Blackbody temperature

Measurements show that the mean OLR from Earth is 237 W m-2 (Salby, 1996). Equation (1) indicates that our planet is then in thermal equilibrium at an effective temperature of 254.2 K. This blackbody temperature of the atmosphere is the effective mean temperature of Earth and its atmosphere. It corresponds to a shell-like layer of temperature, Te, surrounding the planet at a mean altitude of approximately 6.5 km. 

For the IRT 3000 a simultaneous calibration concept [6], that is shown schematically in Fig. 3.48, has been developed. At two different ambient temperatures two measurements at different blackbody temperatures are performed with completely assembled thermometers connected to external computers. This results in four independent sets of output values of both ambient and thermopile sensors (see Eq. 6 and 7) ... 

Black-and-white photography, fixation in, 19 213 Blackbody color of, 7 327 emittance from, 19 131-132 spectral radiance of, 24 453 Blackbody radiation law, 24 452 Blackbody responsivity, 19 132 Blackbody temperature sensor, 11 149-150 Black-box approach, to reliability modeling, 26 987-988, 990 Black copper, 16 144 Black crappie, common and scientific names, 3 187t... 

Temperature(s). See also Blackbody temperature sensor Cure temperature Curie temperature Eutectic temperature Fictive temperature Furnace temperature Glass- transition temperatures Heat entries Heating Hot entries Refrigeration Target temperature emperature measurement Thermal entries Thermo-entries Transition temperatures in analysis of water, 26 35 biofiltration system, 10 76 in biological wastewater treatment,... 

Fig 21 Blackbody Temperature - Time Plots For Two Bare Charge Shots... 

The most accurate measurements of the CMB spectrum to date have come from the Far InfraRed Absolute Spectrophotometer (FIRAS) on the COsmic Background Explorer (COBE) (Boggess et al., 1992). In contradiction to its name, FIRAS was a fully differential spectrograph that only measured the difference between the sky and an internal reference source that was very nearly a blackbody. Figure 9.2 shows the interferograms observed by FIRAS for the sky and for the external calibrator (XC) at three different temperatures, all taken with the internal calibrator (IC) at 2.759 K. Data from the entire FIRAS dataset show that the rms deviation from a blackbody is only 50 parts per million of the peak Iv of the blackbody (Fixsen et al., 1996) and a recalibration of the thermometers on the external calibrator yield a blackbody temperature of... 

A calorimetric method may be used where an electric heater is imbedded in the object of interest, and the power dissipated by the element is accurately calculated from voltage and current. Once steady state is established and the object is at constant temperature, the body must emit radiation at the same rate at which it is supplied. As long as conduction and convection are eliminated as mechanisms of heat transfer (e.g. vacuum conditions), the blackbody temperature is known by Rt = o"T4. The emittance can then be determined after py-rometric measurements of the brightness temperature of the object. 

If the radiant flux from the sun is 1350 W/m2, what would be its equivalent blackbody temperature ... 

It is quite apparent from Fig. 8-63 that solar radiation which arrives at the surface of the earth does not behave like the radiation from an ideal gray body, while outside the atmosphere the distribution of energy follows more of an ideal pattern. To determine an equivalent blackbody temperature for the solar radiation, we might employ the wavelength at which the maximum in the spectrum occurs (about 0.5 /im, according to Fig. 8-63) and Wien s displacement law [Eq. (8-13)]. This estimate gives... 

FIGURE 4.6 The dependence of the intensity of blackbody radiation on wavelength for two temperatures 5000 K (red curve) and 7000 K (blue curve). The sun has a blackbody temperature near 5780 K, and its light-intensity curve lies between the two shown. The classical theory (dashed curves) disagrees with observation at shorter wavelengths. 

On a clear night, when the effective blackbody temperature of space is — 70°C, the air is at 15°C and contains water vapor at a partial pressure equal to that of ice or liquid water at 0°C. A very thin film of water, initially at 15°C, is placed in a very shallow well-insulated pan, placed in a spot sheltered from the wind with a full view of the sky. If = 2.6 W/m - C, state whether ice will form, supporting the conclusion with suitable calculations. 

Tm Blackbody temperature corresponding to the pyrometer-measured radiant energy, K... 

For an average blackbody temperature of the Earth-atmosphere system Te defined on the basis of (4.4), the longwave emitted flux averaged over the globe is... 

In summary, the net outgoing radiative flux of about 235 Wm-2 corresponds to a blackbody temperature of 255K (—18°C). The surface emission of 390Wm-2 corresponds to a blackbody temperature of 288 K. Therefore, the surface temperature is about 33°C warmer than it would be if the atmosphere were completely transparent (and the planetary albedo were still 0.3). 

Figure 23.11 shows a way to view the greenhouse effect. The mean atmospheric temperature profile is shown starting from the current mean surface temperature of 288 K. If we assume a global average rate of decrease of temperature with height of 5.5 K km-1, the temperature of 255 K, the blackbody temperature corresponding to the mean emitted... 

Blackbody Temperature-Time Plots for Two Bare Charge Shots. S 76... 

The mean emitted power of the Earth-atmosphere system, 240 W corresponds to a blackbody temperature of 255 K. The surface emission, 390 W m, corresponds to a blackbody temperature of 288 K. The 33 K difference between the blackbody temperatures of the Earth s surface and the Earth-atmosphere system is the so-called greenhouse effect. Increases in concentrations of CO2 and other GHGs since the Industrial Revolution are estimated to have contributed about +2.5 W m to the global and annual average radiation balance (IPCC, 1995). 

Interaction of blackbody radiation with Rydberg atoms was first studied by Gallagher and Cooke, and by Belting et The dependence of this interaction on radiation exposure time and blackbody temperature was investigated by Koch and co-workers. ... 

A building s flat black roof has an emissivity of 0.9, along with an absorptivity of 0.8 for solar radiation. The sun s energy transfer is 946 W/m. The temperature of the air and surroundings is 26.7°C. Combined conduction-convection heat transfer is given by q/A — 0.38(A7 ) where the AT is the difference between the roof and the air. Find the roof temperature (assume that the blackbody temperature of space is —70°C). 

The effective blackbody temperature of the outer atmosphere on a clear night is —70°C. Air at 15°C has water at a vapor pressure equal to liquid water or ice at 0°C. If a thin film of water is placed in a sheltered pan with a full view of the sky, will ice form Assume that the convective h is 2.6 W/m C. 

Windows (b) and (c) above supply, after calculation of the radiation received, radiance temperatures different from their real temperatures. As we will have occasion to see, the real temperatures have considerable effect on the radiance temperatures, which we will often term equivalent blackbody temperatures. 

Fig. 8. Effective radiance curves, equivalent blackbody temperatures. (High resolution infrared radiometers, Nimbus 2, Nimbus 4, and Nimbus 5.)...

Relationship between real temperatures and equivalent blackbody temperatures... 

The role of emissivity, although a logical one, is often underrated. Some investigators are trying at all costs to find the exact temperatures of oceans from the equivalent blackbody temperatures obtained by satellite observations. To do this they go into sophisticated correction calculations adding, as the case may be, 2°, 3°, 5°, or 10 K, and compare their results with those of marine researchers who dip a thermometer into a bucket of seawater (in fact, these corrections are calculated in order to make... 

Fig. 24. Radiance temperatures in the region of the Aral-Caspian Seas. - Nimbus 2, nighttime channel, 3.5-4.2/rm orbit 1498, 4 September, 1966. 7 bb = equivalent blackbody temperatures (radiance temperatures).

The most convenient calibration sources for the middle and far infrared are black-bodies at constant and well-known temperatures. The range of blackbody temperatures should match approximately the range of expected brightness temperatures of the planetary atmospheres and surfaces under investigation. Of course, calibration sources are also subject to systematic errors the temperature sensor of a blackbody may be systematically off, or the actual emissivity of the device may not be as close to unity as assumed. However, these types of error generally can be kept small in number and in magnitude in comparison with systematic changes of the instrument response. 

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