Browsing by Subject "atmosphere"

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Contributions to absorption line weakening in the Earth's atmosphere
(2008) Penner, Kyle; Allende Prieto, Carlos; Shardha Jogee
Daytime skylight is an imperfect representation of the solar spectrum. Scattering of light in the Earth’s atmosphere changes the depths of solar absorption lines. This scattering is due to either molecules or dust grains in the Earth’s atmosphere. Addi- tionally, ground-albedo, the reflection of sunlight from the Earth’s surface back into the atmosphere, may play an important role in diluting the strength of absorption lines. The relative importance of each process is not understood – some studies suggest that ground-albedo is not important, while others indicate that it is significant. We exam- ine the filling-in of absorption lines as a function of angular separation from the Sun, replicating previous measurements with a much richer dataset; because we have line data for the Sun’s entire optical spectrum, we more clearly determine what processes are important.
DSMC Modeling Of Gasdynamics, Radiation And Fine Particulates In Ionian Volcanic Jets
(2003-05) Zhang, J.; Goldstein, D. B.; Varghese, P. L.; Gimelshein, N. E.; Gimelshein, S. F.; Levin, D. A.; Trafton, L.; Zhang, J.; Goldstein, D. B.; Varghese, P. L.; Trafton, L.
First Results from the GPS Atmosphere Sounding Experiment TOR Aboard the Terrasar-X Satellite
(2011) Beyerle, G.; Grunwaldt, L.; Heise, S.; Kohler, W.; Konig, R.; Michalak, G.; Rothacher, M.; Schmidt, T.; Wickert, J.; Tapley, B. D.; Giesinger, B.; Tapley, B. D.
GPS radio occultation events observed between 24 July and 17 November 2008 by the IGOR occultation receiver aboard the TerraSAR-X satellite are processed and analyzed. The comparison of 15 327 refractivity profiles with collocated ECMWF data yield a mean bias between zero and -0.30% at altitudes between 5 and 30 km. Standard deviations decrease from about 1.4% at 5 km to about 0.6% at 10 km altitude, however, increase significantly in the upper stratosphere. At low latitudes mean biases and standard deviations are larger, in particular in the lower troposphere. The results are consistent with 15 159 refractivity observations collected during the same time period by the BlackJack receiver aboard GRACE-A and processed by GFZ's operational processing system. The main difference between the two occultation instruments is the implementation of open-loop signal tracking in the IGOR (TerraSAR-X) receiver which improves the tropospheric penetration depth in terms of ray height by about 2 km compared to the conventional closed-loop data acquired by BlackJack (GRACE-A).
Formation and Aging of Secondary Organic Aerosol from Toluene: Changes in Chemical Composition, Volatility, and Hygroscopicity
(2015) Ruiz, L. Hildebrandt; Paciga, A. L.; Cerully, K. M.; Nenes, A.; Donahue, N. M.; Pandis, S. N.; Ruiz, L. Hildebrandt
Secondary organic aerosol (SOA) is transformed after its initial formation, but this chemical aging of SOA is poorly understood. Experiments were conducted in the Carnegie Mellon environmental chamber to form secondary organic aerosol (SOA) from the photo-oxidation of toluene and other small aromatic volatile organic compounds (VOCs) in the presence of NOx under different oxidizing conditions. The effects of the oxidizing condition on organic aerosol (OA) composition, mass yield, volatility, and hygroscopicity were explored. Higher exposure to the hydroxyl radical resulted in different OA composition, average carbon oxidation state (OSc), and mass yield. The OA oxidation state generally increased during photo-oxidation, and the final OA OSc ranged from -0.29 to 0.16 in the performed experiments. The volatility of OA formed in these different experiments varied by as much as a factor of 30, demonstrating that the OA formed under different oxidizing conditions can have a significantly different saturation concentration. There was no clear correlation between hygroscopicity and oxidation state for this relatively hygroscopic SOA.
Geographic and Seasonal Distributions of CO Transport Pathways and Their Roles in Determining CO Centers in the Upper Troposphere
(2012) Huang, L.; Fu, R.; Jiang, J. H.; Wright, J. S.; Luo, M.; Huang, L.; Fu, R.; Wright, J. S.
Past studies have identified a variety of pathways by which carbon monoxide (CO) may be transported from the surface to the tropical upper troposphere (UT); however, the relative roles that these transport pathways play in determining the distribution and seasonality of CO in the tropical UT remain unclear. We have developed a method to automate the identification of two pathways ('local convection' and 'advection within the lower troposphere (LT) followed by convective vertical transport') involved in CO transport from the surface to the UT. This method is based on the joint application of instantaneous along-track, co-located, A-Train satellite measurements. Using this method, we find that the locations and seasonality of the UT CO maxima in the tropics were strongly correlated with the frequency of local convective transport during 2007. We also find that the 'local convection' pathway (convective transport that occurred within a fire region) typically transported significantly more CO to the UT than the 'LT advection -> convection' pathway (advection of CO within the LT from a fire region to a convective region prior to convective transport). To leading order, the seasonality of CO concentrations in the tropical UT reflected the seasonality of the 'local convection' transport pathway during 2007. The UT CO maxima occurred over Central Africa during boreal spring and over South America during austral spring. Occurrence of the 'local convection' transport pathway in these two regions also peaked during these seasons. During boreal winter and summer, surface CO emission and convection were located in opposite hemispheres, which limited the effectiveness of transport to the UT. During these seasons, CO transport from the surface to the UT typically occurred via the 'LT advection -> convection' pathway.
Kepler-10 c: a 2.2 Earth Radius Transiting Planet in a Multiple System
(2011-11) Fressin, Francois; Torres, Guillermo; Desert, Jean-Michel; Charbonneau, David; Batalha, Natalie M.; Fortney, Jonathan J.; Rowe, Jason F.; Allen, Christopher; Borucki, William J.; Brown, Timothy M.; Bryson, Stephen T.; Ciardi, David R.; Cochran, William D.; Deming, Drake; Dunham, Edward W.; Fabrycky, Daniel C.; Gautier, Thomas N., III; Gilliland, Ronald L.; Henze, Christopher E.; Holman, Matthew J.; Howell, Steve B.; Jenkins, Jon M.; Kinemuchi, Karen; Knutson, Heather; Koch, David G.; Latham, David W.; Lissauer, Jack J.; Marcy, Geoffrey W.; Ragozzine, Darin; Sasselov, Dimitar D.; Still, Martin; Tenenbaum, Peter; Uddin, Kamal; Cochran, William D.
The Kepler mission has recently announced the discovery of Kepler-10 b, the smallest exoplanet discovered to date and the first rocky planet found by the spacecraft. A second, 45 day period transit-like signal present in the photometry from the first eight months of data could not be confirmed as being caused by a planet at the time of that announcement. Here we apply the light curve modeling technique known as BLENDER to explore the possibility that the signal might be due to an astrophysical false positive (blend). To aid in this analysis we report the observation of two transits with the Spitzer Space Telescope at 4.5 mu m. When combined, they yield a transit depth of 344 +/- 85 ppm that is consistent with the depth in the Kepler passband (376 +/- 9 ppm, ignoring limb darkening), which rules out blends with an eclipsing binary of a significantly different color than the target. Using these observations along with other constraints from high-resolution imaging and spectroscopy, we are able to exclude the vast majority of possible false positives. We assess the likelihood of the remaining blends, and arrive conservatively at a false alarm rate of 1.6 x 10(-5) that is small enough to validate the candidate as a planet (designated Kepler-10 c) with a very high level of confidence. The radius of this object is measured to be R-p = 2.227(-0.057)(+ 0.052) R-circle plus (in which the error includes the uncertainty in the stellar properties), but currently available radial-velocity measurements only place an upper limit on its mass of about 20 M-circle plus. Kepler-10 c represents another example (with Kepler-9 d and Kepler-11 g) of statistical "validation" of a transiting exoplanet, as opposed to the usual "confirmation" that can take place when the Doppler signal is detected or transit timing variations are measured. It is anticipated that many of Kepler's smaller candidates will receive a similar treatment since dynamical confirmation may be difficult or impractical with the sensitivity of current instrumentation.
Kepler-14B: A Massive Hot Jupiter Transiting An F Star in A Close Visual Binary
(2011-11) Buchhave, Lars A.; Latham, David W.; Carter, Joshua A.; Desert, Jean-Michel; Torres, Guillermo; Adams, Elisabeth R.; Bryson, Stephen T.; Charbonneau, David B.; Ciardi, David R.; Kulesa, Craig; Dupree, Andrea K.; Fischer, Debra A.; Fressin, Francois; Gautier, Thomas N., III; Gilliland, Ronald L.; Howell, Steve B.; Isaacson, Howard; Jenkins, Jon M.; Marcy, Geoffrey W.; McCarthy, Donald W.; Rowe, Jason F.; Batalha, Natalie M.; Borucki, William J.; Brown, Timothy M.; Caldwell, Douglas A.; Christiansen, Jessie L.; Cochran, William D.; Deming, Drake; Dunham, Edward W.; Everett, Mark; Ford, Eric B.; Fortney, Jonathan J.; Geary, John C.; Girouard, Forrest R.; Haas, Michael R.; Holman, Matthew J.; Horch, Elliott; Klaus, Todd C.; Knutson, Heather A.; Koch, David G.; Kolodziejczak, Jeffrey; Lissauer, Jack J.; Machalek, Pavel; Mullally, Fergal; Still, Martin D.; Quinn, Samuel N.; Seager, Sara; Thompson, Susan E.; Van Cleve, Jeffrey; Cochran, William D.
We present the discovery of a hot Jupiter transiting an F star in a close visual (0 ''.3 sky projected angular separation) binary system. The dilution of the host star's light by the nearly equal magnitude stellar companion (similar to 0.5 mag fainter) significantly affects the derived planetary parameters, and if left uncorrected, leads to an underestimate of the radius and mass of the planet by 10% and 60%, respectively. Other published exoplanets, which have not been observed with high-resolution imaging, could similarly have unresolved stellar companions and thus have incorrectly derived planetary parameters. Kepler-14b (KOI-98) has a period of P = 6.790 days and, correcting for the dilution, has a mass of M-p = 8.40(-0.34)(+ 0.35) M-J and a radius of R-p = 1.136(-0.054)(+ 0.073) R-J, yielding a mean density of rho(p) = 7.1 +/- 1.1 g cm(-3).
Modeling Io'S Sublimation-Driven Atmosphere: Gas Dynamics And Radiation Emission
(2009-12) Walker, A. C.; Gratiy, S. L.; Levin, D. A.; Goldstein, D. B.; Varghese, P. L.; Trafton, L. M.; Moore, C. H.; Stewart, B.; Walker, A. C.; Goldstein, D. B.; Varghese, P. L.; Trafton, L. M.; Moore, C. H.; Stewart, B.
Io's sublimation-driven atmosphere is modeled using the direct simulation Monte Carlo method. These rarefied gas dynamics simulations improve upon earlier models by using a three-dimensional domain encompassing the entire planet computed in parallel. The effects of plasma impact heating, planetary rotation, and inhomogeneous surface frost are investigated. Circumplanetary flow is predicted to develop from the warm subsolar region toward the colder night-side. The non-equilibrium thermal structure of the atmosphere, including vibrational and rotational temperatures, is also presented. Io's rotation leads to an asymmetric surface temperature distribution which is found to strengthen circumplanetary flow near the dusk terminator. Plasma heating is found to significantly inflate the atmosphere on both day- and night-sides. The plasma energy flux also causes high temperatures at high altitudes but permits relatively cooler temperatures at low altitudes near the dense subsolar point due to plasma energy depletion. To validate the atmospheric model, a radiative transfer model was developed utilizing the backward Monte Carlo method. The model allows the calculation of the atmospheric radiation from emitting/absorbing and scattering gas using an arbitrary scattering law and art arbitrary surface reflectivity. The model calculates the spectra in the v, vibrational band of SO(2) which are then compared to the observational data.
Tidal Synchronisation Of The Subdwarf B Binary Pg 0101+039
(2008-01) Geier, S.; Nesslinger, S.; Heber, U.; Randall, S. K.; Edelmann, H.; Green, E. M.; Edelmann, H.
Aims. Tidally locked rotation is a frequently applied assumption that helps to measure masses of invisible compact companions in close binaries. The calculations of synchronisation times are affected by large uncertainties, in particular for stars with radiative envelopes, calling for observational constraints. We aim to verify tidally locked rotation for the binary PG 0101+039, a subdwarf B star + white dwarf binary from its tiny (0.025%) light variations measured with the MOST satellite (Randall et al. 2005). Methods. Binary parameters were derived from the mass function, apparent rotation and surface gravity of PG 0101+039 assuming a canonical mass of 0.47 M-circle dot and tidally locked rotation. The light curve was then synthesised and was found to match the observed amplitude well. Results. We verified that the light variations are due to ellipsoidal deformation and that tidal synchronisation is established for PG 0101+039. Conclusions. We conclude that this assumption should hold for all sdB binaries with orbital periods of less than half a day. Hence the masses can be derived from systems that are too faint to measure tiny light variations.