When Weather Matters: Science and Services to Meet Critical Societal Needs (2010)

Grimmond et al. (2009) identified where improvements in Observations, Data, Understanding, Modeling, Tools, and Education are needed to ensure that in the next decade Urban Meteorology supports the development of more sustainable cities. Prioritization is indicated as high (H), medium (M) or low (L). These areas are reproduced below:

• Need operational urban meteorological networks (within and around the city) with optimum balance between resolution and practicability, which include: surface-based instrumentation (soil moisture and air/soil/surface temperature), vertical profiles (from within the deep urban canopy layer to the top of the boundary layer) of temperature, humidity, wind, turbulence, radiation, rainfall, air quality (gases and particles, precursors and secondary), reflectivity and refractivity. (H)

• Need observations over and within a larger range of urban morphologies to establish universal flow and flux characteristics. Need to ensure that there are long term data sets (rather than short term campaigns) that have wide spatial representativeness. The existing long term measurement stations should be preserved. (H)

• Need to measure fluxes of CO₂ using eddy covariance approach combined with isotopic analysis to determine not only the sizes of these fluxes but also to identify emission sources (e.g., background concentration, gasoline combustion, natural gas combustion and respiration) to evaluate the role of cities on the Earth-atmosphere carbon exchange. (H)

• Need to undertake measurement studies to validate quantitative estimates of anthropogenic heat and moisture emissions and improve estimation

techniques at a range of scales starting with the individual building where measurements can close the energy budget on a control volume. (M)

• Need simultaneous measurements of flow properties at various sites and levels to better study coherent structures and intermittent ventilation processes within the roughness sublayer. (M)

• Need to better assess urban surface characteristics (e.g., emissivity to develop methods to correct for thermal anisotropy), and determine fluxes from remote sensing. (M)

• Need to explore the use of new measurement techniques including the use of remote sensing technologies and smaller, more mobile and affordable instruments. (M)

• Need to meet data requirements to allow translation of research findings into urban/building design tools and guidelines for different climate zones and classes of urban land-use. (H)

• Need to ensure that data are provided in a format that is usable for a broad range of practitioners without compromise to scientific accuracy and integrity. (H)

• Need to ensure metadata to describe instrument, siting, quality assurance and control features and documentation are complete and comparable by creating, and using, a standardized urban protocol. (H)

• Need to develop methods and frameworks to analyse atmospheric data measured above complex urban surfaces. This includes measurement source areas to ensure representative results and meaningful comparison between sites. (H)

• Need to know more about the outer layer of the urban boundary layer (UBL), i.e., the atmosphere above the internal surface layer (ISL). (H)

• Need to assess for each intervention what scale interventions are needed and possible (e.g., legally, economically, planning, technically, etc.) to make cities more sustainable (e.g., livable, healthy, etc.). (H)

• Need for assessment of human-induced large-scale climate change at the scale of cities to ensure that the signal of climate change is distinguished from the noise of natural variability. (H)

• Need to better understand the coupling of surface and air temperatures. (M)

• Need to examine ventilation and pollutant removal mechanisms (upward and sideward) for 3D street canyons. (M)

• Need to understand if urban canopies are a special class of rough wall or canopy flows and to what extent urban residual surface layer (RSL) turbulence can be described with a possibly modified mixing layer model. (M)

• Need to increase our knowledge on the subsurface heat island. (L)

• Need to evaluate urban land surface schemes in both offline and online mode for a wide range of conditions to ensure that the models are fit for purpose. (H)

• Need to improve short-range, high-resolution numerical prediction of weather, air quality, and chemical dispersion in the urban zone through improved modeling of the biogeophysical features of the land surface and consequent exchange of heat, moisture, momentum, and radiation (i.e., the surface energy balance, SEB) with the UBL. (H)

• Need CFD/LES studies of wind and pollutant transport studies in regimes other than skimming flow and with combined effects of wind and buoyancy. (H)

• Need to improve understanding of feedback mechanisms between the urban environmental conditions and human activity. (H)

• Need to incorporate more realistic air pollution chemistry mechanisms (e.g., O₃ titration at urban canopy level) into models. (M)

• Need to further develop multi-scale modeling to allow investigations such as: effect of large-scale atmospheric turbulence on the neighborhood- or even micro-scale turbulence below the canopy levels; interaction between natural and artificial landscapes; to assess street-level comfort, building energy consumption and urban design. (M)

• Need laboratory and CFD/LES studies with structures that more closely resemble cities than earlier idealized, homogenous arrays to inform model development for urban RSL turbulence. (M)

• Need further work on a simple universal UHI model for applied users. (L)

• Need to develop tools to allow models to be able to accommodate the wide differences in data availability depending on the application from

research to operational situation e.g., in field research studies, extensive wind observations may be available (and detailed building morphology), but for emergency response situations only minimal inputs may be available (e.g., winds from the nearest airport, no 3-D building data). (H)

• Need to develop designs for hot cities which promote shading and ventilation without compromising air quality and natural lighting. (H)

• Need to encourage development of active simulation tools (e.g. www.susdesign.com/tools.php) through community participation (e.g. forums, blogs, wikis). (H)

• Need to develop tools that allow competing and unintended impacts of proposed sustainable design to be assessed (e.g., will urban greening reduce temperatures but increase humidity, resulting in no net increase in comfort levels?) (H)

• Need to develop tools that allow assessment of the best, or ranking of, social, economic and environmental decisions for urban climate management (e.g., urban greening vs. repaving roads and pavements with high(er) albedo vs. low emissivity materials vs limiting the contribution of anthropogenic heat; investment in expensive multi functional solutions (e.g., vegetated roofs) vs. cheaper, single benefit solutions such as cool roofs). (H)

• Need to make use of spatial and temporal estimation of transport emissions through vehicle fleet efficiencies and traffic data. (M)

• Need to solve technical challenges such as moisture seepage in vegetated roofs, and hazards to street trees (e.g., pests, new pathologies, soil quality, compaction, drainage, frequent disturbances from utility trenches and excessive paving). (M)

• Need to determine how to link the beneficiaries of urban climate interventions with the costs of implementing them. (M)

• Need to ensure widespread education of the meteorological community of the needs for planning and managing cities of all sizes in as sustainable a manner as possible. (H)

• Need to encourage communication which crosses traditional scientific discipline and spatial scales (e.g.: http://www.conservationeconomy.net; http://www.sustainable-buildings.org/index.php). (H)

• Need to improve public education and communication of heat/health perception through use of simple language and community access. (H)

• Need for collaboration with stakeholders in the widespread development of heat/health warning systems. (H)

• Need to communicate through conventional publications and to use current (and evolving) electronic media to allow accessibility with depth of content that is up-to date. (M)

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