Browsing by Author "Chamberlain, Joseph W."
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Item A comparative study of the early terrestrial atmospheres with interactive cloud formation(1990) Schmunk, Robert Bradley; Chamberlain, Joseph W.Due to their formation at about the same time in the same region of the early solar nebula, it is reasonable to assume that the primitive atmospheres of Earth, Mars and Venus were similar and that present-day differences have arisen as a result of their differing masses and incident solar fluxes. Using a radiative-convective model, we determine maximum and minimum carbon dioxide levels for the early atmospheres which are consistent with this assumption and with climatic conditions thought to have existed on the three terrestrial planets 4.0 billion years ago. Rather than employ the cloud-free atmosphere approach of earlier studies, we include an interactive water vapor transport and cloud formation scheme in the model. Due to uncertainties about the direction of cloud cover feedback, we treat cloud cover as fixed. For most cases examined, we set the cloud cover at 50%, but the effect of varying cloud cover is also explored.Item A Gauss-Seidel scheme for determining atmospheric temperature profiles in atmospheres with fixed water density distributions(1979) Essex, George Christopher R.; Chamberlain, Joseph W.The details of an algorithm which models the earth's atmosphere are presented. Specifically, it is an algorithm which produces the atmospheric temperature profile for this model atmosphere. The densities of the infrared active gases are left as free input parameters to facilitate the algorithm's use in climatological applications. The results of a computer program representation are discussed.Item Anisotropic scattering in the clouds of Venus(1977) Lestrade, John Patrick; Chamberlain, Joseph W.Many of the past analyses of the infrared spectra for Venus have adopted an isotropically scattering, homogeneous, atmospheric model. In this work, the anisotropic scattering phase function w* (1+a*cosO) has been used to demonstrate the effects of anisotropy on observable quantities. L.D.G. Young's equivalent width data for the 782 band has been used to calculate combinations of C2 specific abundance, pressure, continuum albedo, and anisotropy. These combinations give values for the atmospheric parameters of mean free path, aerosol number density, and total optical thickness of the clouds. Approximate similarity relations are employed to determine the "true" atmospheric parameters from the isotropic calculations. These extrapolated values agree well with the recent Venera probe data. The analysis indicates a total cloud optical thickness of 3 with a continuum single scattering albedo near unity. The derived aerosol number density, 45 cm^3, and mean free path, .76 km., liken the clouds of Venus to the strato-cirrus clouds of Earth.Item Artificially produced field-aligned short-scale striations(1980) Frey, Alfred; Gordon, William E.; Chamberlain, Joseph W.; Reiff, Patricia H.HF-radiowaves propagating in the ordinary mode and incident on an overdense ionosphere ( fHF < foF2 ) are known to excite parametric instabilities. Recent experiments showed that under the same conditions short-scale field-aligned striations are formed. The question concerning the interrelation of these two effects is not yet settled. An experiment was performed at the Arecibo Observatory during June 1977 with a 5 MHz radar installed on Guadeloupe island. The Guadeloupe radar had a line of sight perpendicular to the magnetic field lines in the F-region above Arecibo. The 5 MHz radar backscatter measurements from the region where these artificially produced field-aligned striations (AFAS) occur are used to get some insight into the geometry and the temporal behavior of AFAS. The energy density of the HF-field required to produce AFAS is estimated from the experimental data. Plasma-line data on the parametric instability obtained by the 43 MHz incoherent backscatter from the Arecibo Observatory is compared with the Guadeloupe 5 MHz radar data. Several mechanisms which were proposed to produce AFAS are discussed in the light of present and past experimental results.Item Differential change exchange cross sections for collisions of HE++ ions with H atoms(1983) Day, Amelia; Lane, Neal F.; Stebbings, Ronald F.; Chamberlain, Joseph W.Differential charge exchange cross sections are presented for ^4He^++ incident on an H(ls) atom for projectile energies of 3, 8, and 2 keV. A molecular state basis and straight line impact parameter formalism are used in the semiclassical eikonal approximation. Calculations were made with a ten state basis modified by Bates and McCarroll plane-wave translational factors and with an unmodified four state basis. Only cross sections corresponding to electron transfer into He+ (n = 2) states are included. Large and small angle oscillations are examined in terms of a diffractive scattering process. These results are consistent with other theoretical calculations.Item Jovian meteorology from Voyager 1: A diagnostic assessment of zonal thermal winds from Iris data(1980) Allison, Michael David; Chamberlain, Joseph W.; Few, Arthur A.; Talbot, Raymond J.The Voyager 1 near-encounter infrared data for Jupiter's atmosphere yield a measure of the temperature as a function of latitude and pressure level. These measurements are applied to the computation of the zonal thermal wind field above the cloud deck. The results are compared with the imaging measurements of the zonal winds at the cloud level and tentatively suggest that the thermal field is correlated with the jet stream system and in the sense required to reduce the strength of the jets with height. The possible dynamical implications of certain discrepancies in this picture are discussed. Also the variation of the standard deviation of the tropospheric temperature with latitude is discussed as a possible diagnostic indicator, of meridional momentum flux.Item Solar radiation pressure perturbations on satellite hydrogen atoms in the Earth's exosphere(1981) Stentz, Henry Valentine; Chamberlain, Joseph W.; Dessler, A. J.; Dufour, Reginald J.The following study investigates the effects of radiation pressure on H-atoms in the earth's exosphere. The exosphere is regarded as collisionless, permitting the atoms to be treated as particles in orbit about the earth obeying the laws of celestial mechanics. Attention is restricted to a class of atoms called satellites, whose initial orbital parameters place them in Keplerian satellite orbits, as distinguished from captive atoms whose orbits intersect the exobase (ballistic particles) and those which escape on hyperbolic trajectories. The evolution of these satellite orbits under the perturbing force of radiation pressure is determined by numerically integrating the classical perturbation equations for the orbital elements. These equations express the rates of change of the standard orbital elements in terms of the other elements and the vector components of a perturbing force. Results are presented graphically and compared with analytical results from a paper by Chamberlain (1979).Item The velocities of HF-induced short scale striations(1981) Coster, A. J. (Anthea J.); Gordon, William E.; Chamberlain, Joseph W.; Cloutier, Paul A.Short scale striations are among the phenomena that occur when the ionosphere is heated by high frequency (HF) radio waves with ordinary mode polarization. These striations are electron density irregularities aligned along the magnetic field lines in and near the heated region of the ionosphere. They are a direct consequence of the heating and disappear within seconds after the heater has been turned off. The striations are detected to be moving in the heated region. Experiments were performed in June 1977 to investigate short scale striations. The experiments combined the use of a portable 5 MHz radar located on the island of Guadeloupe with heating facilities at the Arecibo Observatory. The 5 MHz radar had a line of sight that was orthogonal to the magnetic field lines in the F region above Arecibo and was used to detect the striations and their velocities. The 43 MHz radar at Arecibo was used for additional diagnostics. Varying the power of the HF radio wave did not appear to affect the striation velocities. Instead, their velocities appeared to be well correlated with general F-region ionization drifts. On two evenings, shortly after ionospheric sunset, dramatic changes in the striation velocities were observed. These F-region velocity disturbances occur in conjunction with the intensification of existing sporadic-E regions. Only during these disturbed time periods were reflections from sporadic E detected at greater than 5 MHz. A mechanism whereby the sporadic-E regions cause the alternate coupling and decoupling of the E and F regions in the early evening hours is presented. This mechanism can explain changes in local F-region electric fields which would cause the velocity disturbances.Item Thermal response to ozone fluctuations in the stratosphere(1978) Stanulonis, Stanley; Chamberlain, Joseph W.V/e have investigated the extent to which temperature fluctuations in the stratosphere, at low-latitude, are controlled by O3 absorption of solar and ground radiation. From a one dimensional model, we calculated the expected local heating due to a local O3 increase. The measured thermal response at different heights then allows us to estimate the local fluctuations in the O3 abundance, which in turn yields a correlation between the total measured O3 fluctuations and that expected from the local temperature fluctuations. Thus we compared the theoretical expectation of AT versus ACOgl with a regression analysis of the total O3 and local radiosonde temperature at 1, 5, 3, 2, and 1 mb for four low-latitude stations. The expected total O3 fluctuations are comparable to the observed variations of total O3, suggesting therefore, that O3 has important controlling influence on the local temperature fluctuations in the stratosphere.