Water vapor near Venus cloud tops from VIRTIS-H/Venus express observations 2006–2011

Cottini, V.; Ignatiev, N.; Piccioni, G.; Drossart, P.

doi:10.1016/j.pss.2015.03.012

Cited by 49 publications

(35 citation statements)

References 21 publications

(43 reference statements)

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“…The steadystate water vapor mixing ratio about the photochemical production altitude is around 18 ppmv, noticeably smaller than the 22 ppmv observed in the nominal case. Even still, this is a significantly larger value than would be expected from the Cottini et al (2015) observations, Fig. 15 Contour plot of particle size distributions for the nominal photochemistry simulation, as functions of radius and altitude, for each simulated latitude profile but somewhat more consistent with the observations by Fedorova et al (2016).…”

Section: Enhanced Photochemical Production Ratessupporting

confidence: 59%

“…The water vapor profile also resembles the condensational cloud case, except there is more variation with latitude at altitudes above 60 km. Note that these values of water vapor mixing ratio are all significantly larger than the 2 ± 2 ppmv of water vapor reported by Cottini et al (2015) above the cloud tops (while the derived cloud top altitude varied with latitude over a range from about 64 km to about 71 km). However, these simulated values of water vapor mixing ratio are consistent with the analysis of SPICAV-UV data done by Fedorova et al (2016), who found water vapor mixing ratios varying between 4 and 11 ppmv near the equator, measured at a sampling altitude a few kilometers deeper than that sensed by VIRTIS.…”

Section: Nominal Modelmentioning

confidence: 55%

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Effects of variation in coagulation and photochemistry parameters on the particle size distributions in the Venus clouds

McGouldrick

2017

Earth Planets Space

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This paper explores the effects that variation in the coalescence efficiency of the Venus cloud particles can have on the structure of the Venus cloud. It is motivated by the acknowledgment of uncertainties in the measured parameters-and the assumptions made to account for them-that define our present knowledge of the particle characteristics. Specifically, we explore the consequence of allowing the coalescence efficiency of supercooled sulfuric acid in the upper clouds to tend to zero. This produces a cloud that occasionally exhibits an enhancement of small particles at altitude (similar to the upper hazes observed by Pioneer Venus and subsequently shown to be somewhat transient). This simulated cloud occasionally exhibits a rapid growth of particle size near cloud base, exhibiting characteristics similar to those seen in the controversial Mode 3 particles. These results demonstrate that a subset of the variations observed as near-infrared opacity variations in the lower and middle clouds of Venus can be explained by microphysical, in addition to dynamical, variations. Furthermore, the existence of a population of particles exhibiting less efficient coalescence efficiencies would support the likelihood of conditions suitable for charge exchange, hence lightning, in the Venus clouds. We recommend future laboratory studies on the coalescence properties of sulfuric acid under the range of conditions experienced in the Venus clouds. We also recommend future in situ measurements to better characterize the properties of the cloud particles themselves, especially composition and particle habits (shapes).

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Section: Enhanced Photochemical Production Ratessupporting

confidence: 59%

Section: Nominal Modelmentioning

confidence: 55%

Effects of variation in coagulation and photochemistry parameters on the particle size distributions in the Venus clouds

McGouldrick

2017

Earth Planets Space

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“…We note that the vertical structure of the upper clouds may affect the solar heating rate (Lee et al 2015b), but the structure of the upper clouds at low latitudes from near infrared observations is shown to be rather stable during the time of Venus Express (Ignatiev et al 2009;Cottini et al 2015;Fedorova et al 2016), validating the use of a fixed cloud structure. Other analyses suggest that the vertical distribution of the unknown absorber may sometimes extend vertically above the cloud top level (Molaverdikhani et al 2012;Lee et al 2015a).…”

Section: Solar Heating Variationsmentioning

confidence: 67%

Long-term Variations of Venus’s 365 nm Albedo Observed by Venus Express, Akatsuki, MESSENGER, and the Hubble Space Telescope

Lee

Jessup

Pérez‐Hoyos

et al. 2019

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An unknown absorber near the cloud top level of Venus generates a broad absorption feature from the ultraviolet (UV) to visible, peaking around 360 nm, and therefore plays a critical role in the solar energy absorption. We present a quantitative study on the variability of the cloud albedo at 365 nm and its impact on Venus solar heating rates based on an analysis of Venus Express and Akatsuki's UV images, and Hubble Space Telescope and MESSENGER's UV spectral data; in this analysis the calibration correction factor of the UV images of Venus Express (VMC) is updated relative to the Hubble and MESSENGER albedo measurements. Our results indicate that the 365-nm albedo varied by a factor of 2 from 2006 to 2017 over the entire planet, producing a 25-40% change in the low latitude solar heating rate according to our radiative transfer calculations. Thus, the cloud top level atmosphere should have experienced considerable solar heating variations over this period. Our global circulation model calculations show that this variable solar heating rate may explain the observed variations of zonal wind from 2006 to 2017. Overlaps in the timescale of the long-term UV albedo and the solar activity variations make it plausible that solar extreme UV intensity and cosmic-ray variations influenced the observed albedo trends. The albedo variations might also be linked with temporal variations of the upper cloud SO 2 gas abundance, which affects the H 2 SO 4 -H 2 O aerosol formation.

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“…6 (for SO 2 measurements, see also Fig. 5: q(SO 2 ) ∼ 0.01 to 0.2 ppmv; from Cottini et al (2015) and references contained therein, f (H 2 O) ∼ 2 to 7 ppmv using combined lower and upper latitude values). Using the observed values in a simple comparison with the modelled results, we can predict the range of values of q(SO 2 ) with corresponding q(H 2 O) values (or conversely) at 58 km for any colour contour in the valid bracketed region.…”

Section: So 2 and H 2 O Regulation Via Formation Of H 2 So 4 Krasnopomentioning

confidence: 98%

“…They obtained values between 2 and 10 ppmv near the cloud top (65-74 km). Water vapour abundances near the cloud tops (at 69.5 ± 2 km) were also obtained with VIRTIS-H on the day side (Cottini et al 2012(Cottini et al , 2015) (see Sect. 3.2) and by ground-based spectroscopy at 74 km (Krasnopolsky et al 2013).…”

Section: H 2 O and Hdomentioning

confidence: 99%

Composition and Chemistry of the Neutral Atmosphere of Venus

Marcq¹,

Mills²,

Sandor³

et al. 2017

Space Sci Rev

100

117

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International audienceThis paper deals with the composition and chemical processes occurring in the neutral atmosphere of Venus. Since the last synthesis, observers as well as modellers have emphasised the spatial and temporal variability of minor species, going beyond a static and uniform picture that may have prevailed in the past. The outline of this paper acknowledges this situation and follows closely the different dimensions along which variability in composition can be observed: vertical, latitudinal, longitudinal, temporal. The strong differences between the atmosphere below and above the cloud layers also dictate the structure of this paper. Observational constraints, obtained from both Earth and Venus Express, as well as 1D, 2D and 3D models results obtained since 1997 are also extensively referred and commented by the authors. An non-exhaustive list of topics included follows: modelled and observed latitudinal and vertical profiles of CO and OCS below the clouds of Venus; vertical profiles of CO and SO2 above the clouds as observed by solar occultation and modelled; temporal and spatial variability of sulphur oxides above the clouds. As a conclusion, open questions and topics of interest for further studies are discussed

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Water vapor near Venus cloud tops from VIRTIS-H/Venus express observations 2006–2011

Cited by 49 publications

References 21 publications

Effects of variation in coagulation and photochemistry parameters on the particle size distributions in the Venus clouds

Effects of variation in coagulation and photochemistry parameters on the particle size distributions in the Venus clouds

Long-term Variations of Venus’s 365 nm Albedo Observed by Venus Express, Akatsuki, MESSENGER, and the Hubble Space Telescope

Composition and Chemistry of the Neutral Atmosphere of Venus

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