scholarly journals The effect of high nitrogen pressures on the habitable zone and an appraisal of greenhouse states

2020 ◽  
Vol 494 (1) ◽  
pp. 259-270 ◽  
Author(s):  
Ramses M Ramirez
Keyword(s):  
Main Tool ◽  
Nitrogen Pressure ◽  
Spectroscopic Observation ◽  
Atmospheric Composition ◽  
Balance Model ◽  
Threshold Temperature ◽  
Habitable Zone ◽  
High Background ◽  
M Stars ◽  
Planetary Albedo

ABSTRACT The habitable zone (HZ) is the main tool that mission architectures utilize to select potentially habitable planets for follow-up spectroscopic observation. Given its importance, the precise size and location of the HZ remains a hot topic, as many studies, using a hierarchy of models, have assessed various factors including: atmospheric composition, time, and planetary mass. However, little work has assessed how the HZ changes with variations in background nitrogen pressure, which is directly connected to the habitability and life-bearing potential of planets. Here, I use an advanced energy balance model with clouds to show that our Solar system's HZ is ∼0.9–1.7 au, assuming a 5-bar nitrogen background pressure and a maximum 100 per cent cloud cover at the inner edge. This width is ∼20 per cent wider than the conservative HZ estimate. Similar extensions are calculated for A–M stars. I also show that cooling clouds/hazes and high background pressures can decrease the runaway greenhouse threshold temperature to ∼300 K (or less) for planets orbiting any star type. This is because the associated increase in planetary albedo enables stable climates closer to the star, where rapid destabilization can be triggered from a lower mean surface temperature. Enhanced longwave emission for planets with very high stratospheric temperatures also permits stable climates at smaller orbital distances. The model predicts a runaway greenhouse above ∼330 K for planets orbiting the Sun, which is consistent with previous work. However, moist greenhouses only occur for planets orbiting A-stars.

scholarly journals Warm Paleocene/Eocene climate as simulated in ECHAM5/MPI-OM

2009 ◽  
Vol 5 (3) ◽  
pp. 1297-1336 ◽  
Author(s):  
M. Heinemann ◽  
J. H. Jungclaus ◽  
J. Marotzke
Keyword(s):  
Temperature Difference ◽  
Radiative Forcing ◽  
Co2 Concentration ◽  
The Arctic ◽  
Balance Model ◽  
Proxy Data ◽  
Reference Simulation ◽  
Low Latitudes ◽  
Planetary Albedo ◽  
Temperature Proxy

Abstract. We investigate the late Paleocene/early Eocene (PE) climate using the coupled atmosphere-ocean-sea ice model ECHAM5/MPI-OM. The surface in our PE control simulation is on average 297 K warm and ice-free, despite a moderate CO2 concentration of 560 ppm. Compared to a pre-industrial reference simulation (PR), low latitudes are 5 to 8 K warmer, while high latitudes are up to 40 K warmer. This high-latitude amplification is in line with proxy data, yet a comparison to sea surface temperature proxy data suggests that the Arctic surface temperatures are still too low. To identify the mechanisms that cause the PE-PR temperature difference, we fit a zero-dimensional energy balance model to the ECHAM5/MPI-OM results. Doubled pCO2 in PE compared to PR, increased atmospheric water vapour, and a slightly increased longwave cloud radiative forcing together cause about 2/3 of the PE-PR temperature difference; planetary albedo changes cause about 1/3. Our results support the hypothesis that local radiative effects as well as topographic changes, rather than increased meridional heat transports, were responsible for the "equable" PE climate.

scholarly journals Numerical Prognosis of Dispersion and Transport of Pollutants in Romania, Based on Emissions of Pollutants

2019 ◽  
Vol 13 (1) ◽  
pp. 191-200
Author(s):  
Bogdan Alexandru Maco ◽  
Nicoleta Ionac ◽  
George Tudorache
Keyword(s):  
Air Quality ◽  
National Level ◽  
Main Tool ◽  
Atmospheric Composition ◽  
Numerical Dispersion ◽  
Air Quality Model ◽  
Quality Model ◽  
Gravimetric Data ◽  
Environment Agency ◽  
Physical And Chemical

Abstract Air pollution is one of the major problems of mankind, transport of pollutants extending far beyond the borders of the countries where they were produced, causing unpredictable, direct and indirect changes of the environment. The main tool for the study of this phenomenon consists of mathematical modeling of complex physical and chemical phenomena involved. In practice, air emissions are estimated on basis of measurements taken from selected sources being representative of the major categories and types. At national level, the Air Quality Evaluation Center (CECA) provides regular reports to the European Environment Agency (EEA) or the European Commission as requirements of Romania’s lawful duties in air quality domain. The registry of emissions TNO/ MACC (Netherlands Organisation for Applied Scientific Research/ Monitoring Atmospheric Composition and Climate) contains emissions inventories which have been homogenized and checked in advance and obtained from emissions officially reported at sectoral level for each country. In this study, for the analysis of the weather numerical dispersion and transport of pollutants, it has been used the numerical air quality model WRF-CHEM version 3.5, centered over Romania, at the spatial resolution of 10 km, using as input data the TNO emission database for 2009. By interpolating values from the regular grid of the TNO database with the WRF-CHEM model 3.5 grid, monthly average values were obtained for each day of the week, for any parameter considered. Preliminary results obtained for different pollutants (for example: PM10, O3) confirm the need to validate these results by implementing and integrating air quality forecasting model by assimilating different types of measurements (data model, gravimetric data observations, etc.).

scholarly journals Exoplanet secondary atmosphere loss and revival

2020 ◽  
Vol 117 (31) ◽  
pp. 18264-18271 ◽  
Author(s):  
Edwin S. Kite ◽  
Megan N. Barnett
Keyword(s):  
Molecular Weight ◽  
Simple Model ◽  
Solar System ◽  
High Molecular Weight ◽  
Habitable Zone ◽  
Magma Ocean ◽  
Early Loss ◽  
High Molecular Weight Species ◽  
M Stars ◽  
Volcanic Outgassing

The next step on the path toward another Earth is to find atmospheres similar to those of Earth and Venus—high–molecular-weight (secondary) atmospheres—on rocky exoplanets. Many rocky exoplanets are born with thick (>10 kbar) H2-dominated atmospheres but subsequently lose their H2; this process has no known Solar System analog. We study the consequences of early loss of a thick H2atmosphere for subsequent occurrence of a high–molecular-weight atmosphere using a simple model of atmosphere evolution (including atmosphere loss to space, magma ocean crystallization, and volcanic outgassing). We also calculate atmosphere survival for rocky worlds that start with no H2. Our results imply that most rocky exoplanets orbiting closer to their star than the habitable zone that were formed with thick H2-dominated atmospheres lack high–molecular-weight atmospheres today. During early magma ocean crystallization, high–molecular-weight species usually do not form long-lived high–molecular-weight atmospheres; instead, they are lost to space alongside H2. This early volatile depletion also makes it more difficult for later volcanic outgassing to revive the atmosphere. However, atmospheres should persist on worlds that start with abundant volatiles (for example, water worlds). Our results imply that in order to find high–molecular-weight atmospheres on warm exoplanets orbiting M-stars, we should target worlds that formed H2-poor, that have anomalously large radii, or that orbit less active stars.

scholarly journals Evaluating the effect of four unknown parameters included in a latitudinal energy balance model on the habitability of exoplanets

2020 ◽  
Vol 29 (1) ◽  
pp. 231-250
Author(s):  
Majid Bahraminasr ◽  
S. Javad Jafarzadeh ◽  
Fatemeh Montazeri ◽  
Atila Poro ◽  
Soroush Sarabi
Keyword(s):  
Energy Balance ◽  
Energy Balance Model ◽  
Balance Model ◽  
Physical Parameters ◽  
Habitable Zone ◽  
Unknown Parameters ◽  
The Impact ◽  
Excellent Tool ◽  
Simulation Time ◽  
Diurnal Period

AbstractAmong different models for determining the habitable zone (HZ) around a star, a Latitudinal Energy Balance Model (LEBM) is very beneficial due to its parametricity which keeps a good balance between complexity and simulation time. This flexibility makes the LEBM an excellent tool to assess the impact of some key physical parameters on the temperature and the habitability of a planet. Among different physical parameters, some of them, up until now, cannot be determined by any method such as the planet’s spin obliquity, diurnal period, ocean-land ratio, and pressure level. Here we apply this model to study the effect of these unknown parameters on the habitability of three exoplanets located in the inner, outer, and middle of their optimistic HZ. Among the examined parameters, the impact of pressure is more straightforward. It has a nearly direct relation with temperature and also with the habitability in the case of a cold planet. The effect of other parameters is discussed with details. To quantify the impact of all these unknown parameters we utilize a statistical interface which provides us with the conditional probability on habitability status of each planet.

scholarly journals Calibration and evaluation of a high-resolution surface mass-balance model for Paakitsoq, West Greenland

2012 ◽  
Vol 58 (212) ◽  
pp. 1047-1062 ◽  
Author(s):  
Alison F. Banwell ◽  
Ian C. Willis ◽  
Neil S. Arnold ◽  
Alexandra Messerli ◽  
Cameron J. Rye ◽  
...  
Keyword(s):  
Mass Balance ◽  
Model Performance ◽  
Greenland Ice Sheet ◽  
Balance Model ◽  
Threshold Temperature ◽  
Mass Balance Model ◽  
Surface Mass ◽  
West Greenland ◽  
Landsat 7 ◽  
Normalized Difference Snow Index

AbstractModelling the hydrology of the Greenland ice sheet, including the filling and drainage of supraglacial lakes, requires melt inputs generated at high spatial and temporal resolution. Here we apply a high spatial (100 m) and temporal (1 hour) mass-balance model to a 450 km2 subset of the Paakitsoq region, West Greenland. The model is calibrated by adjusting the values for parameters of fresh snow density, threshold temperature for solid/liquid precipitation and elevation-dependent precipitation gradient to minimize the error between modelled output and surface height and albedo measurements from three Greenland Climate Network stations for the mass-balance years 2000/01 and 2004/05. Bestfit parameter values are consistent between the two years at 400 kg m-3, 2°C and +14% (100 m)-1, respectively. Model performance is evaluated, first, by comparing modelled snow and ice distribution with that derived from Landsat-7 ETM+ satellite imagery using normalized-difference snow index classification and supervised image thresholding; and second, by comparing modelled albedo with that retrieved from the MODIS sensor M0D10A1 product. Calculation of mass-balance components indicates that 6% of surface meltwater and rainwater refreezes in the snowpack and does not become runoff, such that refreezing accounts for 31% of the net accumulation.

scholarly journals High-resolution reflection spectra for Proxima b and Trappist-1e models for ELT observations

2019 ◽  
Author(s):  
Z Lin ◽  
L Kaltenegger
Keyword(s):  
High Resolution ◽  
Reflection Spectra ◽  
Habitable Zone ◽  
Climate Indicators ◽  
Reflected Light ◽  
Earth Like Planets ◽  
M Stars ◽  
Large Telescopes ◽  
Host Stars ◽  
Absorption Features

ABSTRACT The closest stars that harbor potentially habitable planets are cool M-stars. Upcoming ground- and space-based telescopes will be able to search the atmosphere of such planets for a range of chemicals. To facilitate this search and to inform upcoming observations, we model the high-resolution reflection spectra of two of the closest potentially habitable exoplanets for a range of terrestrial atmospheres and surface pressures for active and inactive phases of their host stars for both oxic and anoxic conditions: Proxima b, the closest potentially habitable exoplanet, and Trappist-1e, one of 3 Earth-size planets orbiting in the Habitable Zone of Trappist-1. We find that atmospheric spectral features, including biosignatures like O2 in combination with a reduced gas like CH4 for oxic atmospheres, as well as climate indicators like CO2 and H2O for all atmospheres, show absorption features in the spectra of Proxima b and Trappist-1e models. However for some features like oxygen, high-resolution observations will be critical to identify them in a planet's reflected flux. Thus these two planets will be among the best targets for upcoming observations of potential Earth-like planets in reflected light with planned Extremely Large Telescopes.

scholarly journals The diurnal Energy Balance Model (dEBM): A convenient surface mass balance solution for ice sheets in Earth System modeling

2020 ◽  
Author(s):  
Uta Krebs-Kanzow ◽  
Paul Gierz ◽  
Christian B. Rodehacke ◽  
Shan Xu ◽  
Hu Yang ◽  
...  
Keyword(s):  
Energy Balance ◽  
Mass Balance ◽  
System Modeling ◽  
Ice Sheets ◽  
Atmospheric Composition ◽  
Balance Model ◽  
Surface Mass Balance ◽  
Earth System ◽  
Earth System Modeling ◽  
Surface Mass

Abstract. The surface mass balance scheme dEBM (diurnal Energy Balance Model) provides a novel interface between the atmosphere and land ice for Earth System modeling, which is based on the energy balance of glaciated surfaces. In contrast to empirical schemes, dEBM accounts for changes in the Earth's orbit and atmospheric composition. The scheme only requires monthly atmospheric forcing (precipitation, temperature, shortwave and longwave radiation, and cloud cover). It is also computationally inexpensive, which makes it particularly suitable to investigate the ice sheets' response to long-term climate change. After calibration and validation, we analyze the surface mass balance of the Greenland Ice Sheet (GrIS) based on climate simulations representing two warm climate states: a simulation of the Mid Holocene (approximately 6000 years before present) and a climate projection based on an extreme emission scenario which extends to the year 2100. The former period features an intensified summer insolation while the 21st century is characterized by reduced outgoing long wave radiation. Specifically, we investigate whether the temperature-melt relationship, as used in empirical temperature-index methods, remains stable under changing insolation and atmospheric composition. Our results indicate that the temperature-melt relation is sensitive to changes in insolation on orbital time scales but remains mostly invariant under the projected warming climate of the 21st century.

scholarly journals Soccer games and record-breaking PM<sub>2.5</sub> pollution events in Santiago, Chile

2019 ◽  
Author(s):  
Rémy Lapere ◽  
Laurent Menut ◽  
Sylvain Mailler ◽  
Nicolás Huneeus
Keyword(s):  
Air Quality ◽  
Fine Particulate Matter ◽  
Atmospheric Composition ◽  
Emergency Plans ◽  
High Background ◽  
Large Cities ◽  
Residential Heating ◽  
Good Proxy ◽  
Pollution Events

Abstract. In wintertime, high background concentrations of atmospheric fine particulate matter (PM2.5) are commonly observed in the metropolitan area of Santiago, Chile. Hourly peaks can be very strong, up to ten times average levels, but have barely been studied so far. Based on atmospheric composition measurements and chemistry-transport modeling (WRF-CHIMERE), the chemical signature of sporadic skyrocketing wintertime PM2.5 peaks is analyzed. This signature and the timing of such extreme events traces their origin back to massive barbecue cooking by Santiago's inhabitants during international soccer games. The peaks end up evacuated outside Santiago after a few hours but trigger emergency plans for the next day. Decontamination plans in Santiago focus on decreasing traffic, industrial and residential heating emissions. Thanks to the air quality network of Santiago, this study shows that cultural habits such as barbecue cooking also need to be taken into account. For short-term forecast and emergency management, cultural events such as soccer games seem a good proxy to prognose possible PM2.5 peak events. Not only this result can have an informative value for the Chilean authorities, but a similar methodology could also be reproduced for other cases throughout the world in order to estimate the burden on air quality of cultural habits. In particular, the present study shows that investigating the atmospheric composition in large cities during major events is key for the design of effective air pollution mitigation policies.

Earth-like worlds on eccentric orbits: excursions beyond the habitable zone

2002 ◽  
Vol 1 (1) ◽  
pp. 61-69 ◽  
Author(s):  
Darren M. Williams ◽  
David Pollard
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Three Dimensional ◽  
Balance Model ◽  
Seasonal Temperature ◽  
Habitable Zone ◽  
One Dimensional ◽  
Climate Stability ◽  
Eccentric Orbits

Many of the recently discovered extrasolar giant planets move around their stars on highly eccentric orbits, and some with e [ges ] 0·7. Systems with planets within or near the habitable zone (HZ) will possibly harbour life on terrestrial-type moons if the seasonal temperature extremes resulting from the large orbital eccentricities of the planets are not too severe. Here we use a three-dimensional general-circulation climate model and a one-dimensional energy-balance model to examine the climates of either bound or isolated earths on extremely elliptical orbits near the HZ. While such worlds are susceptible to large variations in surface temperature, long-term climate stability depends primarily on the average stellar flux received over an entire orbit, not the length of the time spent within the HZ.

scholarly journals Susceptibility of planetary atmospheres to mass loss and growth by planetesimal impacts: the impact shoreline

2019 ◽  
Author(s):  
M C Wyatt ◽  
Q Kral ◽  
C A Sinclair
Keyword(s):  
Orbital Period ◽  
Planetary Atmospheres ◽  
High Mass ◽  
Habitable Zone ◽  
Similar Dependence ◽  
Low Mass ◽  
M Stars ◽  
The Impact ◽  
Lower Luminosity ◽  
Impact Outcome

Abstract This paper considers how planetesimal impacts affect planetary atmospheres. Atmosphere evolution depends on the ratio of gain from volatiles to loss from atmosphere stripping fv; for constant bombardment, atmospheres with fv < 1 are destroyed in finite time, but grow linearly with time for fv > 1. An impact outcome prescription is used to characterise how fv depends on planetesimal impact velocities, size distribution and composition. Planets that are low mass and/or close to the star have atmospheres that deplete in impacts, while high mass and/or distant planets grow secondary atmospheres. Dividing these outcomes is an fv = 1 impact shoreline analogous to Zahnle & Catling’s cosmic shoreline. The impact shoreline’s location depends on assumed impacting planetesimal properties, so conclusions for the atmospheric evolution of a planet like Earth with fv ≈ 1 are only as strong as those assumptions. Application to the exoplanet population shows the gap in the planet radius distribution at ∼1.5R⊕ is coincident with the impact shoreline, which has a similar dependence on orbital period and stellar mass to the observed gap. Given sufficient bombardment, planets below the gap would be expected to lose their atmospheres, while those above could have atmospheres enhanced in volatiles. The level of atmosphere alteration depends on the total bombardment a planet experiences, and so on the system’s (usually unknown) other planets and planetesimals, though massive distant planets would have low accretion efficiency. Habitable zone planets around lower luminosity stars are more susceptible to atmosphere stripping, disfavouring M stars as hosts of life-bearing planets if Earth-like bombardment is conducive to the development of life.

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