First proposed by Twomey, the aerosol first indirect effect hypothesizes that increased aerosol concentration leads to a larger number of cloud condensation nuclei, and therefore smaller but more numerous cloud droplets, which results in greater reflection of incoming solar radiation. It is known that this phenomenon has a net effect to cool the Earth radiatively and offset a substantial amount of the warming caused by the increasing of greenhouse gases. However, the magnitude of this effect has been very uncertain. For example, discrepancies of more than a factor of 2 have been reported among various observational results. This uncertainty is a major hurdle in advancing our understanding of how humans have altered, and may in the future alter the Earth's climate. One of the difficulties in deriving the magnitude of this effect from observational data arises from the fact that the aerosol abundance often varies coherently with meteorological conditions, which makes it extremely hard to distinguish between the changes in cloud microphysical parameters caused by varying aerosol concentration and by varying meteorological conditions. Therefore, the goal of this study is to find a reliable method to extract the real strength and to narrow the uncertainty in the estimates of the indirect radiative effect of aerosols. To achieve this goal, first, a satellite visible/near-infrared algorithm is developed to retrieve cloud optical depth and effective radius simultaneously at solar wavelengths (0.63 and 1.61 mm), and a satellite microwave algorithm is developed to retrieve liquid water path in the microwave range (19 and 37 GHz). Using these algorithm we derive cloud microphysical variables in relation to the aerosol first indirect effect. Second, a drizzle index is introduced to discriminate the drizzle clouds from non-drizzle clouds from satellite, which ensures our estimation of the first indirect effect not being contaminated by precipitation related processes. Third, using an analytical model, we have explained how the coherent nature between cloud depth and aerosol concentration as observed in the northeastern Pacific causes misidentification of the aerosol first indirect effect. Finally, we have further explained that the coherent variation between aerosol abundance and meteorological conditions is the major cause responsible for the large discrepancies among various observed values of the aerosol first indirect effect published in literature. We found that clouds in clean areas tend to deviate more from adiabatic process than clouds in polluted area near the coast, which causes an artifact term in commonly-used methods for deriving the aerosol first indirect effect. By introducing a new method capable of removing this artifact, the real strength of the aerosol first indirect effect is assessed over the region of Northeast Pacific. It shows that the magnitude of the aerosol first indirect effect measured by the new parameter is about half of that originally estimated by Twomey / A Dissertation submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Spring Semester, 2006. / Date of Defense: March 24, 2006. / Liquid Water Path, Cloud Effective Radius, Drizzle Detection, Radiative Transfer, Satellite Remote Sensing, Climate Change, Aerosol Indirect Effect / Includes bibliographical references. / Guosheng Liu, Professor Directing Dissertation; Kai-Sheng Song, Outside Committee Member; Robert G. Ellingson, Committee Member; Henry Fuelberg, Committee Member; Kwang-Yul Kim, Committee Member.

Inaug.-diss.--Halle-Wittenberg. / Lebenslauf. "Literaturnachweis": p. 62-63.

A synoptic and dynamic investigation of the jet stream reveals that in a transverse profile the maximum wind tends to lie along a pseudo-parabolic rather than a horizontal surface. The upwardfacing parabola is identified by a band of warm temperatures on the cyclonic side of the jet core and a band of cold temperatures on the anticyclonic side. The model is shown to be compatible with the thermal wind relationship.

Basic assumptions throughout the linear baroclinic model proposed by Fleagle (1957) for atmospheric motions are re-evaluated to assess applicability of the model for vertical motion computations in connection with potential-kinetic energy conversions in the stratosphere. It is found that some revisions are necessary to adequately describe very long wave activity, dominant at these levels, under the high stability conditions present. The source of the difficulties is found in the scaling of parameters of the zonal flow. Simple, but computationally awkward, corrections are suggested, and their affect partially traced through the model.

A spectral analysis of northward beat transport in the northern hemisphere was performed by the Fourier analysis method. This method was applied at 500 mb, 100 mb and 25 mb for five-day intervals from October 5, 1959 through March 28, 1960. A comparison of stratospheric warmings of this period with those of the previous year studied by Boville (1961), revealed that the heat transport could be accomplished mainly by wave numbers one and/or two. From 500-mb, 100-mb and 25-mb time-sections of northward heat transport, divergences were determined to calculate the local temperature time derivatives. These derivatives were in turn compared with the actual time-sections of mean temperature. This comparison showed that, due to strong convergence of northward heat transport, the winter stratosphere at high latitudes had a net ascending motion.

The applicability of the Curtis-Godson Approximation to calculations of infrared heating due to the 9.6-micron band of ozone is investigated. Satisfactory results are obtained at the bottom and top of the ozone layer while, at intermediate heights, the Approximation is not so successful. An explanation of this pattern is obtained by a crude application of criteria suggested by Plass (1960). With routine calculations made feasible by the use of the Approximation, the affect on heating rates of the distribution of ozone and temperature is investigated. The former appears as the more critical of the two parameters. A chart constructed for the graphical determination of flux divergence or heating rate is presented.

Values of the tritium concentration in precipitation collected at Ottawa in 1961 fluctuate by as much as a factor of 3 from one measurement to the next a few days later. The first attempt to determine what meteorological factors could be responsible for these fluctuations was to sort the storms for April and May 1961 into two categories; those predominantly continuous and those predominantly showery precipitation, using both constant altitude radar pictures and hourly precipitation records. There was a slight tendency for the higher tritium concentrations to occur in continuous precipitation. Height/time diagrams showing the positions of the various airmasses over Ottawa revealed that the highest tritium concentrations occurred when maritime arctic air extended from the ground to the tropopause. On occasions with mA air at the ground and other airmasses above it, the measured tritium concentration was approximately proportional to the depth of mA air traversed by the precipitation. The lowest tritium concentration was measured in a storm wholly contained in mT air. Air mass trajectories confirmed that the higher concentrations were measured in precipitation which had fallen through air of arctic origin with an arctic trajectory than through air of tropical origin.

Experimental evidence is presented in support of the hypothesis that real, large-scale divergence and energy conversion processes can be analysed from the winds and temperatures reported by the present North American rawinsonde network. The Bellamy triangle method has been used to produce divergence and this divergence is shown to have continuity in the horizontal, the vertical and in time. A discussion of the scale on which this parameter can be analysed objectively and the errors involved are presented. Energy conversion processes associated with an individual weather system are displayed in map form for comparison with other synoptic features.

This study considers the geographical distribution of total ozone through its correlation with various meteorological parameters. In particular, the seasonal and latitudinal variations of these correlations are examined. The relationships obtained are then used to prepare maps of total ozone distribution on a daily basis for each fifth day for the period October 1958 to March 1959, and for each tenth day for the period April 1959 to September 1959. The results provide an improved description of the behaviour and distribution of total ozone on a hemispheric scale.

The study recorded here was undertaken as a contribution to a larger study involving the heat balance of the Arctic. The purpose of the study was to investigate the nature of atmospheric systems which bring about the poleward heat transport at these latitudes as well as the magnitude of the total transport. At the same time the possibility of relating the heat transport to the circulation pattern was studied. The period of study was January, February and December, 1958 and 1959. Special attention was given to two six day periods in January, 1958.