From the contents: Preface.- 1. Description of Polarized Light.- 2. Single Scattering.- 3. Plane-parallel Media.- 4. Orders of Scattering and Multiple-Scattering Matrices.- 5. The Adding-doubling Method.- A. Mueller Calculus.- B. Generalized Spherical Functions.- C. Expanding the Elements of F (T).- D. Size Distributions.- E. Proofs of Relationships for Multiple-Scattering Matrices.- F. Supermatrices and Extended Supermatrices.- Bibliography.- Index.

Transfer of Polarized Light in Planetary Atmospheres: Basic Concepts And Practical Methods

[1] Simultaneous observations of Venus by Visible and Infrared Thermal Imaging Spectrometer and Venus Monitoring Camera onboard the Venus Express spacecraft are used to map the cloud top altitude and to relate it to the ultraviolet (UV) markings. The cloud top altitude is retrieved from the depth of CO2 absorption band at 1.6 μm. In low and middle latitudes the cloud top is located at 74 ± 1 km. It decreases poleward of ±50° and reaches 63–69 km in the polar regions. This depression coincides with the eye of the planetary vortex. At the same latitude and hour angle, cloud top can experience fast variations of about 1 km in tens of hours, while larger long-term variations of several kilometers have been observed only at high latitudes. UV markings correlate with the cloud altimetry, however, the difference between adjacent UV dark and bright regions does not exceed several hundred meters. Surprisingly, CO2 absorption bands are often weaker in the dark UV features, indicating that these clouds may be a few hundred meters higher or have a larger scale height than neighboring clouds. Ultraviolet dark spiral arms, which are often seen at about −70°, correspond to higher altitudes or to the regions with strong latitudinal gradient of the cloud top altitude. Cloud altimetry in the polar region reveals the structure that correlates with the thermal emission maps but is invisible in UV images. This implies that the UV optically thick polar hood is transparent in the near IR.

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Altimetry of the Venus cloud tops from the Venus Express observations

More than three decades have passed since the publication of the last review of the Venus clouds and hazes. The paper published in 1983 in the Venus book summarized the discoveries and findings of the US Pioneer Venus and a series of Soviet Venera spacecraft (Esposito et al. in Venus, p. 484, 1983). Due to the emphasis on in-situ investigations from descent probes, those missions established the basic features of the Venus cloud system, its vertical structure, composition and microphysical properties. Since then, significant progress in understanding of the Venus clouds has been achieved due to exploitation of new observation techniques onboard Galileo and Messenger flyby spacecraft and Venus Express and Akatsuki orbiters. They included detailed investigation of the mesospheric hazes in solar and stellar occultation geometry applied in the broad spectral range from UV to thermal IR. Imaging spectroscopy in the near-IR transparency “windows” on the night side opened a new and very effective way of sounding the deep atmosphere. This technique together with near-simultaneous UV imaging enabled comprehensive study of the cloud morphology from the cloud top to its deep layers. Venus Express operated from April 2006 until December 2014 and provided a continuous data set characterizing Venus clouds and hazes over a time span of almost 14 Venus years thus enabling a detailed study of temporal and spatial variability. The polar orbit of Venus Express allowed complete latitudinal coverage. These studies are being complemented by JAXA Akatsuki orbiter that began observations in May 2016. This paper reviews the current status of our knowledge of the Venus cloud system focusing mainly on the results acquired after the Venera, Pioneer Venus and Vega missions.

/pdf/clouds-and-hazes-of-venus-28mrkf29jc.pdf

Clouds and Hazes of Venus

Venus’ atmosphere has a rich chemistry involving interactions among sulfur,
chlorine, nitrogen, hydrogen, and oxygen radicals. The chemical regimes in the
atmosphere range from ion-neutral reactions in the ionosphere to photochemistry
in the middle atmosphere to thermal equilibrium chemistry and surface-atmosphere
reactions in the lower atmosphere. This variety makes Venus an important planet
to understand within the context of terrestrial-like planets, both in our own solar
system and outside it. The primary chemical cycles are believed known but surprisingly
few details about these cycles have been fully verified by concurrence
among observations, experiments, and modeling. Good models have been developed
that account for many properties of the cloud layers, but the size distribution,
shape, and composition of the majority of the aerosol mass are still open issues.
This chapter reviews the state of knowledge prior to the Venus Express mission
for the composition, chemistry, and clouds of the neutral atmosphere on Venus.
Observations by instruments on Venus Express, in combination with ground-based
observations, laboratory experiments, and numerical modeling, should answer some
of the major open questions regarding the composition, chemistry, and clouds of
Venus’ atmosphere.

/pdf/atmospheric-composition-chemistry-and-clouds-11bj7noqry.pdf

Atmospheric Composition, Chemistry, and Clouds

http://web.uvic.ca/~rhyndman/PublicationPDFs/RyuetalUlleungBasinHydrate2009.pdf

Gas hydrates in the western deep-water Ulleung Basin, East Sea of Korea

[1] The spatial and temporal variations of the polarization of light scattered by Venus, as observed by the Pioneer Venus Orbiter between 1978 and 1990, is analyzed in terms of spatial and temporal variations of Venus upper haze properties. Special attention is given to choosing maps with sufficiently accurate geometrical information. This selection involves multiple-scattering calculations for a number of reasonable models for the Venus atmosphere. For a set of observations in four wavelength bands of the Venus disk as a whole or a particular region thereof, observed values of Stokes parameters I and Q were used to obtain the average observed relative Stokes parameter qobs. Subsequently, the haze particle column density and the cloud top pressure were iteratively adjusted until values of qobs at two wavelengths were reproduced. For the planet as a whole, it was found that the haze particle column density decreased gradually during the Pioneer Venus Orbiter mission, whereas little significant temporal variability was found for the cloud top pressure. Similar long-term behavior was derived for selected regions of Venus. Regions at higher latitudes exhibited higher values of both the haze particle column density and the cloud top pressure than regions at lower latitudes. Something similar holds for regions with low solar elevations as compared to regions in which the Sun was close to the zenith.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2001JE001502

C. J. Braak

Papers

Spatial and temporal variations of Venus haze properties obtained from Pioneer Venus Orbiter polarimetry