Part II: Radiation Flux Behavior and Observations Background Incoming and outgoi
ID: 3308281 • Letter: P
Question
Part II: Radiation Flux Behavior and Observations Background Incoming and outgoing shortwave (White) and longwave (Gray) describe the four fundamental types of radiation fluxes (see Figure 1, Pg.6) 1) Incoming shortwave radiation (SW) is the amount of global shortwave radiation received at the surface. It depends on location (e-g.. polar locations receive less direct sunlight), time of year (eg., sunlight is less direct in winter and more direct in the summer), time of day (e.g, sunlight is most intense around noon), cloudiness (which may reflect sunlight away before it reaches the surface) and other atmospheric conditions. Some of the solar radiation that reaches the surface is reflected away as outgoing shortwave radiation CSW . Note that this is not to be confused with the amount of sw reflected away (or absorbed or scattered) before it reaches the surface (4, by clouds). It depends on a surface characteristic known as albedo, which is dependent on the color and texture of the surface (eg, a white, snow covered surface has high albedo, resulting in relatively high SWT) As discussed above, the Earth emits its peak radiant energy at longer wavelengths than the Sun, known as outgoing longwave radiation (LW), which is dependent on temperature alone. Some of the outgoing longwave radiation is absorbed by the atmosphere and partially re-emitted back to the surface as incoming longwave radiation (LW·It depends on the condition of the atmosphere, especially cloudiness. 2) 3) 4) Note that the shortwave fluxes are only relevant from sunrise to sunset (no incoming solar radiation at night), but the temperature these fluxes impart on the Earth's surface results in longwave fluxes occurring all day long. Figures 2 and 3 (PE. 6 and 7, respectively) are graphs of shortwave and longwave radiation measured at the Earth's surface at Maun, Botswana, but for simplicity we will assume they were measured in Norman, OK. You will also be asked to interpret the meaning of net radiation, which is the sum of all four radiation types, shown as an example in the context of temperature in Figure 4 (pg. 10) at Boulder, CO. Important: Net radiation is equal to absorbed minus emitted shortwave radiation plus absorbed minus emitted longwave radiation. In equation form: Net radiation. (sww-sw)+(LW . LW) Net radiation·(Net Solar Radiation) + (Net Earth Radiation) If net radiation is negative, the Earth is losing more energy than it gains, and thus, the temperature is decreasing: If net radiation is positive, the Earth is gaining more energy than it loses and thus the temperature is increasing.Explanation / Answer
Over 99% of the energy flux raduated by the sun lies in the range from 0.15 to 4 micrometre. Approximately 50% lies in the visible region from 0.4 to 0.7 micrometre. The solar spectrum peaks at 0.49 pm, the green part of the visible portion.
About 99% of the radiation from the sun has wavelength in the range from 4 micrometre to 100 micrometre, in the thermal infrared portion of the electromagnetic spectrum. Wavelengths larger than 40 micrometre are usually neglected because of their small contribution, hence wavelengths only upto 50 micrometre are considered.