The major source of cloud-condensation nuclei (CCN) over the oceans appears to be dimethylsulphide, which is produced by planktonic algae in sea water and oxidizes in the atmosphere to form a sulphate aerosol Because the reflectance (albedo) of clouds (and thus the Earth's radiation budget) is sensitive to CCN density, biological regulation of the climate is possible through the effects of temperature and sunlight on phytoplankton population and dimethylsulphide production. To counteract the warming due to doubling of atmospheric CO2, an approximate doubling of CCN would be needed.

Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate

The JRA-55 Reanalysis: General Specifications and Basic Characteristics

The known optical properties (absorption, scattering, total attenuation, effective attenuation, and/or anisotropy coefficients) of various biological tissues at a variety of wavelengths are reviewed. The theoretical foundations for most experimental approaches are outlined. Relations between Kubelka-Munk parameters and transport coefficients are listed. The optical properties of aorta, liver, and muscle at 633 nm are discussed in detail. An extensive bibliography is provided. >

A review of the optical properties of biological tissues

https://ams.confex.com/ams/pdfpapers/71176.pdf

Fully coupled “online” chemistry within the WRF model

This paper reviews scattering theory required for analysis of light reflected by planetary atmospheres. Section 1 defines the radiative quantities which are observed. Section 2 demonstrates the dependence of single-scattered radiation on the physical properties of the scatterers. Section 3 describes several methods to compute the effects of multiple scattering on the reflected light.

Light scattering in planetary atmospheres

This paper presents a rapid yet accurate method, the “delta-Eddington” approximation, for calculating monochromatic radiative fluxes in an absorbing-scattering atmosphere. By combining a Dirac delta function and a two-term approximation, it overcomes the poor accuracy of the Eddington approximation for highly asymmetric phase functions. The fraction of scattering into the truncated forward peak is taken proportional to the square of the phase function asymmetry factor, which distinguishes the delta-Eddington approximation from others of similar nature. Comparisons of delta-Eddington albedos, transnmissivities and absorptivities with more exact calculations reveal typical differences of 0–0.022 and maximum differences of 0.15 over wide ranges of optical depth, sun angle, surface albedo, single-scattering albedo and phase function asymmetry. Delta-Eddington fluxes are in error, on the average, by no more than 0.5%0, and at the maximum by no more than 2% of the incident flux. This computationally fa...

The delta-Eddington approximation for radiative flux transfer

A high spectral resolution lidar technique to measure optical scattering properties of atmospheric aerosols is described. Light backscattered by the atmosphere from a narrowband optically pumped oscillator-amplifier dye laser is separated into its Doppler broadened molecular and elastically scattered aerosol components by a two-channel Fabry-Perot polyetalon interferometer. Aerosol optical properties, such as the backscatter ratio, optical depth, extinction cross section, scattering cross section, and the backscatter phase function, are derived from the two-channel measurements.

High spectral resolution lidar to measure optical scattering properties of atmospheric aerosols. 1: Theory and instrumentation

Eddington's approximation was employed to compute the irradiances passing through atmospheres consisting of several different, albeit internally homogeneous, layers, as a function of solar zenith angle, albedo for single scatering, the asymmetry factor of the phase function, and the albedo of the underlying surface. Results computed for a single layer atmosphere were found to agree with more exact computations within a few percent. Irradiances within several vertically inhomogeneous three-layer model atmospheres were computed. Effects caused by the vertically inhomogeneous structure are considered. It is noted, for example, that the irradiance within an atmosphere can be greater than that incident upon the atmosphere bemuse radiation may he partially trapped within the atmosphere. The Eddington approximation affords a means to rapidly compute irradiances within realistic inhomogeneous atmospheres with an accuracy of several percent.

The Transfer of Solar Irradiance Through Inhomogeneous Turbid Atmospheres Evaluated by Eddington's Approximation

A numerical algorithm based on Eddington's second approximation to the equation of radiative transfer has been developed in order to compute the radiances with horizontal and vertical polarization that emerge from precipitating clouds. This algorithm yields a rapid solution to problems pertaining to clouds with vertically inhomogeneous structure. Precipitating clouds containing liquid, mixtures of phases, and ice hydrometeors are modelled. It is shown that the lower-frequency radiances are sensitive to liquid precipitation at low altitudes while the higher-frequency radiances are more sensitive to the ice hydrometeors at the cloud tops. The extinction coefficients of aspherical hydrometeors are presented as a function of rainfall rates. The fact that vertically polarized radiances are warmer than horizontally polarized ones at high rainfall rates, with the difference diminishing at lower frequencies, is due to aspherical ice hydrometeors in the upper regions of precipitating clouds.

Microwave radiances from precipitating clouds containing aspherical ice, combined phase, and liquid hydrometeors

Monte Carlo techniques are utilized to compute monostatic lidar returns from turbid atmospheres. Examples are evaluated for thick hazes, clouds, fogs and rain. The effects of multiple scattering are significant in the cases considered. Results are compared with those obtained by Eloranta (1972) to describe doubly scattered lidar returns and the agreement is satisfactory, provided that higher orders of multiple scattering are negligible.

J. A. Weinman

Papers

The delta-Eddington approximation for radiative flux transfer

High spectral resolution lidar to measure optical scattering properties of atmospheric aerosols. 1: Theory and instrumentation

The Transfer of Solar Irradiance Through Inhomogeneous Turbid Atmospheres Evaluated by Eddington's Approximation

Microwave radiances from precipitating clouds containing aspherical ice, combined phase, and liquid hydrometeors

Monte Carlo Analysis of Multiply Scattered Lidar Returns.