URBAN EVAPOTRANSPIRATION IN WATER SCARCE REGIONS ESTIMATES FOR THE MIDDLE RIO GRANDE BASIN, UNITED STATES AND MEXICO

Urban evapotranspiration (ET) in semi-arid and arid regions is an important component of the urban water cycle, especially in regions that have limited freshwater supplies. Understanding urban evapotranspiration in these regions is necessary for assessing and managing water resources and ensuring that conservation strategies are effective and sustainable. The objective of this study is to estimate urban ET in the Middle Rio Grande Basin to provide an understanding of evaporative water losses in semi-arid to arid urban environments for future water management decisions. The focus of this study is on the cities of El Paso, TX, US; Las Cruces, NM, US; and Ciudad Juarez, CH, MX. Components of urban ET include vegetation and bare soil ET, open water evaporation, evaporation from infrastructure losses, and evaporative cooler evaporation. Multiple methods were used to provide an estimate of total urban ET from individual components, as well as total ET for each city at an average annual time scale. Average urban ET for the study area, including evaporation from precipitation, is approximately 500 mm annually. Urban ET accounts for up to 60% of annual water demand and ranges from an average of 13 million m3 annually in Las Cruces to 91 million m3 annually in El Paso. Water conservation and management is crucial in water scarce environments, especially as urban populations increase and freshwater supplies continue to decrease in many regions along with shifts in climate. Water loss to ET is an important component of the urban water cycle and must be considered in conservation and management decisions for urban water supplies to remain sustainable in the future

Kaleidoscope of Urban Evapotranspiration: Exploring the Science and Modeling Approaches

Urban evapotranspiration is a complex physical process. It depends on various critical drivers, including the land surface temperature (LST), surface albedo, landscape types, and building orientations. All of these factors create difficulties in the estimation of evapotranspiration (ET) by changing the microclimate conditions. The literature has oversimplified microclimate conditions by considering temperature difference as the only variable defining climate. The physical process depends on land-use changes, building proximities, and landscape types. This study devised three objectives to understand the microclimate effects on ET. In the first objective, land-use change effects on LST, surface albedo, and ET were analyzed over a period of twenty-seven years in the Las Vegas Valley. The analysis employed trends and shifts using Mann Kendal\u27s test and Pettit\u27s test, respectively. Land use encompassed four prominent urban surfaces, including residential, commercial, asphalt, and turf grass surfaces. The commercial and asphalt surfaces proved to be the main contributors to increased LST and decreased surface albedo. However, the increase in LST was lower than the rural surface increase, illustrating overall cooling in the summertime due to development. The removal of turf grass over the study period showed a significant increase in LST, while turf grass development showed an overall increase in ET. This study can help water managers and urban planners to understand the role of land-use change in irrigation water demand and urban thermal comfort. This study has been submitted to the Urban Climate Journal. The second objective was devised to understand the surface energy budget due to the presence and proximity of buildings. The study analyzed net radiation and soil heat flux, as well as the surface temperatures of canyons, rooftops, and turf grass, to understand day-time and nighttime warming. A 68 sq. km parcel in Phoenix, AZ was studied for the analysis. The findings suggest that canyons\u27 land surface temperatures (LST) were lower than rooftop surfaces, while turf grass surfaces were cooler than canyon surfaces. Moreover, north and south (N-S) oriented canyons were cooler than east and west (E-W) oriented canyons. No significant changes were observed in the net radiation for rooftop, turf grass, and canyon surfaces. However, the soil heat flux, warranting nighttime warming, showed higher absorption on rooftop surfaces than in canyons. The turf grass reported nighttime cooling, as the heat absorption was lower than the rooftop surfaces and the canyons. Additionally, a significant difference in heat absorption was observed between N-S oriented canyons and E-W oriented canyons. The study concluded that canyons and their orientations are major causes of daytime cooling and nighttime warming. For Phoenix, the N-S oriented streets are cooler than the E-W oriented streets. This study recommends studying canyons\u27 local municipalities, and developing a master plan for cities\u27 construction accordingly. This study has been submitted to the International Journal of Remote Sensing. The third objective investigated the microclimate effects and irrigation water requirements of three landscape types in an arid region of Phoenix, AZ. The microclimate effect encompassed surface temperature, air temperature, and wind speed. The three landscapes include mesic, oasis, and xeric. The simulation was conducted using ENVI-met software for the hottest day of the year (23rd June 2011). The simulated model was validated using ground data. The results showed that the mesic landscape induced cooling effects, both in the day-time and nighttime, by reducing the surface temperature, air temperature, and wind speed. However, the mesic landscape showed high-water consumption because of high leaf area density. The oasis landscape showed more day-time cooling than the mesic landscape, but the nighttime warming was like a xeric landscape. However, the potential irrigation water requirement was lower than the mesic landscape. Moreover, the surfaces between buildings showed varying microclimate conditions. In the case of mesic landscape, the surfaces showed high wind speeds and higher temperatures. The xeric landscape showed lower wind speeds and air temperatures between the buildings. Overall, the oasis landscape proved to be the most efficient of the three landscapes for water consumption and day-time cooling. This study will be submitted to the Journal of Advances in Modeling Earth Systems (JAMES), AGU. To sum up, both surface properties (land use) and orientation (canyons) affect the surface energy budget. Landscape type also contributes to air temperature and surface temperature changes, while air temperature changes related to wind speed. Changes in the surface energy budget affect ET rates in arid regions (Las Vegas Valley and Phoenix)

Impact of land use change on urban surface temperature and urban green space planning; case study of the island of Bali, Indonesia

Land use and surface temperature were monitored from 1995 to 2013 to examine green space development in Bali using Landsat and ASTER imageries. Urban areas were formed by conversion of vegetation and paddy fields. Heat islands with surface temperature of over 29 ºC were found and influenced by urban area types. High priority, low priority and not a priority zones for green space were resulted by weighted overlay of LST, NDVI and urban area types

An overview of monitoring methods for assessing the performance of nature-based solutions against natural hazards

To bring to fruition the capability of nature-based solutions (NBS) in mitigating hydro-meteorological risks (HMRs) and facilitate their widespread uptake require a consolidated knowledge-base related to their monitoring methods, efficiency, functioning and the ecosystem services they provide. We attempt to fill this knowledge gap by reviewing and compiling the existing scientific literature on methods, including ground-based measurements (e.g. gauging stations, wireless sensor network) and remote sensing observations (e.g. from topographic LiDAR, multispectral and radar sensors) that have been used and/or can be relevant to monitor the performance of NBS against five HMRs: floods, droughts, heatwaves, landslides, and storm surges and coastal erosion. These can allow the mapping of the risks and impacts of the specific hydro-meteorological events. We found that the selection and application of monitoring methods mostly rely on the particular NBS being monitored, resource availability (e.g. time, budget, space) and type of HMRs. No standalone method currently exists that can allow monitoring the performance of NBS in its broadest view. However, equipments, tools and technologies developed for other purposes, such as for ground-based measurements and atmospheric observations, can be applied to accurately monitor the performance of NBS to mitigate HMRs. We also focused on the capabilities of passive and active remote sensing, pointing out their associated opportunities and difficulties for NBS monitoring application. We conclude that the advancement in airborne and satellite-based remote sensing technology has signified a leap in the systematic monitoring of NBS performance, as well as provided a robust way for the spatial and temporal comparison of NBS intervention versus its absence. This improved performance measurement can support the evaluation of existing uncertainty and scepticism in selecting NBS over the artificially built concrete structures or grey approaches by addressing the questions of performance precariousness. Remote sensing technical developments, however, take time to shift toward a state of operational readiness for monitoring the progress of NBS in place (e.g. green NBS growth rate, their changes and effectiveness through time). More research is required to develop a holistic approach, which could routinely and continually monitor the performance of NBS over a large scale of intervention. This performance evaluation could increase the ecological and socio-economic benefits of NBS, and also create high levels of their acceptance and confidence by overcoming potential scepticism of NBS implementations

Progress in urban greenery mitigation science – assessment methodologies advanced technologies and impact on cities

Urban greenery is a natural solution to cool cities and provide comfort, clean air and significant social, health and economic benefits. This paper aims to present the latest progress on the field of greenery urban mitigation techniques including aspects related to the theoretical and experimental assessment of the greenery cooling potential, the impact on urban vegetation on energy, health and comfort and the acquired knowledge on the best integration of the various types of greenery in the urban frame. Also to present the recent knowledge on the impact of climate change on the cooling performance of urban vegetation and investigate and analyse possible technological solutions to face the impact of high ambient temperatures

Climate and more sustainable cities: climate information for improved planning and management of cities (producers/capabilities perspective)

In the last two decades substantial advances have been made in the understanding of the scientific basis of urban climates. These are reviewed here with attention to sustainability of cities, applications that use climate information, and scientific understanding in relation to measurements and modelling. Consideration is given from street (micro) scale to neighbourhood (local) to city and region (meso) scale. Those areas where improvements are needed in the next decade to ensure more sustainable cities are identified. High-priority recommendations are made in the following six strategic areas: observations, data, understanding, modelling, tools and education. These include the need for more operational urban measurement stations and networks; for an international data archive to aid translation of research findings into design tools, along with guidelines for different climate zones and land uses; to develop methods to analyse atmospheric data measured above complex urban surfaces; to improve short-range, high-resolution numerical prediction of weather, air quality and chemical dispersion through improved modelling of the biogeophysical features of the urban land surface; to improve education about urban meteorology; and to encourage communication across scientific disciplines at a range of spatial and temporal scales

Urban heat mitigation in Sydney, Australia : tree effects and policy context

Rapid urbanization, land use modification and anthropogenic heat emission have accelerated the Urban Heat Island Effect (UHIE) in cities. The UHIE can be defined as the “discernible temperature difference between urban and adjacent rural areas caused by the excess heat emitted and the solar gain trapped by the urbanised environment” (Gartland, 2008). Trees provide cooling through evapotranspiration and surface shading. This thesis takes a transdisciplinary approach to assess the efficacy of trees in cooling urban spaces in Sydney and how well this function is embedded in government policies. Overall, this research showed that both science and policy play a key role in the pathway to achieve urban cooling. Effective urban heat management must be guided by comprehensive urban planning policies. Therefore, the key planning policies of local and state government agencies should contain a standalone provision for urban heat management. While there are numerous scientific studies conducted in Australia on UHIE, their integration within strategic planning at local and state government levels is currently inadequate. Surprisingly, none of the councils examined in the study had firm canopy cover targets associated with expected cooling benefits. This indicates that policy makers at all government levels need to have a deeper understanding about urban heat and how to reduce it or adapt to it. This research provides new strategic guidance to better understand spatial and temporal variability of urban heat and offers improvements to existing practices for planting and managing urban trees

Nature in Megacities: São Paulo/Brazil - A Case Study

Die vorliegende Studie analysiert Umweltdienstleistungen von städtischer Vegetation innerhalb der Stadtgrenzen einer Megacity durch maßstabsübergreifende Modellierung und versucht ihren Nutzen näherungsweise zu quantifizieren. Aus verschiedenen Blickwinkeln werden die Vorteile (sowie die Herausforderungen) von in Städte eingebetteter Natur für die Bevölkerung aufgezeigt. Aus geographischer Sicht wird, hier am Fallbeispiel der Stadt São Paulo/ Brasilien, das Profil der Megastädte in den niedrigen (tropischen) Breiten betrachtet. Im allgemeinen wird die städtische Vegetation dort von Bevölkerung, Regierungen und ökonomischen Strukturen vernachlässigt. Sie ist zwar spärlich vorhanden, wird aber kaum bewusst wahrgenommen.Während der kurzen Geschichte rasanter Verstädterung, die von massiver Umweltzerstörung begleitet ist, wird Stadtgrün im Disput um den Raum in Städten wie São Paulo zum wahren Luxus. Nicht als Rückentwicklung, sondern als Fortschritt, wird gezeigt, daß ein Ideal durch die Verflechtung zwischen Natur und Stadt dargestellt würde. Die näherungsweise Quantifizierung der Variationen zwischen aktuellem Szenario und begrünten Szenarien zeigt die Notwendigkeit das städtische Biom als ein vom Menschen dominiertes Ökosystem neu zu überdenken. Die Nutzen von städtischer Vegetation sind facettenreich. Diese Arbeit detailliert Vegetation als Katalysator des klimatischen und ökologischen Gleichgewichtes. Des weiteren behandlt sie aktuelle Themen wie Klimawandel, Energieeffizienz und thermische Behaglichkeit, sowie die Reinigung der natürlichen Ressourcen Boden, Wasser und Luft. Insbesondere da derzeit keine effizienten technischen Lösungen existieren, um die Umweltleistungen der Vegetation zu ersetzten. Diese Nutzen tragen zur Lebensqualität und in kontrastreichen Megastädten insbesondere zu sozio-ökologischer Gerechtigkeit bei. Die Vegetation hat in Städten zwei wichtige Dimensionen. Die funktionale Seite bringt konkrete, meßbare Umweltnutzen. Aus symbolischer Sicht repräsentiert Vegetation Natur in Städten, sowie ursprüngliche Naturverbundenheit des Menschen. Zusammenfassend verteidigt die Studie die Wichtigkeit und Wertschätzung von Natur und die vereinigten Anstrengung für wirklich grüne Städte, u.a. weil diese Arbeit zeigt, dass finanzielle Investitionen in städtische Vegetation sich direkt auf die Kosten für das Gesundheitssystem und die Infrastruktur auswirken. Die Stadtregierung São Paulo investierte 2008 umgerechnet 122 Millionen Euro (einhundertzweiundzwanzig Millionen Euro) in Stadtgrün (und Umwelt), dass jährlich mindestens 665 Millionen Euro (Sechshunderfünfundsechzig Millionen Euro) einspart. D.h. mit anderen Worten, dass jeder Euro 1 der in Pflanzung und Pflege von Stadtgrün investiert wird, der Gesellschaft, und damit letzendlich den Einwohnern São Paulos, Ausgaben von mindestens 5 Euro für Gesundheit, den Bau von Regenwasserrückhaltebecken, Energie etc. einspart.The present study analysis the environmental benefits of urban vegetation within the municipal boundary of a megacity through multi scale integrated modelling to estimate its benefits approximately. The advantages (and challenges) that Nature, inserted into cities, offers to the population are observed from different viewpoints. As geographical reference the profile of megacities located in low (tropical) latitudes was observed, in a case study on the city of São Paulo/ Brazil. Commonly, urban vegetation is overlooked by local people, governments and economical structures. Although sparse vegetation exists, it is hardly recognized. Along the brief history of rapid urbanization which is accompanied by massive environmental degradation, urban green becomes, in the dispute for space, a true luxury in cities like São Paulo. Not as retrogression but as advance, it demonstrates that the integration between nature and city would be desirable. The approximated quantification of the variations which occur between actual scenario and greened scenarios shows the need to rethink the urban biome as a man-dominated ecosystem. The benefits of the urban vegetation are diverse. This work details plants as agents of climatic and ecosystem balance and performance. It also approaches current issues like climate change, energy efficiency and thermal comfort, as well as the purification of natural resources, through the treatment of water, soil and air. Especially because at present no efficient technical solutions exist, that could substitute the environmental services of the vegetation. These benefits contribute to quality of life and increase socio-environmental equity especially important in high-contrast megacities. The vegetation assumes two important roles in cities. The functional dimension brings concrete and measurable benefits to the environment. From a symbolic vision, vegetation represents Nature in cities, approximating humans to their origins. Conclusively the study defends the importance of the valorization of Nature and of the united efforts for literally green cities because it proves that financial investment in urban vegetation has direct effects on the costs destined to the areas of health and infrastructure. The City of São Paulo, invested in 2008 about US$180 million (one hundred and eighty million dollars) in urban green (and environment) which tends to save US$ 980 million (nine hundred and eighty million dollars) of expenses annually. In other words, for each US$1 invested in planting and maintenance of urban green, the society saves at least US$ 5 of expenses in health, construction of French drains, energy etc

Spatial patterning in albedo and biogenic carbon exchange in urban areas

Urbanization alters surface energy and biogenic carbon (C) exchange processes which can exacerbate increases in near-surface temperature and complicate municipal-scale efforts to address the local causes and impacts of climate change. This dissertation integrates field- and remote-sensing datasets to evaluate the magnitude of and spatial patterns in albedo and biogenic C fluxes in the urban landscape, focusing on the region of Greater Boston, Massachusetts. Using surface reflectance measurements from the Landsat and MODIS satellites, we show mean albedo in the Boston metropolitan region was significantly lower in core population centers than nearby rural areas, corresponding to reduced tree cover, greater impervious surface area, and higher surface temperatures. These results establish albedo decline as a gradient in landscape-scale features of urbanization, and offer context for efforts to mitigate extreme urban temperatures through raising the albedo of built surfaces. Pairing field measurements of tree growth with LiDAR-based data on tree biomass and canopy cover, we estimate the distribution of annual woody biomass C uptake in the city of Boston. A substantial portion of tree C uptake occurred in densely developed residential areas dominated by open-grown trees as well as remnant forest fragments. Our results show that estimates based on rural tree growth may under-predict C uptake by up to approximately 50%, and quantifies the scope for policy interventions aimed toward increasing ecosystem services output from the urban forest. Fusing measurements of soil respiration and net vegetation productivity in lawns and trees with high-resolution land surface data, we develop an improved estimate of annual biogenic net carbon fluxes in Boston at a 30 m resolution. We find forested areas of the city may be a modest net sink for C (median 2.7 GgC yr-1), but also estimate substantial C flux from intensively managed landscapes in residential areas. Estimated city-wide biogenic C was relatively small (median 600 MgC yr-1), potentially offsetting less than 1% of estimated annual fossil fuel emissions. Our results imply net biogenic C flux likely will contribute little towards efforts to reduce local net greenhouse gas emissions, but may significantly influence urban atmospheric CO2 concentrations at certain times and places

EFFECT OF ROOFTOP GREENERY ON OUTDOOR MEAN RADIANT TEMPERATURE IN THE TROPICAL URBAN ENVIRONMENT

Ph.DDOCTOR OF PHILOSOPH