Top PDF Aerosols and Chemistry in the Planetary Atmospheres

Aerosols and Chemistry in the Planetary Atmospheres

Aerosols and Chemistry in the Planetary Atmospheres

On the other hand, the nonlinear feedbacks in the complicated photochemical-advective- diffusive system may blur the physical insights. A simple but realistic analytical solution can be considered as a benchmark case in understanding the basic behavior of the system, although only to some extent. Previous studies did not focus much on the analytical benchmark cases in the atmospheric tracer transport. In civil engineering, the regional Gaussian-plume dispersion models have been studies for many years, and the analytical solutions for the three-dimensional (3-D) diffusion equation could be obtained, although they may not be in the explicit forms (e.g., Lin and Hildemann, 1997). But those solutions are not useful for this study because (1) they are too complicated to show any physical insight; (2) they are restricted to a nonreactive contaminant; and (3) they are not in the planetary scale in which the sphericity of the planet should be taken into account. For the simple planetary-scale analytical solutions, besides Shia et al. (1990), previous attempts mainly focused on the 1-D solutions. Neglecting the chemistry, Chamberlain and Hunten (1987) derived the 1-D analytical solution with an exponential form of eddy and molecular diffusivities. Yelle et al. (2001) reported a 1-D diffusive equilibrium CH 4 profile, which is
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AerChemMIP: Quantifying the effects of chemistry and aerosols in CMIP6

AerChemMIP: Quantifying the effects of chemistry and aerosols in CMIP6

The contribution of tropospheric ozone precursors to radia- tive forcing (through changes in ozone and methane) has been considered in successive IPCC assessments since IPCC (1994) and the Second Assessment Report (IPCC, 1996), where a combination of 2-D and 3-D chemistry models was used (PhotoComp in Olson et al., 1997). A more rigorous in- tercomparison of 3-D chemistry transport models (OxComp in Prather et al., 2001; Gauss et al., 2003) provided informa- tion on the geographical distribution of ozone forcing for the IPCC Third Assessment Report (Ramaswamy et al., 2001). The IPCC Fourth Assessment report (AR4) (Forster et al., 2007) again used a multi-model framework (Atmospheric Composition Change European Network – ACCENT) to cal- culate maps of ozone radiative forcing (Gauss et al., 2006). Here the models were still nearly all offline chemistry trans- port models, and none of the climate models used in AR4 (those participating in the CMIP3 project) included tropo- spheric ozone chemistry. The radiative forcing of ozone in all cases was calculated using offline radiative transfer models, usually for “pre-industrial”, “present” and one or two future time slices. It was not until the CMIP5 project that a few of the climate models included interactive tropospheric chem- istry. The aim of ACCMIP (Lamarque et al., 2013) was to quantify the contribution of ozone and aerosols to the radia- tive forcing in the CMIP5 models that included these com- ponents. In practice, the model setups for CMIP5 and AC- CMIP were usually different (the ACCMIP models tended to have lower resolution but include greater complexity in chemistry and aerosols) so that ACCMIP was not able to fully characterise the forcings of most simulations submitted
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Simulating the Impacts of Marine Organic Emissions on Global Atmospheric Chemistry and Aerosols Using an Online Coupled Meteorology and Chemistry Model

Simulating the Impacts of Marine Organic Emissions on Global Atmospheric Chemistry and Aerosols Using an Online Coupled Meteorology and Chemistry Model

In this study, we use the online-coupled global-through-urban weather and forecasting model with chemistry (GU-WRF/Chem) to quantify the impact of online emissions of marine isoprene and POA on atmospheric che- mistry and aerosol abundance in remote marine and coastal regions. GU-WRF/Chem is capable of simulating these impacts across a wide range of spatial scales while reducing uncertainties from the use of offline-coupled model systems with inconsistent model treatments [22]. Comprehensive treatments of gas-phase chemistry and aerosol microphysics, in conjunction with online emissions of marine BVOC and POA, are expected to improve model predictions of surface concentrations of BVOCs, O 3 , and organic aerosols. The overall objective of this
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Lidar signal simulation for the evaluation of aerosols in chemistry transport models

Lidar signal simulation for the evaluation of aerosols in chemistry transport models

The complementary active remote-sensing observations of the Cloud-Aerosol Lidar with Orthogonal Polarisation (CALIOP) lidar in space (on board CALIPSO, also part of the A-Train) provide valuable information on the vertical dis- tribution of aerosols (Winker et al., 2009). They were used in several recent studies for the evaluation of chemistry trans- port model (CTM) simulations (e.g. Yu et al., 2010; Ford and Heald, 2012; Ridley et al., 2012). The classic approach for comparing model simulations and satellite observations is using the level 2 (L2) retrievals, which are derived from the Level 1 (L1) observations. The reliability of L2 retrievals is constantly improving (V3 data products have considerably improved compared to the V2 release), and these data have proven to be very useful for analysing aerosol-related pollu- tion events. However, it is a well-documented fact that they are prone to uncertainties (Liu et al., 2009; Omar et al., 2010; Young and Vaughan, 2009; Winker et al., 2009). More specif- ically, the accuracy of these products depends to a large ex- tent on the uncertainties of each step (algorithm) in the pro- cessing chain. A key parameter that is used to derive L2 prod- ucts (backscatter and extinction coefficients) from attenuated backscatter profiles (L1 data) is the extinction-to-backscatter ratio (lidar ratio). The mean values used are based on pre- scribed bi-modal size distributions and characteristic com-
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Interactions between Tropospheric Chemistry and Aerosols in a Unified GCM Simulation

Interactions between Tropospheric Chemistry and Aerosols in a Unified GCM Simulation

thesis 20110310 0002 Interactions between Tropospheric Chemistry and Aerosols in a Unified GCM Simulation Thesis by Hong Liao In Partial Fulfillment of the Requirements for the Degree of Doctor of Phi[.]

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Description and evaluation of tropospheric chemistry and aerosols in the Community Earth System Model (CESM1.2)

Description and evaluation of tropospheric chemistry and aerosols in the Community Earth System Model (CESM1.2)

The Community Earth System Model (CESM) is a com- prehensive model that couples different independent mod- els for atmosphere, land, ocean, sea ice, land ice, and river runoff (e.g., Neale et al., 2013; Lamarque et al., 2012). It can be used in various configurations, depending on the use of different components and the coupling between them. The atmospheric component of CESM, the Community Atmo- sphere Model (CAM), has the capability of including chem- istry of varying complexity. Default CESM configurations used for long-term climate model simulations usually include prescribed chemical fields in the atmosphere using monthly averages. To produce those prescribed input fields, simula- tions with a detailed representation of chemistry and aerosol processes are required. Furthermore, nonlinear interactions between chemistry and aerosols in the atmosphere are impor- tant for chemistry–climate interactions (e.g., Lamarque et al., 2005; Isaksen et al., 2009) or for the simulation of air quality. In CESM version 1.2, CAM version 5 (CAM5), exten- sive tropospheric and stratospheric chemistry, referred here- after to as CAM5-chem, has been successfully implemented. The performance of CAM version 4 (CAM4) with interac- tive chemistry, referred to as CAM4-chem, has been dis- cussed in Lamarque et al. (2012). In this study, a similar setup of both CAM4-chem and CAM5-chem allows for the comparison of both versions and their performance in com- parison to observations. The two atmospheric configurations CAM4-chem and CAM5-chem differ in various aspects, in- cluding the treatment of cloud, convection, turbulent mixing, and aerosol processes (e.g., Neale et al., 2013; Gent et al., 2011; Kay et al., 2012; Liu et al., 2012), whereas the gas- phase chemistry is identical. Resulting differences in dynam- ics, clouds, precipitation, and radiation will alter chemical re- actions in the gas, aqueous, and aerosol phases, and removal processes, and therefore the chemical composition of the at- mosphere in these configurations.
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Description and evaluation of tropospheric chemistry and aerosols in the Community Earth System Model (CESM1.2)

Description and evaluation of tropospheric chemistry and aerosols in the Community Earth System Model (CESM1.2)

The Community Earth System Model (CESM) is a com- prehensive model that couples different independent mod- els for atmosphere, land, ocean, sea ice, land ice, and river runoff (e.g., Neale et al., 2013; Lamarque et al., 2012). It can be used in various configurations, depending on the use of different components and the coupling between them. The atmospheric component of CESM, the Community Atmo- sphere Model (CAM), has the capability of including chem- istry of varying complexity. Default CESM configurations used for long-term climate model simulations usually include prescribed chemical fields in the atmosphere using monthly averages. To produce those prescribed input fields, simula- tions with a detailed representation of chemistry and aerosol processes are required. Furthermore, nonlinear interactions between chemistry and aerosols in the atmosphere are impor- tant for chemistry–climate interactions (e.g., Lamarque et al., 2005; Isaksen et al., 2009) or for the simulation of air quality. In CESM version 1.2, CAM version 5 (CAM5), exten- sive tropospheric and stratospheric chemistry, referred here- after to as CAM5-chem, has been successfully implemented. The performance of CAM version 4 (CAM4) with interac- tive chemistry, referred to as CAM4-chem, has been dis- cussed in Lamarque et al. (2012). In this study, a similar setup of both CAM4-chem and CAM5-chem allows for the comparison of both versions and their performance in com- parison to observations. The two atmospheric configurations CAM4-chem and CAM5-chem differ in various aspects, in- cluding the treatment of cloud, convection, turbulent mixing, and aerosol processes (e.g., Neale et al., 2013; Gent et al., 2011; Kay et al., 2012; Liu et al., 2012), whereas the gas- phase chemistry is identical. Resulting differences in dynam- ics, clouds, precipitation, and radiation will alter chemical re- actions in the gas, aqueous, and aerosol phases, and removal processes, and therefore the chemical composition of the at- mosphere in these configurations.
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Simulation of tropospheric chemistry and aerosols with the climate model EC-Earth

Simulation of tropospheric chemistry and aerosols with the climate model EC-Earth

Abstract. We have integrated the atmospheric chemistry and transport model TM5 into the global climate model EC-Earth version 2.4. We present an overview of the TM5 model and the two-way data exchange between TM5 and the IFS model from the European Centre for Medium-Range Weather Forecasts (ECMWF), the atmospheric general cir- culation model of EC-Earth. In this paper we evaluate the simulation of tropospheric chemistry and aerosols in a one- way coupled configuration. We have carried out a decadal simulation for present-day conditions and calculated chem- ical budgets and climatologies of tracer concentrations and aerosol optical depth. For comparison we have also per- formed offline simulations driven by meteorological fields from ECMWF’s ERA-Interim reanalysis and output from the EC-Earth model itself. Compared to the offline simula- tions, the online-coupled system produces more efficient ver- tical mixing in the troposphere, which reflects an improve- ment of the treatment of cumulus convection. The chem- istry in the EC-Earth simulations is affected by the fact that the current version of EC-Earth produces a cold bias with too dry air in large parts of the troposphere. Compared to the ERA-Interim driven simulation, the oxidizing capacity in EC-Earth is lower in the tropics and higher in the extrat- ropics. The atmospheric lifetime of methane in EC-Earth is 9.4 years, which is 7 % longer than the lifetime obtained with ERA-Interim but remains well within the range reported in the literature. We further evaluate the model by comparing the simulated climatologies of surface radon-222 and carbon
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Description and evaluation of tropospheric chemistry and aerosols in the Community Earth System Model (CESM1.2)

Description and evaluation of tropospheric chemistry and aerosols in the Community Earth System Model (CESM1.2)

Abstract. The Community Atmosphere Model (CAM), ver- sion 5, is now coupled to extensive tropospheric and strato- spheric chemistry, called CAM5-chem, and is available in addition to CAM4-chem in the Community Earth System Model (CESM) version 1.2. The main focus of this paper is to compare the performance of configurations with internally derived “free running” (FR) meteorology and “specified dy- namics” (SD) against observations from surface, aircraft, and satellite, as well as understand the origin of the identified differences. We focus on the representation of aerosols and chemistry. All model configurations reproduce tropospheric ozone for most regions based on in situ and satellite ob- servations. However, shortcomings exist in the representa- tion of ozone precursors and aerosols. Tropospheric ozone in all model configurations agrees for the most part with ozonesondes and satellite observations in the tropics and the Northern Hemisphere within the variability of the observa- tions. Southern hemispheric tropospheric ozone is consis- tently underestimated by up to 25 %. Differences in con- vection and stratosphere to troposphere exchange processes are mostly responsible for differences in ozone in the differ- ent model configurations. Carbon monoxide (CO) and other volatile organic compounds are largely underestimated in Northern Hemisphere mid-latitudes based on satellite and aircraft observations. Nitrogen oxides (NO x ) are biased low
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First implementation of secondary inorganic aerosols in the MOCAGE version R2.15.0 chemistry transport model

First implementation of secondary inorganic aerosols in the MOCAGE version R2.15.0 chemistry transport model

In the implementation, we made choices for representing phenomena favouring computational efficiency over a very detailed representation while keeping a good accuracy. There are weaknesses in this SIA module which could be improved. Firstly, all the microphysical processes have been treated im- plicitly in a very simple way. A next step would be to include them using physical parameterizations, in particular, nucle- ation, condensation and coagulation, which are very impor- tant for the time evolution of the aerosol sizes. Another as- pect to work on is the thermodynamic equilibrium hypoth- esis which leads to uncertainties. To improve this, it is nec- essary to account for the kinetics of the transfer between the gas phase and the aerosol phase, especially for big particles (Wexler and Seinfeld, 1990; Capaldo et al., 2000). A third improvement would be to take into account the formation of secondary organic aerosols in order to have the complete range of atmospheric particles and be able to represent prop- erly the different interactions and impact of aerosols. One of the final goals is to integrate this module for operational fore- casts into the Prev’Air and COPERNICUS programs. The MOCAGE model will also be used to make research studies including long run simulations, for instance, for the CCMI programme (Chemistry–Climate Model initiative) and the analysis of the aerosol budget in the Mediterranean area.
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Towards an online-coupled chemistry-climate model: evaluation of trace gases and aerosols in COSMO-ART

Towards an online-coupled chemistry-climate model: evaluation of trace gases and aerosols in COSMO-ART

COSMO-ART is a regional chemistry transport model, online-coupled to the COSMO regional numerical weather prediction and climate model (Baldauf et al., 2011). COSMO is operationally used for numerical weather prediction (NWP) purposes by several European national meteorolog- ical services and research institutes. In its climate version (Rockel et al., 2008) it has been used in several studies of regional climate impact assessment (e.g. Jaeger and Senevi- ratne, 2010; Suklitsch et al., 2008; Hohenegger et al., 2008) and participated in the IPCC fourth assessment report mod- eling ensemble (Christensen et al., 2007). The extension for Aerosols and Reactive Trace gases (ART) contains a mod- ified version of the Regional Acid Deposition Model, Ver- sion 2 (RADM2) gas-phase chemistry mechanism (Stock- well et al., 1990). It has been extended by a more sophis- ticated isoprene scheme of Geiger et al. (2003) for a better description of biogenic volatile organic compounds (VOC), but does not include recent findings regarding formation of secondary organic aerosols and OH recycling due to isoprene chemistry (e.g. Paulot et al., 2009). Aerosols are represented by the modal aerosol module MADE (Modal Aerosol Dy- namics Model for Europe, Ackermann et al., 1998), im- proved by explicit treatment of soot aging through conden- sation of inorganic salts (Riemer et al., 2003) and additional modes for mineral dust (Stanelle et al., 2010) and sea salt. Nucleation of new particles is formulated according to Ker- minen and Wexler (1994) allowing for binary homogeneous nucleation of sulfuric acid. The condensation of vapours from biogenic and anthropogenic VOCs is parametrized with the Secondary Organic Aerosol Model (SORGAM) of Schell et al. (2001). This is still a commonly used module, although Fast et al. (2009) showed that this scheme underpredicts SOA concentrations by up to a factor of 10 in very polluted regions. Biogenic VOC emission fluxes, considering iso- prene, α-pinene, other monoterpenes and a class of uniden- tified compounds, are calculated online with a Guenther- type model presented in Vogel et al. (1995), using land use data from the Global Land Cover 2000 (GLC2000) dataset (Bartholom´e and Belward, 2005). Seasalt emissions follow Lundgren (2006), and mineral dust is parameterized as de- scribed in Vogel et al. (2006). Dry deposition is modeled by a resistance approach (Baer and Nester, 1992). Washout of aerosols is included by a parameterization of Rinke (2008). Wet removal of gases and aqueous-phase chemistry are cur- rently not considered. COSMO-ART is fully online-coupled, and currently allows for feedbacks of aerosols on radiation (direct/semi-indirect effects). Cloud feedbacks (indirect ef- fects) have been included in a research version (Bangert et al., 2011) but were not used in this work. A complete de- scription of the modeling system can be found in Vogel et al.
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Temporal and spatial variation in major ion chemistry and source identification of secondary inorganic aerosols in Northern Zhejiang Province, China

Temporal and spatial variation in major ion chemistry and source identification of secondary inorganic aerosols in Northern Zhejiang Province, China

Literature data of averaged PM2.5, WSII, SO42-, NO3- and NH4+ concentrations in North China Plain NCP, Northwest China NWC, Pearl River Delta PRD.. and Yangtze River Delta YRD of China M[r]

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Modelling multiphase chemistry in deliquescent aerosols and clouds using CAPRAM3.0i

Modelling multiphase chemistry in deliquescent aerosols and clouds using CAPRAM3.0i

The adiabatic air parcel model SPACCIM combines a complex size-resolved multiphase chem- istry model and a model with a description of cloud microphysics. The SPACCIM model treats the aqueous phase chemistry in both deliquesced particles and cloud droplets, which can alter the chemical aerosol composition throughout the simulation time. The microphysical model applied in SPACCIM model framework is mainly based on Simmel and Wurzler (2006) and Simmel et al. (2005). The cloud droplet formation, evolution and evaporation are implemented using a one- dimensional sectional microphysics considering deliquesced particles and droplets, respectively. All microphysical parameters required by the multiphase chemistry model are transferred from the microphysical model after a coupling time step of 10 s model-time. In the present model studies, a moving bin version of SPACCIM was used. In the model, the growth and shrinking of aerosol particles by water vapour diffusion as well as nucleation and growth/evaporation of cloud droplets is considered. The dynamic growth rate in the condensation/evaporation process as well as the droplet activation is based on Köhler theory. Because of the focus of the present model studies on the complex multiphase chemistry, other microphysical processes such as impaction of aerosol particles and collision/coalescence of droplets and thus precipitation have not been taken into account. Furthermore, it should be noted that such an air parcel model is not able to assess the complexity of tropospheric mixing processes. The complex model framework enables detailed investigations of the multiphase chemical processing of gases, deliquescent particles and cloud droplets. Further details about the SPACCIM model are given elsewhere in the literature (see Wolke et al. 2005; Sehili et al. 2005; Tilgner and Herrmann 2010 and references therein). 2.2 Non-permanent cloud simulations with SPACCIM
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Convection in Planetary Atmospheres: Titan's Haze, Saturn's Storm and Jupiter's Water

Convection in Planetary Atmospheres: Titan's Haze, Saturn's Storm and Jupiter's Water

particle density increases, they absorb enough solar heat to create a local temperature inversion. Liang et al. (2007) estimated a heating rate of aerosols which results in a temperature inversion of about 20 K. The temperature inversion layer stabilizes the atmosphere, creating a low eddy diffusion zone under it, and slows the downward transport of aerosols. The aerosols are retained in this layer and particles could grow more rapidly through fractal aggregation , absorbing more heat as a result. This kind of positive feedback mechanism predicts that the vertical mixing intensity would decrease in the inversion layer (at about 500 km), which is manifested by a decrease in the eddy diffusivity. This growth of fractal aerosol permitted by a slow vertical transport in a stable layer might explain the existence of the detached haze layer observed by Cassini/UVIS. A rigorous study of such a mechanism requires a coupled modeling of radiative processes, aerosol microphysics, chemical kinetics and dynamics, which is deferred to later work.
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Analyses of Planetary Atmospheres Across the Spectrum: From Titan to Exoplanets

Analyses of Planetary Atmospheres Across the Spectrum: From Titan to Exoplanets

Secondary eclipse observations of gas giant planets provide an invaluable tool for probing the temper- ature and compositional state of their atmospheres by detecting light emitted from the planet itself. Studies utilizing Spitzer have previously observed secondary eclipses of more than fifty transiting planets (Madhusudhan et al., 2014), but the vast majority of these objects have been Jovian-mass planets with temperatures between 1500-2500 K. The atmospheres of smaller and cooler planets remain mostly uncharted territory, in part because it is extremely challenging to detect their ther- mal emission at the near-infrared wavelengths accessible to most telescopes. Equilibrium chemistry models predict that at around 1000 K the dominant reservoir of atmospheric carbon shifts from CO and CO 2 to CH 4 , a phenomenon similar to that which occurs in the atmospheres of cool, low-mass
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Clouds and Hazes in Planetary Atmospheres

Clouds and Hazes in Planetary Atmospheres

Photochemical hazes naturally arise in reducing atmospheres due to the destruction of methane and higher hydrocarbons by solar UV photons and high-energy ions and neutrals, followed by polymerization of the resulting radical species. Such condi- tions have been hypothesized to exist in the atmosphere of Pluto from detections of spectral features belonging to methane gas / ice (e.g. Cruikshank and Brown, 1986; Owen et al., 1993), which suggests the possible existence of hazes therein. How- ever, previous attempts at characterizing the lower atmosphere of Pluto by exploit- ing the “knee” in stellar occultation light curves (where the slope of ingress / egress steepens closer to Pluto’s surface) have been inconclusive, as both a strong thermal inversion and a haze layer can produce such an observation (e.g. Elliot, Dunham, et al., 1989; Stansberry, Lunine, Hubbard, et al., 1994; Young et al., 2008; Person et al., 2013; Olkin et al., 2014; Dias-Oliveira et al., 2015; Gulbis et al., 2015). The July 14th, 2015 flyby of Pluto by the New Horizons probe settled the debate by confirming the existence of optically thin haze layers pervading the lower few hundred kilometers of Pluto’s atmosphere, as seen in both forward scattering obser- vations and solar / stellar occultations (Stern et al., 2015; Gladstone et al., 2016). The haze appeared blue, which is likely due to Rayleigh scattering by small particles. However, it also featured a large high to low phase brightness ratio, indicative of large particles. These two observations combined point to the haze particles being fractal aggregates, drawing strong parallels between the Pluto haze and the hazes of Titan (Elliot, Ates, et al., 2003). Thus, studying the Pluto haze can greatly in- form comparisons of these two apparently disparate worlds. In addition, the haze particles can act as nucleation sites for condensable species in Pluto’s atmosphere, thereby directly a ff ecting atmospheric chemistry. In this work, we compare the observed haze extinction profiles with those calculated by microphysical models, thereby o ff ering insights into the major processes controlling the haze distribution. We describe our microphysical model in §3.3. In §3.4, we present our model re- sults, compare them to data, and discuss the impact of condensation on the haze distribution.
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Connecting planet formation and astrochemistry. Refractory carbon depletion leading to super-stellar C/O in giant planetary atmospheres

Connecting planet formation and astrochemistry. Refractory carbon depletion leading to super-stellar C/O in giant planetary atmospheres

abundance of relevant carbon and oxygen bearing molecular species are determined through a complex chemical kinetic code which includes both gas and grain surface chemistry. This is combined with a model for the abundance of the refractory dust grains to compute the total carbon and oxygen abundance in the protoplanetary disk available for incorporation into a planetary atmosphere. We include the effects of the refractory carbon depletion that has been observed in our solar system, and posit two models that would put this missing carbon back into the gas phase. This excess gaseous carbon then becomes important in determining the final planetary C/O because the gas disk now becomes more carbon rich relative to oxygen (high gaseous C/O). One model, where the carbon excess is maintained throughout the lifetime of the disk results in Hot Jupiters that have super-stellar C/O. The other model deposits the excess carbon early in the disk life and allows it to advect with the bulk gas. In this model the excess carbon disappears into the host star within 0.8 Myr, returning the gas disk to its original (sub-stellar) C/O, so the Hot Jupiters all exclusively have sub-stellar C/O. This shows that while the solids will tend to be oxygen rich, Hot Jupiters can have super-stellar C/O if a carbon excess can be maintained by some chemical processing of the dust grains. The atmospheric C/O of the super-Earths at larger radii are determined by the chemical interactions between the gas and ice phases of volatile species rather than the refractory carbon model. Whether the carbon and oxygen content of the atmosphere was accreted primarily by gas or solid accretion is heavily dependent on the mass of the atmosphere and where in the disk the growing planet accreted.
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Far UV Emissions of the Sun in Time: Probing Solar Magnetic Activity and Effects on Evolution of Paleo Planetary Atmospheres

Far UV Emissions of the Sun in Time: Probing Solar Magnetic Activity and Effects on Evolution of Paleo Planetary Atmospheres

We anticipate that these irradiance results will be important for the study of paleo-atmospheres of the Solar System plan- ets. In particular, preliminary analyses indicate that the high X-ray and EUV emission fluxes of the early Sun could have produced significant heating of the planetary exospheres and upper-atmospheres thus enhancing processes such as thermal escape. The early Sun’s strong FUV and UV fluxes penetrate further into the atmosphere and probably influenced the photo- chemistry of, e.g., methane and ammonia, which are important greenhouse gases. Thus, this study has strong implications for the evolution of the pre-biotic and Archean atmosphere of the Earth as well as for the early development of life on Earth and possibly on Mars.
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A chemical kinetics network for lightning and life in planetary atmospheres

A chemical kinetics network for lightning and life in planetary atmospheres

As mentioned above, electric discharges may also be an important source of energy driving the production of prebiotic species, and are ubiquitous throughout the gas giants. Discharges in the form of lightning are known to occur within our solar system, on Earth, Jupiter ( Little et al. 1999 ) , Saturn ( Dyudina et al. 2007 ) , Uranus ( Zarka & Pedersen 1986 ) , and Neptune ( Gurnett et al. 1990 ) . There are some indications of lightning discharges on Venus ( Taylor et al. 1979 ) , and possibly also in Titan ’ s nitrogen chemistry ( Borucki et al. 1984 ) , although these traces are still tentative. Lightning is hypothesized to occur on exoplanets ( Aplin 2013; Helling et al. 2013 ) and brown dwarfs ( Helling et al. 2013; Bailey et al. 2014 ) . Simulated plasma discharges initiated within Jupiter- like gas compositions suggest that lightning on Jupiter may produce a signi fi cant amount of trace gases ( Borucki et al. 1985 ) . The comparison between experimental rates of the  production of organic compounds in high-temperature plasmas to chemical equilibrium models is unsurprisingly poor ( Scattergood et al. 1989 ) , and indicates that a chemical kinetics approach will be important in explaining the results of these experiments.  Chemical kinetics seems  to be necessary for exploring any of these pathways to the formation of prebiotic species.
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A miniature sensor for electrical field measurements in dusty planetary atmospheres

A miniature sensor for electrical field measurements in dusty planetary atmospheres

Abstract. Dusty phenomena such as regular wind-blown dust, dust storms, and dust devils are the most important, currently active, geological processes on Mars. Electric fields larger than 100 kV/m have been measured in terrestrial dusty phenomena. Theoretical calculations predict that, close to the surface, the bulk electric fields in martian dusty phenomena reach the breakdown value of the isolating properties of thin martian air of about a few 10 kV/m. The fact that martian dusty phenomena are electrically active has important implications for dust lifting and atmospheric chemistry. Electric field sensors are usually grounded and distort the electric fields in their vicinity. Grounded sensors also produce large errors when subject to ion currents or impacts from clouds of charged particles. Moreover, they are incapable of providing information about the direction of the electric field, an important quantity. Finally, typical sensors with more than 10 cm of diameter are not capable of measuring electric fields at distances as small as a few cm from the surface. Measurements this close to the surface are necessary for studies of the effects of electric fields on dust lifting. To overcome these shortcomings, we developed the miniature electric-field sensor described in this article.
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