Urban Meteorology Forecasting, Monitoring, and Meeting Users' Needs (2012) / Chapter Skim
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3 Science and Technology
3 Science and Technology
Pages 57-92
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3 Science and Technology Various reports have discussed the critical role of urban meteorological observations and forecasting for various aspects of society, such as public health, public safety and security, transportation, water resource management, storm water runoff, and economic development. Although some progress is evident since these reports, cities still pose a number of difficult challenges for both the scientific and end user stakeholder communities that are not adequately addressed by current meteorological observation, forecasting, and information dissemination technologies.
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58 58 URBAN METEOROLOGY FIGURE 3.1 Number of days that maximum temperature exceeded 100 degrees (F) from June 1 to August 31, 2011.
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SOURCE: Sue Grimmond and Bing Maps. R02149 Urban Meteorology Figure 3-2 bitmapped raster image
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R02149 Urban Meteorology Overall, urbanization results in a suite of complex land surface atmo Figure 3-3 sphere interactions that modify thermodynamic, radiative, dynamic, and bitmapped raster image hydrometeorological processes within the urban area and its surrounding regional footprint, particularly downwind of the city. Extreme weather and climate events in cities typically occur during unfavorable regional-scale conditions exacerbated by global warming trends and local, urban effects (Hunt et al., 2007)
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SCIENCE AND TECHNOLOGY 61 expected to become more frequent because of climate change, in combination with urban heat island development, exacerbate heat stress for urban populations (Zhou and Shepherd, 2009; Stone et al., 2010)
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Anthropogenic Greenhouse Gas (GHG) Urban Land Cover Urban Aerosols Emissions Urban Heat Surface Energy Budget Insolation, Direct R adiative Warming Island and Aerosol Effect and Feedbacks Mean Surface Temperature Record Wind Flow, Surface Energy Budget, Direct and Indirect Radiative Warming Dispersion, Urban Morphological Aerosol Effects and and Feedbacks Transport, and Parameters, Mechanical related dynamic/ Turbulence Turbulence, Bifurcated thermodynamic Flow response, Dispersion and Transport Clouds and Surface Energy Budget, Aerosol indirect effects Radiative Warming Precipitation UHI Destabilization, UHI on cloud-precipitation and Feedbacks Meso-circulations, UHI- microphysics, insolation induced convergence effects zones Land Surface Surface runoff, reduced Aerosol indirect effects Radiative warming Hydrology infiltration, less on cloud microphysical and feedbacks evapotranspiration and precipitation processes Carbon Cycle Replacement of Black carbon aerosols Radiative warming high net primary and feedbacks, fluxes productivity (NPP)
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. The RSL typically extends from the surface to a height equivalent to bitmapped raster image 2-5 times the average building height (Raupach et al., 1991; Rotach, 1999; Kastner-Klein and Rotach, 2004)
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Reprinted with permission. R02149 Urban Meteorology Figure 3-5 bitmapped raster image
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SCIENCE AND TECHNOLOGY 65 For large-scale weather patterns with weak dynamic forcings (i.e., weak winds) , urban flow patterns are primarily thermally driven, and a dome-like circulation pattern develops in cities that are located in flat terrain and away from large water bodies.
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ADVANCES IN URBAN FORECASTING AND MONITORING TECHNIQUES Meteorological observations and modeling are tightly coupled and require continual emergence of new understanding, measurements, and technology (Dabberdt abstract in Appendix A)
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SCIENCE AND TECHNOLOGY 67 (and even inclusive of it) , numerical weather prediction is the primary mechanism for forecasting.
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68 68 URBAN METEOROLOGY Urban Observation Networks Two National Research Council (NRC) reports (2008, 2010a)
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. Radiometric Profilers Ground-based microwave radiometric profilers are passive, multi-channel, all-weather systems that can measure profiles of atmospheric water vapor, temperature, and cloud liquid waters.
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Urban Land Cover Several remote sensing methodologies have emerged to delineate urban land cover. Satellite imagery comes from an array of platforms and instruments over the past 40 years.
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SCIENCE AND TECHNOLOGY 71 have been useful in characterizing the magnitude and extent of the UHI, land cover, and input for modeling systems connecting the atmosphere and land surface. Voogt and Oke (2003)
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SOURCE: NASA. R02149 Urban Meteorology Figure 3-6 bitmapped raster image
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Additionally, emerging modeling technologies that focus on coupling of models from global down to the microscale, or target specific end user applications such as exposure assessments and urban planning tools, are discussed later in this chapter. Urbanization of Numerical Weather Prediction Models One of the most important advances in urban meteorological forecasting in the last decade has been the development of urban surface energy balance and urban canopy models for Numerical Weather Prediction (NWP)
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74 74 URBAN METEOROLOGY for the urban effects on evaporation rates, absorption and reflection of solar radiation, and storage of heat, as well as wind and turbulence fields.
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There should be a "call for sharing" and coordination as it cannot be afforded that these resources remain underutilized. Atmospheric Dispersion and Urban Air Quality Models Two areas in which model development has been specifically targeted for improving the decision-making capabilities of end users are urban air quality (AQ)
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SOURCE: Patnaik et al., 2005. R02149 Urban Meteorology Figure 3-7
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aerosol feedbacks from CMAQ Figure 3-8 to the radiation budget, cloud microphysics, and precipitation in the me bitmapped raster image teorological model) and also has limitations because changes in the meteorological output variables happen over time scales of less than one hour.
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78 78 URBAN METEOROLOGY the Weather Research and Forecasting/Chemistry (WRF/Chem) model.
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The successful transition of such models into operations at major cities still needs to be seen. Hydrological Models Transformation of natural landscapes to urban impervious surfaces modifies surface runoff, evapotranspiration, infiltration, and groundwater recharge.
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80 80 URBAN METEOROLOGY of time and with greater volume, which can overwhelm capacity and lead to local flooding. Shepherd et al.
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EMERGING TECHNOLOGIES IN METEOROLOGICAL FORECASTING AND MONITORING Coupling Modeling Systems Use of High-Resolution Building Data Sets in Urban Weather and Climate Models As discussed earlier in this chapter, significant advances have been made to better represent cities in numerical weather prediction and air quality models. There are now several operational and research models that include urban canopy models.
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It is also important that efforts be undertaken to secure access and future development of NUDAPT. Coupling of Atmospheric Models from Global Down to Urban Scales Grimmond et al.
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They recommend that "attention be paid not only to characterizing accurately the structure of the urban area (e.g., height-to-width ratio) but also to ensuring that the input data reflect the thermal admittance properties of each of the city surfaces." Advanced Exposure Assessments Ambient concentrations from centrally located monitoring stations have been widely used as exposure surrogates (Sarnat et al., 2001; Burke et al., 2001; Ozkaynak et al., 2008)
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, while the regional transport and background con centrations are simulated with CMAQ. Application of Weather and Climate Models for Urban Planning At scales ranging from global to local, models are providing guidance on mitigation and adaptation decisions.
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This is partly because of the need for greater computing power, but also because end users are not typically educated on how to properly interpret model-generated probabilistic information, and modelers struggle with how best to communicate it. Data Assimilation Liu et al.
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. Probabilistic Forecasting Dabberdt and Miller (2000)
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noted several challenges that must be overcome before the user community can take advantage of probability forecasting, many of which are directly applicable to the urban meteorology problem. Advanced Sensing Techniques for the Atmospheric Boundary Layer Although there have been important recent advances in observation techniques that have resulted in clear improvements of weather forecasts, there is an obvious need for better observations, particularly to obtain highresolution profiles of atmospheric variables within the atmospheric/urban boundary layer.
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88 88 URBAN METEOROLOGY Non-Traditional Sensor Networks The unique form, population density, and attributes of urban environ ments make them particularly challenging from the standpoint of traditional meteorological observations. However, the same challenges associated with urban environments present opportunities as well.
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SCIENCE AND TECHNOLOGY 89 These capacities are primarily enabled by smart technologies such as GPS or mobile GIS capabilities, which are fairly ubiquitous in urban regions. Together, the combination of social media and personalized technology (via GPS receivers, smartphones, etc.)
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90 90 URBAN METEOROLOGY Stone et al.
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SCIENCE AND TECHNOLOGY 91 current deficiencies in model frameworks, physics, and dynamics while avoiding a plethora of poorly validated models that are not compatible or easily implemented in operational settings because of their complexity and the number and type of input parameters needed, (2) advancing air chemistry models and better coupling with weather models to improve predictions of particulates and other harmful atmospheric pollutants, and (3)
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