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Greenhouse gases and climate change
Published in Abhishek Tiwary, Jeremy Colls, Air Pollution, 2017
where V0(λ) is the solar flux at zero airmass at wavelength λ, Vm(λ) is the measured solar flux, τatm is the total optical depth of the atmosphere, and m is the airmass factor, expressed as 1/cos (zenith angle). Typically, the measured optical depth is the sum of several components, including those due to Rayleigh scattering and gaseous absorption; these are measured or calculated and the aerosol component obtained by difference. Measurements at many wavelengths enable the spectrum to be inverted and the particle size distribution to be calculated. The size distributions of aerosol from volcanoes such as Pinatubo have been modelled by formulas such as:
Air pollution and climate change
Published in Abhishek Tiwary, Ian Williams, Air Pollution, 2018
where: V0(λ) is the solar flux at zero airmass at wavelength λVm(λ) is the measured solar fluxτatm is the total optical depth of the atmospherem is the airmass factor, expressed as 1/cos (zenith angle)
Impact on solar radiation parameters in India during COVID-19 lockdown: a case study
Published in International Journal of Sustainable Energy, 2021
S. M. Revathy, A. G. Rangaraj, Y. Srinath, K. Boopathi, A. Shobana Devi, K. Balaraman, D. M. Reddy Prasad
When we consider the Sun Photometer’s output: Aerosol Optical Depth (AOD) is calculated from the atmospheric spectral transmission measurements. According to Bouguer-Lambert–Beer law, the sun irradiance E(λ, z) can be obtained at an altitude z above sea level at a given wavelength λ as where E0(λ) is the extraterrestrial sun irradiance, tg(λ, z) the gaseous transmission; m is the air mass given by 1/cos(θz) while considering airmass refraction and curvature of the atmosphere is neglected; θz the solar zenith angle and τ(λ, z) is the total optical depth of the atmosphere. Here E(λ, z) is the proportion of the Direct normal Irradiance we receive. Hence, the measurement of this quantity will explain the current situation of the atmosphere.
Design principles and radiometric calibration of a ground-viewing radiometer for automated vicarious calibration
Published in Journal of Modern Optics, 2020
Xionghao Huang, Xin Li, Xiaobing Zheng, Wei Wei, Haidon Xu
Under fair weather, the irradiance incident on the panel and normal to the radiometer, Epanel, is given by where E0λ is the exoatmospheric solar spectral irradiance, m is the airmass, σ is the spectral optical depth for a vertical path, Tgas is the transmission due to gaseous absorption, θ is the solar zenith angle, and Esky is the diffuse sky irradiance [6]. The diffuse irradiance is obtained when the direct solar irradiance is shaded. The band-averaged reflected radiance caused by direct solar irradiance that reflects the diffuse irradiance subtracted from the total component is given by where all variables are approximately as previously defined but are band-averaged and ρcλ is the band-averaged BRF of the panel [10]. The radiometric calibration coefficients, Ci, are expressed as where Vdirect is the band-averaged signal of the radiometer caused by the direct solar radiance reflected from the panel. The calibration coefficients of the three methods are shown in Table 3.