The process of urbanization dramatically alters the landscape which can have negative effects on the environment, and thereby, places the inhabitants and the city itself at risk. The development of an urban heat island can have severe health implications for city inhabitants during prolonged heat waves. Urbanisation also alters hydrological processes, which can place urban areas at a greater threat of surface flooding during heavy rainfall. As cities are continuing to expand, and as climate change proceeds, these problems are only likely to be exacerbated and there is a need to find ways to reduce these negative effects.This thesis builds upon previous modelling work on the effect of greenspace on the climate and hydrology of Manchester, U.K. The aims were to test the predictions of this model by investigating the effect of trees and grass in reducing surface temperatures and rainfall runoff, and further investigate their effects on air and globe temperatures. Surface, globe, and air temperatures were measured on grass and concrete areas in full sun and tree shade, both under large tree canopies, and below those of a range of street tree species. The rainfall runoff from experimental plots covered in asphalt, asphalt plus a tree and grass, was also investigated. Grass reduced surface temperatures in full sun by up to 24°C, in good agreement with previous models, but permanent tree shade reduced concrete temperatures by almost as much, up to 19°C. Tree shade also reduced globe temperatures by up to 7°C, a reduction which can improve human comfort on hot day. These results indicate that both forms of vegetation will act regionally, reducing the urban heat island effect, but that trees can dramatically improve the local environmental conditions. Street trees reduced surface and globe temperatures by rather less, 12°C and 4°C respectively, though trees with a higher leaf area index provided greater cooling. Because of advection neither trees nor small areas of grass had an effect on local air temperatures.Grass was most effective vegetation type at preventing rainfall runoff, reducing runoff coefficients of the plots from around 60% on asphalt to near zero. However, tree units also reduced the runoff coefficient to around 25%, despite having a canopy that covered only a small proportion of the plot, suggesting that much of the rainfall must have infiltrated into the planting hole. These reductions are higher than predicted by previous modelling, highlighting the importance of greenspace on the hydrology of the urban environment.The results suggest that trees and grass provide complementary environmental benefits in cities, and that the benefits of trees strongly depend on species and planting conditions

The urban heat island (UHI) is a problem that is likely to be exacerbated by ongoing climate change, but it is often claimed that urban trees can mitigate it and hence adapt our cities to climate change. Many researchers have attempted to quantify the cooling effects of trees using modelling approaches. However, the major disadvantage of most of the models is that they consider all vegetation to act as a single saturated layer and that their effect is merely proportional to its surface cover. Therefore, they fail to take into account potential differences between tree species and the effect of different environmental and growing conditions. To address this issue four different studies were conducted in Manchester, UK from February, 2010 to December, 2012. The studies compared the growth and cooling abilities of several commonly planted urban tree species, and investigated a single species planted in a range of growing conditions: investigating the effect of urban soil compaction and aeration and also the effect of urbanization and simulated climate change in the rooting zone. Overall, our studies showed that species selection and growing conditions can substantially alter the evapotranspirational cooling provided by urban trees. Fast growing species such as Pyrus calleryana, with their dense and wide canopy can provide cooling up to 2.2 kW tree-1, 3-4 times that of Sorbus arnoldiana, which have a thinner and narrower canopy and a moderate growth rate. P. calleryana was also investigated under three contrasting growth conditions: in cut-out pits in pavements; in grass verges; and in pits filled with Amsterdam soil. Trees in the less compacted Amsterdam soil had grown almost twice as fast as those in pavements and also had better leaf physiological performance. Together with a longer growing season, and better uptake of soil nutrients and moisture, trees grown in Amsterdam soil provided evapotranspirational cooling of up to 7kW, 5 times higher than those grown in pavements. Another experiment in which P. calleryana trees were planted in 3 standard planting techniques with non-compacted load bearing soils and with or without permeable slabs showed that optimum cooling is not only dependent on preventing soil compaction but also on ensuring that the covering materials are permeable to oxygen. Trees in the open pits provided up-to 1 kW of cooling, compared to around 350 and 650 W by the small and large covered pits respectively. Our final experiment showed that urbanization can increase tree growth by 20-30%; however, despite being under more water stressed conditions trees grown in simulated climate change plots had 40% higher sap flux density, and hence cooling potential. The study suggested that at least with P. calleryana, transpirational cooling benefit might be enhanced in places like Manchester with increased soil temperature in future, but potentially at the expense of photosynthesis and carbon gain. Together these studies show that evaporative cooling of trees depends strongly on both species and growing conditions. If incorporated into regional and local energy exchange models our results can help us to quantify the magnitude and effectiveness of greenspaces in the city in adapting them to climate change.

Urban populations worldwide are expanding rapidly and consequently a large number of people are becoming exposed to hazards inherent in cites. Phenomena such as the urban heat island can exacerbate the effects of heatwaves, and land surface sealing can lead to flash flooding. Cities are also the sites of enhanced air and water pollution from non-point sources such as concentrated motor vehicle use. Climate change predictions for the UK include increased winter precipitation and an increase in frequency of summer heatwaves. This will put further pressure on urban residents and infrastructure. Roof greening can be used within climate change adaptation schemes because green roofs have a range of environmental benefits which can help urban infrastructure become more sustainable. This thesis empirically quantifies several of these benefits, and the processes influencing them, by monitoring real green roofs in Manchester. A number of novel discoveries were made. Green roofs act as passive filters of airborne particulate matter. 0.21 tonnes of PM10 (2.3% of the inputs) could be removed from Manchester city centre in a maximum extensive green roof scenario. Species and site differences in particle capture were exhibited and related to morphology and proximity to sources respectively. An intensive green roof was able to lower the monthly median overlying air temperature at 300 mm by up to 1.06 oC. A combination of drought and mismanagement caused damage to the vegetation on one of the green roofs, with a subsequent reduction in the cooling effect. Daytime air temperatures were higher than over an adjacent bare roof for a larger proportion of the day than over the undamaged roof, and lower cooling was observed at night. A site-specific methodology was devised to monitor the rainwater runoff from an intensive green roof and an adjacent bare roof. Average runoff retention of 65.7% was observed on the green roof, compared to 33.6% on the bare roof. Season and rainfall amount had significant impacts on retention, however, many other explanatory variables such as Antecedent Dry Weather Period (ADWP) and peak rainfall intensity had no demonstrable, significant impact. Intensive roof construction on 10% of the rooftops in Manchester city centre would increase annual rainfall retention by 2.3%. The runoff was characterised with regards to heavy metals and nutrients. Nutrient levels were found to be not a significant problem for water quality, however, Environmental Quality Standards (EQS) values for protection of freshwater were exceeded for concentrations of Cu, Pb and Zn. High metal concentrations within the sediments may be acting as sources of pollution, particularly in the case of Pb. The age of the green roof means that past atmospheric deposition of Pb could be contributing to the runoff quality. The multi-benefit aspect of green roofs is discussed in the light of the results of this thesis and recommendations made for policy makers and the green roof construction industry.

Meteorological data from two observation sites in Uppsala, the Observatory Park (Op) andthe Geocentre (Gc), during the period January 1998 to September 2000, have been used tocheck the differences in the temperature climate at the two places. Since Op is situatedcloser to the city centre than Gc the site is thought to be more affected by the so calledurban heat island effect. Dependence on different meteorological parameters, time of theday and time of the year, has been investigated and different methods to correct thetemperature for the inhomogeneity that was introduced when the observation site wasmoved from the Observatory Park to the Geocentre. From the different methods investigated it is shown that to correct the temperaturesmeasured at the Geocentre to make them represent the conditions at the Observatory Parka division according to wind speed, wind direction, cloudiness and time of the year wasshown to be the most reliable method. But if it had been possible to divide the material alsointo hours of the day, this would probably have increased the reliability of the correction.For practical purposes a correction simply based on the monthly mean differences betweenthe two sites is probably accurate enough, as the most important factor is the annual cycle inthe temperature difference between the two urban sites. / Väderdata från två observationsplatser i Uppsala, Observatorieparken (Op) och Geocentrum(Gc), under perioden januari 1998 till september 2000, har använts för att undersökaskillnader i temperaturklimatet vid de två platserna. Eftersom Op ligger närmare stadenscentrum än Gc, anses platsen vara mer påverkad av den så kallade värmeöeffekten. Beroendeav olika meteorologiska parametrar, tid på dygnet och tid på året, har undersökts, samt olikametoder att korrigera för inhomogeniteten i temperaturen som introducerades dåobservationsplatsen flyttades från Observatorieparken till Geocentrum. Bland de olika metoder som undersökts för att korrigera de vid Geocentrum uppmättatemperaturerna så att de ska representera förhållandena vid Observatorieparken, visas enuppdelning med avseende på vindhastighet, vindriktning, molnighet och tid på året vara denmest pålitliga metoden, men hade det varit möjligt att dela in materialet även i tid på dygnet,skulle detta troligtvis ha ökat pålitligheten av korrektionen. För praktisk användning är enkorrektion baserad endast på de månatliga medelskillnaderna mellan de två platsernaantagligen tillräcklig, eftersom den viktigaste faktorn är den årliga cykeln itemperaturskillnaden mellan de två platserna.

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Expanding urbanization, characterized by increased impervious surfaces and decreased tree canopy, is contributing to rising urban temperatures. This trend has implications for energy consumption, which strategically placed trees can modify by casting shade upon building and ground surfaces. However, urban densification, a paradigm of modern residential land development, often constrains space for planting shade trees. Thus, the overall objective of this dissertation was to investigate shade tree planting strategies and their effects on residential cooling and heating energy conservation for dense urban neighborhoods in U.S. cities on a latitudinal gradient. The first study used a computer program called Shadow Pattern Simulator to examine the effects of tree form, tree placement, and sunlight exposure on shade provision for a residential structure model. Simulation results affirmed the conventional strategy in northern latitudes that recommends planting shade trees on the east or west aspect for maximizing beneficial shade while avoiding tree plantings on the south aspect to minimize any heating penalty of undesirable shade. However, in southern latitudes, planting trees on southerly aspect should not be discounted because the shorter heating season lessens the detrimental heating penalty while providing beneficial season shade. The second study, using an energy simulation program called EnergyPlus, evaluated the effect of a single shade tree upon the energy consumption of the structure model. This study affirmed that energy conservation benefits are influenced by the quantity as well as the quality of tree shade upon building surfaces. In addition, interactions between sun angle, tree form, and tree placement were observed to influence tree shade effects on annual energy consumption. In the third study, based on the first two studies, an alternative tree placement strategy, which reconfigured tree placement around the residential structure, was developed to maximize cooling and heating energy savings while attenuating space conflicts. The alternative strategy was found to be as effective as the conventional strategy while being more responsive to parcel or building orientations in dense urban neighborhoods. Overall, understanding the fundamental interactions between tree form, tree placement, and geographic settings is critical for improving energy conservation benefits of shade trees in dense urban settings. / Ph. D.

While satellite-based remote sensing techniques are often used for studying and visualizing the urban heat island effect, they are limited in terms of resolution, view bias, and revisit times. In comparison, modern UAVs equipped with infrared sensors allow very fine-scale (cm) data to be collected over smaller areas and can provide the means for a full 3D thermal reconstruction over limited spatial extents. Irrespective of the data collection method, the thermal properties of cities are typically visually represented using color, although the choice of colormap varies widely. Previous cartographic research has demonstrated that colormap and other cartographic choices affect people's understanding. This research study examines the difference in map reading performance between satellite and drone-sourced thermal pseudo-color images for three map reading tasks, the impact of color map selection on map reading, and the potential benefits of adding shading to thermal maps using high-resolution digital surface models for improved interaction. Participants expressed a preference for the newly designed rainbow-style color map "turbo" and the FLIR "ironbow" colormap. However, user preferences were not strongly related to map reading performance, and differences were partly explained by the extra information afforded by multi-hue and shading-enhanced images. / Master of Science / While satellite-based remote sensing techniques are often used for studying and visualizing the urban heat island effect, they are limited in terms of resolution, view bias, and revisit times. In comparison, modern drones or Unmanned Aerial Vehicles (UAVs) equipped with infrared sensors allow very fine-scale (cm) data to be collected over smaller areas and can provide the means for a full 3D thermal reconstruction over a small area. Irrespective of the data collection method, the thermal properties of cities are typically visually represented using color, although the choice of colormap varies widely. Previous cartographic research has demonstrated that colormap and other cartographic choices affect people's understanding. This research study examines the difference in map reading performance between satellite and drone-sourced thermal pseudo-color images for three map reading tasks, the impact of color map selection on map reading, and the potential benefits of adding hillshade augmentation to thermal maps using high-resolution digital surface models for improved interaction. Participants expressed a preference for the newly designed rainbow-style color map "turbo" and the FLIR "ironbow" colormap. However, user preferences were not strongly related to map reading performance, and differences were partly explained by the extra information afforded by multi-hue and shading-enhanced images.