Presentation on theme: "Energy Budget of the Earth-Atmosphere System"— Presentation transcript:
1 Energy Budget of the Earth-Atmosphere System In the previous lesson you learned that the earth-atmosphere system is in radiative balance; we could also say that it is in energy balance, since the only form on energy that enters or leaves the system is radiation. You also learned that it is the “imbalances” of energy from place to place across the globe that account for atmospheric processes such as the circulation of the winds and ocean currents and that explain the pattern of climates on the globe.
2 Energy Transfer Conduction -- direct molecular transfer Convection -- fluids; air or waterSensible heat (temperature)Latent heat (evaporation/condensation)Radiation -- no transfer mediumBasic physics – three ways in which energy is transferred from place to place.
3 Adiabatic ProcessesThis term refers to the warming or cooling of air due to the rise or descent of air. Rising air cools as it expands; descending air wamrs as it compresses.
4 Just in case you need to understand that relationship between the three temperature scales – Kelvin, Celsius, and Fahrenheit.
5 This should be self-explanatory: the evaporation of water absorbs energy from the surrounding air; whereas condensation releases energy. The point is that these changes of state of water are significant in the transfer of energy.
6 Energy associated with phase changes A more detailed look at the same thing, for whatever it is worth.
8 All the energy that drives the environmental systems of the earth start with solar radiation.
9 The Sunspot CycleSunspots indicate constantly changing levels of solar activity; they have been monitored for centuries and there is some thought that they have impact on climate variability.
10 to the distance squared (inverse square law). As the distance from the Sun increases, the intensity of the radiation diminishes in proportionto the distance squared(inverse square law).The solar constant is the amount of solar energy received by a surfaceperpendicular to the incoming rays at the mean Earth–Sun distanceand is equal to 1367 W/m2.Solar constant – in whatever units – is a measure of the solar radiation reaching the top of the atmosphere, before it is depleted in its journey through the atmosphere.
12 Electromagnetic radiation can be discussed in terms of the wavelengths Electromagnetic radiation can be discussed in terms of the wavelengths. The only ones that are relevant to weather and climate are Infrared, Visible, and Ultraviolet
13 The electromagnetic spectrum shows this using the units of micrometers (mm), and it shows the breakdown within the visible portion of the spectrum
14 Radiation Laws Stefan-Boltzmann Law E = sigma T (4th power) Wien's Law:Wavlength Max - inversely proportional to the temperatureThese are the two basic laws of radiation and are well illustrated in the several slides that follow; you are also reading about these in the Ritter chapter.First, recognize that EVERYTHING emits radiation.The first law simply shows that the intensity of radiation emitted by anything is proportional to the temperature to the 4th power; so, the sun would emit radiation at a much, much higher rate than all the earthly things which are much, much cooler.The second law shows that the wavelengths of radiation emitted are inversely proportional to temperature. Hence, the very hot sun emits radiation in short wavelengths as illustrated on following slides and the earth/land/water/atmosphere emit radiation at much longer wavelengths because they are much cooler.Solar Radiation = also known as shortwave radiationTerrestrial Radiation = also know as longwave radiation (or infrared radiation)
19 This depicts that the gas nitrous oxide absorbs significant amounts of radiation in the longer wavelengths, and very rare in the shorter wavelengths.
20 Methane also absorbs significant amounts of radiation in the longer wavelengths.
21 Ozone, a version of oxygen with three molecules, is very, very important in absorbing radiation in the ultraviolet portion of the spectrum. It provides a life-protecting shield against the lethal effects of ultraviolet radiation.
23 Carbon Dioxide – the most important Greenhouse gas – absorbs large amounts of radiation in the longwave portion of the spectrum. That is it “traps” a lot of radiation emitted by the earth surface, and re-radiates back to the surface. This Greenhouse effect is tremendously important in maintaining the warm temperatures we know and love.
24 This shows all the gases combined This shows all the gases combined. You see here that much of the solar radiation is NOT absorbed in the atmosphere; rather, mcu of it passes directly on to the surface of the earth. In the infrared (longwave) portion of the spectrum, a much higher percentage is absorbed: The Greenhouse Effect! It is important to remember that the greatest amount of absorption is die to the presence of water vapor; it is indeed the primary Greenhouse gas.
25 There you go – no atmosphere, no protective layer of the atmosphere; and it would be really, really cold here – we would not be here.
28 the surface, of which another 5 units are reflected back to space. Incoming solar radiation available is subject to a number of processes as it passes through the atmosphere. The clouds and gases of the atmosphere reflect 19 and 6 units, respectively, of insolation back tospace. The atmosphere absorbs another 25 units. Only half of the insolation available at the top of the atmosphere actually reachesthe surface, of which another 5 units are reflected back to space.The net solar radiation absorbed by the surface is 45 units.Read and try to make sense of it – the distribution of solar radiation as it passes through the atmospere.
31 ALBEDO means reflectivity; the percentage of incoming solar radiation that is reflected back rather than being absorbed. Over water (Global oceans) the degree of reflectivity changes greatly depending on angle of the sun above the surface.
32 Bottom line, I guess. This is an older global climate graph; did you ever wonder what average global temperature really means, and how it is “measured.”