Clouds strongly influence three-dimensional aerosol distributions by 1) wet scavenging and subsequent deposition to the earth's surface, and 2) processing and subsequent release to the atmosphere by evaporation processes. In this study, physically detailed size-dependent representations of below-cloud and in-cloud scavenging for mixed phase clouds are introduced into the ECHAM5-HAM global climate model. As well, a stratiform cloud aerosol processing scheme is extended to convective clouds. Below-cloud impaction scavenging is found to contribute strongly to the global and annual mean mass deposition for sulfate (14%), black carbon (13%), particulate organic matter (10%), sea salt (23%), and dust (24%). The modeled global mean aerosol optical depth, and sea salt burden are reduced by about 15% for the more vigorous size-dependent parameterization of below-cloud scavenging by rain and snow. In stratiform clouds, aerosol mass is found to be primarily (>90%) scavenged by cloud nucleation processes for all aerosol species, except for dust (50%). Uncertainties in the representation of in-cloud scavenging processes change the predicted annual, global mean aerosol mass burdens by 20 to 30%, and change the predicted aerosol mass concentrations by up to one order of magnitude in the middle troposphere where mixed phase clouds exist. Closer agreement with observations of black carbon profiles from aircraft is found for the new in-cloud scavenging scheme. Convective and stratiform clouds contribute about equally to the global, annual mean aerosol processing, but wet deposition is primarily attributed to stratiform clouds (75%). Sulfate and carbonaceous aerosols undergo 1-3 cloud cycles before deposition. Aerosol burdens and optical depth (AOD) increase by a factor of 3-5 with the explicit representation of cloud/precipitation evaporation. Revised sea salt emissions and more vigorous in-cloud impaction scavenging reduce the AOD by a factor of three to give closer agreement with satellite retrievals. Observed marine boundary layer accumulation mode size distributions, and vertically integrated aerosol size distributions from AERONET observations are more closely approximated with the aerosol processing scheme than for the standard ECHAM5-HAM.

This text/video thesis investigates how Canadian fathers feel about the threat of losing pond hockey, a revered game they love, to climate change. It responds to the David Suzuki Foundation’s (DSF) assertion that under a global ‘business as usual’ rate of producing greenhouse gases, the skating season of the world’s largest ‘rink’--the Rideau Canal--would shrink from a nine week historical average to just one week by century’s end (DSF, 2009a). Seven outdoor-hockey-loving fathers were interviewed, which revealed their willingness to share feelings of concern, sadness, fear, uncertainty, and need for action to mitigate against and adapt to the ill-effects of climate change on this game, and more serious social situations. Despite concerns it was revealed they took few substantial actions against climate change, which they recognized might affect themselves, their children, communities, and future generations. Conversation, at times nostalgic, helped make these issues more salient.

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The studies in this dissertation aim at advancing our scientific understandings about physical processes involved in the aerosol-cloud-precipitation interaction and quantitatively assessing the impacts of aerosols on the cloud systems with diverse scales over the globe on the basis of the observational data analysis and various modeling studies. Long-term impacts of aerosols on precipitation and lightning over the Pearl River Delta megacity area in China are identified through the analysis of seven-year measurements of precipitation, lightning flashes, and visibility from 2000 to 2006. The cloud resolving - Weather Research and Forecasting (CR-WRF) model with a two- moment bulk microphysical scheme is employed to simulate a mesoscale convective system in the Guangzhou megacity area and to elucidate the effects of aerosols on cloud processes, precipitation, and lightning activity. The responses of hydrometeors and latent heat release to different aerosol loadings reveal the physical mechanism for the precipitation and lightning enhancement in the Guangzhou megacity area, showing more efficient mixed phase processes and intensified convection under the polluted aerosol condition. Sensitivity modeling experiments are performed for maritime warm stratocumulus clouds over the southeast Pacific Ocean to evaluate the microphysical parameterizations for simulations of the aerosol effects in regional and global climate models. The Morrison double-moment bulk microphysical scheme presently implemented in the WRF model is modified by replacing the fixed aerosols in the original bulk scheme with a prognostic double-moment aerosol representation to predict both aerosol number concentration and mass mixing ratio. The impacts of the parameterizations of diffusional growth and autoconversion of cloud droplets and the selection of the embryonic raindrop radius on the performance of the bulk microphysical scheme are also evaluated. The impacts of Asian pollution outflows on the Pacific storm track are assessed utilizing reanalysis data, a hierarchical modeling approach and the multi-scale aerosol- climate modeling frame. Statistical analysis of two sets of reanalysis data suggests a strengthened trend of the storm track intensity over the North Pacific since 1979. The two-month seasonal simulations using a CR-WRF model with a two-moment bulk microphysics are performed to examine the aerosol effects on the Pacific storm track intensity. Subsequently, the anomalies of the diabatic heating rate by the Asian pollution outflow derived from the CR-WRF simulations have been prescribed in the NACR Community Atmosphere Model (CAM5) to provide the aerosol forcing terms. The forced GCM well reproduces an enhancement in the intensity of storm track, compared to the unforced model simulations. Similarly, under the multi-scale aerosol-climate modeling frame, the comparisons of the simulated present day versus pre-industrial climate corresponding to two different aerosol scenarios indicate the increased precipitation and poleward heat transport for the present-day climate reveal invigorated mid-latitude cyclones. The current work illustrates the complexity of the aerosol effects on the cloud systems at the diverse scales with different meteorological conditions. This study also stresses the importance of accurate representation of aerosol forcings in the different types of atmospheric numerical models for future climate projections.

Suspended sediment delivery dynamics in two watersheds at Cape Bounty, Melville Island, Nunavut, Canada were studied to characterize the hydroclimate conditions in which laminated sediments formed. Process work over three years determined snow-water equivalence was the primary factor that controlled sediment yield in both catchments. Cool springs (2003, 2004) enhanced runoff potential and intensity because channelized meltwater was delayed as it tunneled through the snowpack and reached the river channel (sediment supply) within 1-2 days. In warm springs (2005), meltwater channelized on the snowpack and did not immediately reach the river bed (7-10 days). Sediment transport was reduced because flow competence was lower and sediment supplies limited. Sediment deposition in the West Lake depended on surface runoff intensity. Short-lived, intense episodes of turbid inflow generated underflow activity which delivered the majority of seasonal sediment. In 2005, runoff was less intense and few underflows were detected compared to the cooler, underflow dominated 2004 runoff season. As well, grain-size analysis of trapped sediment indicated that deposition rates and maximum grain-size were decoupled, indicative of varied sediment supplies and delivery within the fluvial system. These decoupled conditions have important implications for paleohydrological interpretations from downstream sedimentary records. Two similar 600-year varve records were constructed from the lakes at Cape Bounty. Although these series were highly correlated throughout, time-dependent correlation analysis identified divergence in the early 19th century. Because the varve records were from adjacent watersheds and subject to the same hydroclimatic conditions, the divergence suggests watershed-level changes, such as increased local active layer detachments. The varve record from West Lake was highly correlated with lagged autumn snowfall and spring temperature. Similar relationships between these variables and East Lake were not as strong or significant. Long-term climatic interpretations should be carefully assessed. A single record from either of these lakes might lead to autumn snowfall and/or spring-melt intensity reconstructions, given the process work and weather record correlations. The recent divergence reveals potential changes likely to occur as warming increases variability within the Arctic System. Multidisciplinary monitoring and observations should continue in order to quantify future variability and evaluate the impact on these systems. / Thesis (Ph.D, Geography) -- Queen's University, 2008-09-02 12:11:53.483

Clastic varves and tree-rings offer unique opportunities to decipher various changing paleoclimatic and environmental conditions through the past. The environmental signals they contain can differ greatly from one proxy to the other, but given their common annual resolution, these signals can be isolated, compared and eventually brought together to obtain a clearer picture of local, regional or global environmental changes. This thesis examines three different approaches by which climatic, paleoclimatic and sedimentary time series from northeastern North America can be used as proxies of changing environmental conditions. Using existing and new paleoclimatic records from the eastern Canadian Boreal biome and the Arctic, we show that common variance shared by different independent proxies appears to correspond to an oscillation in North Atlantic sea surface temperatures commonly referred as the Atlantic Multidecadal Oscillation (AMO) and demonstrate that the AMO can be traced back to 1550 in the Canadian Arctic. By comparing historical climate records with an integrated record of North Atlantic sea surface temperature anomalies, we show, seasonally, the extent of the North Atlantic influence on the eastern and Arctic climate. Our analysis demonstrate the relative importance of the AMO on summer and spring climate in northern Canada as well as its imprint along the St. Lawrence during the winter months. Finally at the local level, using an array of techniques, we investigate the sedimentary history of Temiskaming Lake (Québec/Canada). The recent clastic varve sediments found this lake appear to be the product of three main controls: (1) a significant increase in fluvial input to the lake and accessibility to large supply of fine grained sediments due to historical land use changes; (2) an open, unstable landscape that promotes fluvial erosion and rapid streamflow during snowmelt period; and, (3) highly seasonal river discharge and presence of winter ice cover conditions that ensure the formation of annual structures within the sediments. These conditions have previously not been investigated or reported in the boreal region of North America and these results point to the potential for other recent varve records in areas with suitable lakes and postglacial sediment supplies. / Thesis (Ph.D, Geography) -- Queen's University, 2008-12-18 12:22:27.663

The study of long-term climatic change in the Arctic, a region both particularly sensitive to the effects of a warming climate and an important driver of global climate, is pertinent to understanding the rates and magnitude of current ecosystem changes. Analyses on geological time frames provide insight into the variability of Arctic climate, allowing a contextualized understanding of recent ecosystem changes that have been documented across the Arctic. Lake CF8, a mid-Arctic lake on Clyde Foreland, Baffin Island, contains a unique sedimentary archive of the present and last two interglacial periods, due to past non-erosive glaciation patterns, providing an opportunity to study interglacial climate trends. Diatom assemblages were analyzed through the organic sediment record of the past three interglacials. Trends in the ontogeny of this lake were revealed: the early, post-glacial environment was dominated by species of the colonial Fragilaria genera, which transitioned into high relative abundances of tychoplanktonic Aulacoseira species. Benthic/periphytic taxa, such as Psammothidium marginulatum, tended to increase in relative abundance in the mid- to late-interglacial periods. The ecological interpretation of this pattern is examined in this study, and suggests that climate drives the succession of the diatom community primarily through indirect effects on lake ice and pH. The extent of ice cover likely plays a large role in the biotic community of this lake; the diatom assemblages within the past ~ 50 years indicate increasing littoral habitat complexity with a peak in Eunotia species and a slightly acidic pH, which is discussed in relation to changing habitat availability associated with decreasing ice cover. In-lake production was examined through the use of spectrally-inferred chlorophyll a trends, which also indicate elevated production in the past ~ 50 years. As climate change becomes an increasingly significant threat to the stability of Arctic ecosystems, interest in paleoclimate records that extend into past, non-anthropogenically mediated warm periods, is increasing. This sediment record extends our understanding of past environmental trends beyond the longest records in this part of the Arctic, the Greenland ice core records, and enhances our understanding of the variability of Arctic climate. / Thesis (Master, Biology) -- Queen's University, 2009-05-06 17:04:38.302

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Determining optimum building orientation for naturally ventilated buildings is an important concept. Obtaining the optimum orientation will determine the success of the performance of a naturally ventilated building. / This project deals with obtaining the preferred building orientation for 10 regional weather stations across the province of Ontario. Different methods were utilized to obtain the preferred building orientation: the average ventilation rate method, the percentage of ventilation rates above and below the minimum summer ventilation rates, and the consecutive hours method, ie. the number of weather events that are below the minimum summer design ventilation rate for a specific building configuration. The analysis involves six building orientations (0$ sp circ$, 30$ sp circ$, 60$ sp circ$, 90$ sp circ$, 120$ sp circ$, and 150$ sp circ$) with respect to North, and exterior temperatures greater than or equal to 20$ sp circ$C, 25$ sp circ$C, or 30$ sp circ$C. / Optimizing building orientation, to minimize the number of weather events where the ventilation rates are below the summer design ventilation rate is the general goal of this research work. / A statistical analysis was carried out based on the results obtained from the data for the frequency of ventilation rates versus the ventilation rates below the summer design ventilation rate, for all 10 Ontario weather stations, for temperatures greater than or equal to 20$ sp circ$C, and all six building orientations. The output of the statistical analysis showed that for the above mentioned temperature range, that there is a relationship between the ventilation rates below the design summer ventilation rate and building orientation.