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Fundamentals of Solar Radiation
Published in D. Yogi Goswami, Principles of Solar Engineering, 2023
Various types of high-resolution radiometers collect radiative data images of the earth’s atmosphere below. These radiometers scan spectral measurements in the wavelength ranges of shortwave (0.2–3.0 μm), longwave (6.5–25 μm), and total irradiance (0.2–100 μm). The spatial resolution of images from the satellite is given by a pixel, which represents the smallest area of data, generally of the order of 2 km × 2 km. However, several pixels of data are required to derive a surface value giving a surface resolution of the order of 10 km × 10 km. Figure 2.29 shows an example of an intermediate resolution GOES-8 image around Albany, New York, overlaid on a local map.
Solar water heating
Published in John Twidell, Renewable Energy Resources, 2021
These are constructed with geometric or rough surfaces that trap shortwave irradiation by multiple reflections within cavities of scale ∼0.5 µm, so giving large shortwave absorption. However, longwave irradiation of wavelength ∼10 µm is not so absorbed in such small cavities, so, by Kirchhoff's law, the longwave emittance is small. The construction is therefore a selective absorber. Moreover, the textured surface can be designed to have directional characteristics if needed.
Radiometer Calibrations
Published in Frank Vignola, Joseph Michalsky, Thomas Stoffel, Solar and Infrared Radiation Measurements, 2019
Frank Vignola, Joseph Michalsky, Thomas Stoffel
Longwave radiation is measured with a pyrgeometer designed to detect IR irradiance over the wavelength range of approximately 4–50 µm. This section provides a brief introduction to the concepts of pyrgeometer design, the use of blackbody calibrators, the development of an internationally recognized reference measurement standard for downwelling infrared irradiance, and the recent advances in instrument design that could lead to an improved reference measurement standard for this important form of radiation.
Variability and trends in land surface longwave radiation fluxes from six satellite and reanalysis products
Published in International Journal of Digital Earth, 2023
Jianglei Xu, Shunlin Liang, Tao He, Han Ma, Yufang Zhang, Guodong Zhang, Hui Liang
SLR flux values from satellite-derived and reanalysis products generally represent the surface longwave radiation energy within a spectral range of 4–100 µm. Although the spectral response function of pyrgeometers typically covers a wavelength of 3.5–50 µm, its reading is calibrated to the total range of terrestrial longwave emission (∼4–200 µm) (Wang and Dickinson 2013). Therefore, it is reasonable to directly utilize ground measurements to validate SLR flux data from satellite and reanalysis products. The 288 ground sites are distributed across different elevations up to ∼5000 m in Qinghai-Tibet Plateau (TP) region (172: 0–1000 m, 19: 1000–2000m, 4: 2000–3000 m, 6: 3000–4000 m and 2: 4000–5000 m). Regarding land cover types, these sites are distributed in forest (91), shrubland (19), grassland (68), wetland (15), cropland (35), snow/ice (48), and barrenland (3). Moreover, the sites are also located in different climate zones, including tropical (25), dry (21), temperature (72), continental (101), and polar (49). Therefore, ground measurements from the 288 sites ensured a comprehensive assessment of the six satellite and reanalysis SLR flux products.
Two-dimensional internal gravity wave beam instability. Linear theory and subcritical instability
Published in Geophysical & Astrophysical Fluid Dynamics, 2021
In figure 7, the Henrici number is shown for as a function of θ and . Obviously, the figure is fundamentally different from figure 3(a) implying that normal-mode instability is not connected to the non-normality of the matrix. The pattern of the Henrici number as a function of θ and does not show the filigree structure of figure 3(a) but roughly shows three different regions: for shallow beams with longwave perturbations, for steep beams with longwave perturbations, and for beams of all angles with shorter wave perturbations. As mentioned above, oblique beams play an important role with respect to the buoyancy profile of the stratosphere. We see that a wide range of low-frequency longwave perturbed beams have the potential to show subcritical instability whereas such beams are linearly stable (see figure 3(a)).
The global response of temperature to high-latitude vegetation greening in a two-dimensional energy balance model
Published in Atmospheric and Oceanic Science Letters, 2020
Lu BI, Yongli HE, Jianping HUANG, Yaokun LI, Xiaodan GUAN, Xiaoyue LIU
where ρa is the atmospheric density; cp is the specific heat at constant pressure; cv is the specific heat at constant volume. T is the atmospheric temperature; R is the specific gas constant; p is the atmospheric pressure; ε1, ε2, and ε3 are the heat fluxes caused by the radiation, turbulence, and the condensation or evaporation, respectively. Let be the longwave radiation absorption coefficient for the wavelength , and be the average absorption coefficient for solar radiation. Aj (Bj) is the downward (upward) longwave radiation in the wavelength interval, Ej is the blackbody radiation within the wavelength interval. Q means downward solar radiation. Kh is the horizontal turbulent temperature coefficient; K is the vertical turbulent temperature coefficient; z is the altitude, and is the horizontal Laplacian, where both Kh and K are constant.