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Fundamentals of Ocean Optics
Published in Victor Raizer, Optical Remote Sensing of Ocean Hydrodynamics, 2019
A branch of optics studying the behaviour of solar radiance in the Earth’s atmosphere is called atmospheric optics (Rozenberg 1966; McCartney 1976). This includes both understanding naturally occurring optical effects and interactions between electromagnetic radiation (sunlight) and atmospheric constituents. Vertical structure of the Earth atmosphere is shown schematically in Figure 3.11. According to standard nomenclature, the vertical profile is divided into four distinct layers known as troposphere, stratosphere, mesosphere, and thermosphere (and also fifth layer known as exosphere). Optical wave propagation and radiation in cloudiness atmosphere is defined by the following major factors: Profiles of temperature and pressureProfiles of oxygen, water vapor, and cloud liquid water concentrationsFluctuation of the index of refractionMolecular absorption by atmospheric gases (O2, O3, N2, CO2)Scattering and absorption by atmospheric particles, micro-dispersed aerosols, thin clouds, and other fine-scale atmospheric phenomena.
Sensitivity and accuracy of refractive index retrievals from measured extinction and absorption cross sections for mobility-selected internally mixed light absorbing aerosols
Published in Aerosol Science and Technology, 2020
Michael I. Cotterell, Kate Szpek, Jim M. Haywood, Justin M. Langridge
Besides being a key microphysical property, aerosol RI is important in atmospheric optics. Provided with additional information on the aerosol shape and size distribution, RI is used to calculate the extensive optical properties that govern aerosol-light interactions. Specifically, the extinction cross section (σext) quantifies the fractional power removed from incident light by a particle and is the sum of the scattering (σsca) and absorption (σabs) cross sections. Quantifying the partitioning of σext into σsca and σabs is crucial in determining whether atmospheric aerosol has a net negative or positive radiative forcing impact (Haywood and Shine 1995). Indeed, the radiative forcing impact for aerosols remains among the largest uncertainties in climate models (Alexander et al. 2013).
Measurements and calculations of H2-broadening and shift parameters of water vapour transitions of the ν1 + ν2 + ν3 band
Published in Molecular Physics, 2018
T. M. Petrova, A. M. Solodov, A. A. Solodov, V. M. Deichuli, V. I. Starikov
The water vapour absorption spectra in 8600–9070 cm−1 region perturbed by H2 pressure were measured using Bruker IFS 125HR high-resolution Fourier transform spectrometer located in V.E. Zuev Institute of Atmospheric Optics SB RAS. The spectrometer was equipped with CaF2 beam splitter, Si detector and tungsten halogen lamp as the light source. The White-type multiple reflection absorption cell with BaF2 windows and with gold-coated mirrors was used for the measurements. The records of the H2O and H2O–H2 absorption spectra were made at room temperature with the optical path length of 1280 cm and unapodised resolution 0.01 cm−1, which corresponds to 90 cm of MOPD in the Bruker definition. The signal-to-noise ratio (expressed as the maximum signal amplitude divided by the RMS noise amplitude) was calculated using the standard procedure of the OPUS 6.5 software. The average value of the RMS noise amplitude in the spectral region under study was 0.0032 giving a signal-to-noise ratio of 3100 for an absorbance of around 1.0. It was obtained by the coaddition of 1200 interferograms. The pressure of the water vapour was 0.0101 and 0.0173 atm and was measured with a Baratron gauge with an estimated uncertainty of 0.25%. The pressure of the H2O–H2 mixture ranged between 0.179 and 0.675 atm and was measured with the manometer DVR-5 (1100 mbar full scale) which has a stated uncertainty of 0.5% according to the manufacturer. All measurements are summarised in Table 1.
Measurements and calculations of H2-broadening and shifting parameters of water vapour transitions in a wide spectral region
Published in Molecular Physics, 2018
Tatiana M. Petrova, Alexander M. Solodov, Alexander A. Solodov, Vladimir M. Deichuli, Vitalii I. Starikov
The absorption spectra of water vapour perturbed by pressurised H2 in the 6700–9000 cm–1 region were measured using Bruker high-resolution Fourier transform spectrometer IFS 125HR located in the V.E. Zuev Institute of Atmospheric Optics SB RAS. The experimental set-up and fitting procedure were described in detail previously in [8,9], and only a brief summary is given here. The spectrometer was equipped with a CaF2 beam splitter, an InSb detector and a tungsten halogen lamp as the light source. The Thermo Electron White type multiple reflection absorption cell with BaF2 windows and with gold-coated mirrors was used for the measurements. The measurements of the H2O and H2O–H2 absorption spectra were made at room temperature with the optical path length of 1280 cm and unapodised resolution 0.01 cm–1, which corresponds to 90 cm of MOPD in the Bruker definition. The signal-to-noise ratio (expressed as the maximum signal amplitude divided by the root-mean square noise amplitude noise amplitude) was calculated using the standard procedure of the OPUS 6.5 software. The average value of the RMS noise amplitude in the spectral region under study was 0.0032 giving a signal-to-noise ratio of 3100 for an absorbance of around 1.0. It was obtained by the co-addition of 1200 interferograms. The water vapour pressure was 0.0101 and 0.0173 atm and was measured with a Baratron gauge with an estimated uncertainty of 0.25%. The pressure of the H2O–H2 mixture ranged between 0.179 and 0.675 atm and was measured with the manometer DVR-5 (1100 mbar full scale) which has a stated uncertainty of 0.5% according to the manufacturer. An empty-cell spectrum recorded before and after filling the gas cell was used as a baseline. All measurements are summarised in Table 1.