Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [154]-162).

COMMA-LIM (Cologne Model of the Middle Atmosphere - Leipzig Institute for Meteorology) ist ein 3D-mechanistisches Gitterpuktsmodell, welches sich von ca. 0 bis 135 km in logarhitmischen Druckkordinaten z = -H ln(p=p0) erstreckt, wobei H=7 km und p0 den Referenzdruck am unteren Rand bezeichnet. Die vertikale Auflösung von COMMA-LIM wurde auf 48 Schichten erhöht. Zugleich wurde die Beschreibung des Strahlungsprozesses verbessert, zusammen mit den Beiträgen zur Temperaturbilanz durch atmosphärische Wellen und Turbulenz. Weitere Veränderungen betreffen die numerische Realisation der horizontalen Diffusion und des Filterproblems. Die Beschreibung ist unterteilt in den dynamischen Teil und die Strahlungsbeträge. Die jahreszeitlichen Klimatologien werden vorgestellt und diskutiert. / COMMA-LIM (Cologne Model of the Middle Atmosphere - Leipzig Institute for Meteorology) is a 3D-mechanistic gridpoint model extending up from 0 to 135 km with a logharithmic vertical coordinate z = -H ln(p=p0), where H=7 km and p0 is the reference pressure at lower boundary. The resolution of the 24 layer version has been increased to 48 layers and several improvements are made in the parameterisation of radiative processes, heating/cooling due to atmospheric waves and turbulence, as well as in the numerical realization of the horizontal diffusion and filtering. This description is divided into the section describing the changes in the dynamical part and the modifications in radiation routines. After all, the seasonal climatologies will be shown and discussed to demonstrate what the COMMA-LIM is capable of reproducing.

No description available.

This thesis presents the results of calculating model atmospheres for the accretion column of a magnetic white dwarf. A basic stellar atmosphere calculation is refined to model the specific conditions at the base of an accretion column. Calculated spectra for a variety of different input conditions are shown. The calculated spectra are fitted with black body spectra in order to ascertain the errors associated with black body fitting of observed spectra. Simulated lightcurves are calculated using these model atmosphere spectra. The resultant lightcurves are folded through the EXOSAT (European X-ray Observatory Satellite) detectors and used to fit lightcurves from the magnetic polar system AM Herculis. Following the assumption that a thin accretion disc around a supermassive black hole is the central power source for active galactic nuclei (AGN's) a large grid of model atmospheres is calculated. This grid is then used to calculate the spectrum from such a disc.

Observations from Cassini VIMS and ISS show localized but extensive surface brightenings in the wake of the 2010 September cloudburst. Four separate areas, all at similar latitude, show similar changes: Yalaing Terra, Hetpet Regio, Concordia Regio, and Adiri. Our analysis shows a general pattern to the time-sequence of surface changes: after the cloudburst the areas darken for months, then brighten for a year before reverting to their original spectrum. From the rapid reversion timescale we infer that the process driving the brightening owes to a fine-grained solidified surface layer. The specific chemical composition of such solid layer remains unknown. Evaporative cooling of wetted terrain may play a role in the generation of the layer, or it may result from a physical grain-sorting process.

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An observational program was designed for systematic spatial and temporal monitoring of the Jovian atmosphere at several wavelengths chosen for their different absorptive properties. The weak broadband (5Å/pixel) CH₄ absorptions (6190 and 7270Å) probe the deep (2-4 bars) cloud layer while the stronger band at 8900Å probes the upper 400-600 mbars. The high resolution (~50mÅ/pixel) 3-0 H₂ quadrupole wavelengths probe to about 1-2 bars. The gradual increase in the measured equivalent widths of the H₂ quadrupole lines from the east to west limb is most likely indicative of a diurnal change in the vertical cloud structure. Such a variation is consistent with the properties of a convective layer driven by internal heat, with solar heat deposited at the top. The CH₄ data from the same time period was modelled for the south tropical zone. Since these absorptions are sensitive to several atmospheric layers it is difficult to separate the effects of the various cloud parameters on the [(I/F)(band)]/[(I/F)(cont)] values. There are no obvious limb to limb variations in these bands but several cloud parameters may be changing simultaneously, introducing compensating affects on the [(I/F)(band)]/[(I/F)(cont)] values. The two limbs may not, therefore, appear significantly different even if they are representative of substantially different cloud structures. The June 1983 H₂ data has been modelled at seven different latitudes and cloud structure differences are indicated. The average models representing the belt regions require somewhat thinner optical depths for the upper ammonia cloud (τ(cl) = 3-4.5) than the zones (τ(cl) = 5.5-6.5) or the equatorial region (τ(cl) = 6.5-7). These data also provide some constraints on the thermodynamic state of the hydrogen. A model atmosphere with only "normal" hydrogen (ortho-H₂ to para-H₂ of 3:1) is not able to fit both of the 3-0 lines simultaneously. Model atmospheres with all of the hydrogen in a state of equilibrium fit the two lines much better. Models with small amounts of disequilibrium hydrogen in the upper atmosphere also provide reasonable average fits to our H₂ data and cannot be easily distinguished from those that incorporate only equilibrium hydrogen at all levels or from those which incorporate "normal" in the top 300 mbars of the Jovian atmosphere.

This is a reprint from the Meteorological Journal, March, 1895.