
Explain what the surface energy budget is?
The energy balance in the boundary layer is affected by the specific characteristics of Earth's surface, such as the presence or absence of vegetation and local topography. The surface in any given location receives and loses shortwave and long wave energy according to the following scheme: SW↓- SW↑ + LW↓-LW↑= NET R SW↓= Shortwave Insolation SW↑= Shortwave Reacection LW↓= incoming Longwave Infrared LW↑= outgoing Longwave Infrared NET R= Net Radiation
What is the greenhouse effect?
The process whereby radiatively active gases (CO2, water vapour, methane, and CFCs) absorb and emit the energy at longer wavelengths, which are retained longer, delaying the los of inferred to space. Thus the lower troposphere is warmed through the radiation and re-radiation of infrared wavelengths. The approximate similarly between this process and that of a greenhouse explains the name.
What is albedo?
The reflective quality, or intrinsic brightness, of a surface.
Explain why the time lag occurs?
The warmest time of day occurs not at the moment of maximum insolation but at the moment when a maximum insolation has been absorbed and emitted to the atmosphere from the ground. As long as the incoming energy exceeds the outgoing energy, air temps continues to increase, not peaking until the incoming energy begins to diminish as the afternoon suns altitude decreases.
How do the three types of radiative heat transfer mentioned above differ, which is the most important?
Through the processes of latent, sensible, and ground heat transfer, the energy net radiation Is able to the work that ultimately produces the global climate system - work such as raising temps in the boundary layer, melting ice, or evaporating water from the oceans. Most important would be latent heat. H is the heat transferred back and forth between air and surfaces through convection and conduction. LE is the energy that is stored in water vapour as it evaporates. G is the glow of energy into and out of the ground surface by conduction.
What is the transmission of energy?
Transmission refers to the uninterrupted passage of shortwave & long wave energy through either the atmosphere or water.
What is Earth's average albedo?
31%
What is the albedo of asphalt when compared to grass?
5%-10% asphalt while grass is 25%-30%
What is refraction?
A change in medium occurs when insolation passes from air into water. Such transitions subject the insolation to a change of speed, which also shifts its direction. This is the bending action of refraction.
What is a dust dome?
A dome of airborne pollution associated with every major city; may be blown by winds into elongated plumes downwind from the city.
What controls albedo?
A variety of factors influence albedo. Darker colour surfaces have lower albedos while lighter coloured surfaces have higher albedos. On water surfaces, the angle of the solar rays also affects albedo. Lower angles produce more reflection than do higher angles. Smooth surfaces increase albedo, whereas rougher surfaces reduce it.
What is cloud greenhouse forcing?
An increase in greenhouse warming caused by clouds because they can act like insulation, trapping longwave (infrared) radiation.
Explain what the urban heat island effect is?
An urban microclimate that is warmer on average than area in the surrounding countryside because of the interaction of solar radiation and various surface characteristics. Generally 6° hotter than surrounding suburban and rural areas, mainly because vegetation is lacking.
What is energy absorption?
Assimilation and conversion of radiation from one form to another in a medium. In the process, the temp of the absorbing surface is raised, thereby affecting the rate and wavelength of radiation from that surface. Converted into either longwave radiation or chemical energy (photosynthesis).
Name three greenhouse gases
CO2, methane, CFCs
What three ways is this energy transferred?
Conduction, Advection, Convection
What is the difference between conduction and convection?
Conduction: The slow molecule to molecule transfer of heat through a medium, from warmer to cooler portions. eg. Touching a stove and being burned Convection: Transfer of heat from one place to another through the physical movement of air, involves a strong vertical movement. eg Hot air rising, cooling, and falling
When is it coolest?
Dips to its lowest point right at or slightly after sunrise
Why is the sky red and when does this occur?
Direct rays (from overhead) mass through less atmosphere and experience less scattering than do low, obliques-angle rays, which must travel farther through the atmosphere. When the sun is low on the horizon at sunrise or sunset, shorter wavelengths (blue and violet) are scattered out, leaving only the residual oranges and reds to reach our eyes.
What kind of energy is emitted from the sun vs. the earth?
Earth-atmosphere energy budget comprises of: shortwave radiation inputs (uv light, visible light, and near-infrared wavelengths) from the sun and longwave outputs (thermal infrared wavelengths) that pass through the atmosphere through the transmission to space from the earth.
When is it warmest?
Generally peaks between 3 and 4pm
What controls this effect?
Heating (in North America) is increased by modified urban surfaces such as asphalt and glass, building geometry, pollution and human activity such as industry and transportation. The removal of vegetation and the increase in human made materials that retain heat are two of the most significant UHI causes. Urban surfaces (metal, glass, concrete, asphalt) conduct up to 3 times more energy than wet sandy soil.
What is the difference between convection and advection?
Horizontal movement of air or water form place to another. eg Ocean currents are another example of advection heat transfer. Rather than vertically, currents move warm or cold water in horizontal directions. As these waters interact with warmer or cooler areas of water, heat is exchanged between them.
What is meant by the scattering of energy?
Insolation encounters increasing dense atmospheric gases as it travels towards earth surface. These atmospheric gases as well as dust, cloud droplets, water vapour and pollutants physically interact with insolation to redirect radiation, changing the direction of the lights movement without altering its wavelengths.
Discuss the global patterns of insolation?
Insolation or incoming solar radiation is the single energy input driving the Earth-Atmosphere system, yet it is not equal at all surfaces across globe. Consistent day length and high sun altitude produce fairly consistent insolation values throughout the tropical and equatorial latitudes. Insolation decrease toward the poles, from about 25° latitude in the both the N and S hemispheres. In general, greater isolation at the surface occurs in low latitude deserts b/c of frequent cloudless skies.
What is the latent heat of vaporization (evaporation) and what does it have to do with the global energy budget?
Is the energy stored in water vapour as water evaporates. Water absorbs large quantities of this latent heat as it changes state to water vapour, thereby removing this heat energy from the surface. Latent heat is the dominant expenditure of Earths NET R especially over water surfaces.
What is latent heat of evaporation (LE)
Is the energy that is stored in water vapour as water evaporates. Water absorbs large quantities of this latent heat as it changes state to water vapour, thereby removing this heat energy from the surface. This heat energy releases to the environment when water vapour changes state back to a liquid. Latent heat is the dominant expenditure of Earth's entire NET R especially over water surfaces.
What is ground heating (G)?
Is the flow of energy into and out of the ground surface by conduction. During a year, overall G value it zero because the stored energy from spring and summer is equaled by losses in fall and winter. In snow or ice covered landscapes most energy is in sensible and latent heat used in the melting and warming process.
What is sensible heat (H)?
Is the heat transferred back and forth between air and surface in turbulent eddies through convection and conduction within materials. About one fifth of earth's entire NET R is mechanically radiated as sensible heat from the surface, especially over land.
Why is the sky blue?
Light from the Sun appears white but it actually consists of many different colours. As the white light from the Sun travels through the Earth's atmosphere, it collides with particles of air. The different colours, or wavelengths, of light are scattered by these collisions by different amounts. Blue light (shorter wavelengh) is scattered more than red light (longer wavelength). So, when the Sun is high in the sky, blue light is scattered in all directions as sunlight passes through the atmosphere and we see the sky as blue.
When does the surface energy budget become negative (day or night)?
NET R values are positive during the daylight hours, peaking after noon with the peak in insolation; at night values become negative because the shortwave component ceases at sunset and the surface continues to lose long wave radiation to the atmosphere.
How do these differ with respect to ground covering (bare vs vegetated) and latitude?
On land, the highest annual values for LE occur in the tropics and decrease towards the poles. Over the oceans, the highest LE values are over subtropical latitudes, where hot, dry air come into contact with warm ocean water. Vegetated landscapes are able to retain much more of its energy because of lower albedo values (less reflection), the presence of more water and plants, lower surface temps.
What could you do to counteract the effects of the urban heat island?
Planting of vegetation in parks and open space (urban forests), green roods, cool roofs (high albedo roofs) and cool pavement (lighter coloured materials such as concrete or lighter coater surfaces for asphalt)
What kind of energy does this scattering produce?
Produces diffuse radiation. Weaker, dispersed radiation which is composed of waves traveling in different directions and thus casts shadowless light on the ground.
What is the name of the scattering principle?
Rayleigh scattering (shorter wavelengths are scattered more, longer wavelengths are scatted less)
What is cloud-albedo forcing?
Refers to an increase in albedo caused by clouds due to their reflection of incoming insolation.
What controls the ↓K (SW) and outgoing ↑LW?
Shortwave from the sun (both diffuse and direct) and long wave that is reradiated from the atmosphere after leaving earth. Energy losses include reflected shortwave and earths long wave emissions that pass through to the atmosphere and space.
Why is the sky red or orange when the sun is setting?
What's going on here is that as the sun is setting, the light you are seeing from it is having to travel through a lot more atmosphere given your angle to the sun. Light at lower wavelengths gets scattered more than at the higher wavelengths. So less of the blue light gets to you as it's being scattered more than, for instance, yellow, orange, and red. In this case, if it is a relatively clear day, the sky will appear more yellow than blue as you watch the sunset because the blue is being scattered so much it never reaches you or at least, not as much of it, but the yellow isn't scattered nearly as much but still scattered enough to make the sky look yellow.
Is it greater or lower at high latitudes and why?
Yes. Albedos average 19-38% for all surfaces between the tropic's. Albedos for the polar regions may be as 80% as a result of ice and snow (smooth, clear surfaces, low absorption).
