Urban parks, energy budgets, and surface temperatures

1981 ◽  
Vol 29 (4) ◽  
pp. 327-344 ◽  
Author(s):  
Patricia A. O'Rourke ◽  
W. H. Terjung
Keyword(s):  
Urban Parks ◽  
Energy Budgets ◽  
Surface Temperatures

scholarly journals Dew frequency across the US from a network of in situ radiometers

2019 ◽  
Vol 23 (2) ◽  
pp. 1179-1197 ◽  
Author(s):  
François Ritter ◽  
Max Berkelhammer ◽  
Daniel Beysens
Keyword(s):  
Similarity Theory ◽  
Bowen Ratio ◽  
Surface Characteristics ◽  
Dew Point ◽  
Energy Budgets ◽  
High Temporal Resolution ◽  
Surface Temperatures ◽  
Dew Formation ◽  
The Mean

Abstract. Dew formation is a ubiquitous process, but its importance to energy budgets or ecosystem health is difficult to constrain. This uncertainty arises largely because of a lack of continuous quantitative measurements on dew across ecosystems with varying climate states and surface characteristics. This study analyzes dew frequency from the National Ecological Observatory Network (NEON), which includes 11 grasslands and 19 forest sites from 2015 to 2017. Dew formation is determined at 30 min intervals using in situ radiometric surface temperatures from multiple heights within the canopy along with meteorological measurements. Dew frequency in the grasslands ranges from 15 % to 95 % of the nights with a strong linear dependency on the nighttime relative humidity (RH), while dew frequency in the forests is less frequent and more homogeneous (25±14 %, 1 standard deviation – SD). Dew mostly forms at the top of the canopy for the grasslands due to more effective radiative cooling and within the canopy for the forests because of higher within the canopy RH. The high temporal resolution of our data showed that dew duration reaches maximum values (∼6–15 h) for RH∼96 % and for a wind speed of ∼0.5ms-1, independent of the ecosystem type. While dew duration can be inferred from the observations, dew yield needs to be estimated based on the Monin–Obukhov similarity theory. We find yields of 0.14±0.12mmnight-1 (1 SD from nine grasslands) similar to previous studies, and dew yield and duration are related by a quadratic relationship. The latent heat flux released by dew formation is estimated to be non-negligible (∼10Wm-2), associated with a Bowen ratio of ∼3. The radiometers used here provide canopy-averaged surface temperatures, which may underestimate dew frequency because of localized cold points in the canopy that fall below the dew point. A statistical model is used to test this effect and shows that dew frequency can increase by an additional ∼5 % for both ecosystems by considering a reasonable distribution around the mean canopy temperature. The mean dew duration is almost unaffected by this sensitivity analysis. In situ radiometric surface temperatures provide a continuous, non-invasive and robust tool for studying dew frequency and duration on a fine temporal scale.

scholarly journals Characterization of the Thermal Structure inside an Urban Canyon: Field Measurements and Validation of a Simple Model

2013 ◽  
Vol 52 (1) ◽  
pp. 64-81 ◽  
Author(s):  
Lorenzo Giovannini ◽  
Dino Zardi ◽  
Massimiliano de Franceschi
Keyword(s):  
Solar Radiation ◽  
Energy Use ◽  
Thermal Structure ◽  
Climatic Conditions ◽  
Surface Fluxes ◽  
Urban Canyon ◽  
Energy Budgets ◽  
Traffic Light ◽  
Surface Temperatures ◽  
Air Temperatures

AbstractThe results of measurement campaigns are analyzed to investigate the thermal structure in an urban canyon and to validate a simplified model simulating the air and surface temperatures from surface energy budgets. Starting from measurements at roof-top level, the model provides time series of air and surface temperatures, as well as surface fluxes. Two campaigns were carried out in summer 2007 and in winter 2008/09 in a street of the city of Trento (Italy). Temperature sensors were placed at various levels near the walls flanking the canyon and on a traffic light in the street center. Furthermore, the atmosphere above the mean roof-top level was monitored by a weather station on top of a tower located nearby. Air temperatures near the walls, being strongly influenced by direct solar radiation, display considerable contrasts between the opposite sides of the canyon. On the other hand, when solar radiation is weak or absent, the temperature field remains mostly homogeneous. Moreover, air temperature inside the canyon is generally higher than above roof level, with larger differences during summertime. Air temperatures from the above street measurements are well simulated by the model in both seasons. Furthermore, the modeled surface temperatures are tested against a dataset of wall surface temperatures from the Advanced Tools for Rational Energy Use Towards Sustainability–Photocatalytic Innovative Coverings Applications for Depollution (ATREUS–PICADA) experiment, and a very good agreement is found. Results suggest that the model is a reliable and convenient tool for simplified assessment of climatic conditions occurring in urban canyons under various weather situations.

scholarly journals Human Energy Budget Modeling in Urban Parks in Toronto and Applications to Emergency Heat Stress Preparedness

2012 ◽  
Vol 51 (9) ◽  
pp. 1639-1653 ◽  
Author(s):  
Jennifer K. Vanos ◽  
Jon S. Warland ◽  
Terry J. Gillespie ◽  
Graham A. Slater ◽  
Robert D. Brown ◽  
...  
Keyword(s):  
Heat Stress ◽  
Heat Wave ◽  
Energy Budget ◽  
Meteorological Data ◽  
Radiant Energy ◽  
Empirical Support ◽  
Urban Parks ◽  
Energy Budgets ◽  
Future Research ◽  
Human Energy

AbstractThe current study tests applications of the Comfort Formula (COMFA) energy budget model by assessing the moderating effects of urban parks in contrast to streets, and it also looks at the influence of park types (“open” or “treed”). Exploration into energy budget modeling is based on empirical meteorological data collected in Toronto, Ontario, Canada, on fair-weather days plus the effects of a heat wave and climate change, at various metabolic activity levels. Park cooling temperature intensities ranged from 3.9° to 6.0°C, yet human energy budgets were more closely correlated to incoming solar radiation than to air temperature. A strong linear dependence was found, with absorbed radiation (correlation coefficient squared r2 = 0.858) explaining the largest fraction of energy budget output. Hence, although the four parks that were examined are classified as urban green space, the distinctive treed areas showed a greater budget decrease than did open park areas (−25.5 W m−2). The greatest difference in budget decrease was found when modeling the highest metabolic rate, giving −20 W m−2 for “whole park,” −32 W m−2 for treed sections, and −3 W m−2 in open park areas. These results are intuitive within energy budget modeling and indicate that blocking radiant energy is a vital aspect in lowering high budgets under the conditions tested. Strong empirical support was provided through successful prediction of emergency-response calls during a heat wave in Toronto (5–7 July 2010) and surrounding days. Calls were found to be significantly dependent on the energy budget estimations (r2 = 0.860). There is great potential for outdoor energy budget modeling as a meaningful guide to heat stress forecasting, future research, and application in bioclimatic urban design for improving thermal comfort.

scholarly journals Dew frequency across the US from a network of in situ radiometers

2018 ◽  
Author(s):  
François Ritter ◽  
Max Berkelhammer ◽  
Daniel Beysens
Keyword(s):  
Similarity Theory ◽  
Bowen Ratio ◽  
Surface Characteristics ◽  
Dew Point ◽  
Energy Budgets ◽  
High Temporal Resolution ◽  
Surface Temperatures ◽  
Dew Formation ◽  
The Mean

Abstract. Dew formation is a ubiquitous process but its importance to energy budgets or ecosystem health is difficult to constrain. This uncertainty arises largely because of a lack of continuous quantitative measurements on dew across ecosystems with varying climate states and surface characteristics. This study analyzes dew frequency from the National Ecological Observatory Network (NEON), which includes 11 grasslands and 19 forest sites from 2015 to 2017. Dew formation is determined at 30 min intervals using in situ radiometric surface temperatures from multiple heights within the canopy along with meteorological measurements. Dew frequency in the grasslands ranges from 15 % to 95 % of the nights with a strong linear dependency on the nighttime relative humidity (RH), while dew frequency in the forests is less frequent and more homogeneous (25 ± 14 %, 1 Standard Deviation). Dew mostly forms at the top of the canopy for the grasslands due to more effective radiative cooling and within canopy for the forests because of higher within canopy RH. The high temporal resolution of our data showed that dew duration reaches maximum values (~ 6–15 h) for RH ~ 96 % and for a wind speed of ~ 0.5 m s−1, independent of the ecosystem type. While dew duration can be directly assessed from the observations, dew yield needs to be estimated based on the Monin-Obukov Similarity Theory. We find yields of 0.14 ± 0.12 mm night−1 (1 SD from nine grasslands) similar to previous studies, and dew yield and duration are related by a quadratic relationship. The latent heat flux released by dew formation is estimated to be non-negligible (~ 10 W m−2), associated with a Bowen ratio of ~ 3. The radiometers used here provide canopy-averaged surface temperatures, which may underestimate dew frequency because of localized cold points in the canopy that fall below the dew point. A statistical model is used to test this effect and shows that dew frequency can increase by an additional ~ 5 % for both ecosystems by considering a reasonable distribution around the mean canopy temperature. The mean dew duration is almost unaffected by this sensitivity analysis. In-situ radiometric surface temperatures provide a continuous, non-invasive and robust tool for studying dew frequency and duration on a fine temporal scale.

Numerical simulation of the tree higro-thermal response in forest fire environment

2020 ◽  
pp. 57-65
Author(s):  
Eusébio Conceiçã ◽  
João Gomes ◽  
Maria Manuela Lúcio ◽  
Jorge Raposo ◽  
Domingos Xavier Viegas ◽  
...  
Keyword(s):  
Forest Fire ◽  
Numerical Study ◽  
Thermal Response ◽  
View Factor ◽  
Tree Model ◽  
Pine Tree ◽  
Surface Temperatures ◽  
Fire Environment ◽  
Fire Front ◽  
Heat Exchanges

This paper refers to a numerical study of the hypo-thermal behaviour of a pine tree in a forest fire environment. The pine tree thermal response numerical model is based on energy balance integral equations for the tree elements and mass balance integral equation for the water in the tree. The simulation performed considers the heat conduction through the tree elements, heat exchanges by convection between the external tree surfaces and the environment, heat exchanges by radiation between the flame and the external tree surfaces and water heat loss by evaporation from the tree to the environment. The virtual three-dimensional tree model has a height of 7.5 m and is constituted by 8863 cylindrical elements representative of its trunks, branches and leaves. The fire front has 10 m long and a 2 m high. The study was conducted taking into account that the pine tree is located 5, 10 or 15 m from the fire front. For these three analyzed distances, the numerical results obtained regarding to the distribution of the view factors, mean radiant temperature and surface temperatures of the pine tree are presented. As main conclusion, it can be stated that the values of the view factor, MRT and surface temperatures of the pine tree decrease with increasing distance from the pine tree in front of fire.

Application of pyrometer and standard sample to determine surface temperature of studied materials

2019 ◽  
pp. 9-13
Author(s):  
V.Ya. Mendeleyev ◽  
V.A. Petrov ◽  
A.V. Yashin ◽  
A.I. Vangonen ◽  
O.K. Taganov
Keyword(s):  
Composite Material ◽  
Surface Temperature ◽  
Relative Error ◽  
Wavelength Range ◽  
Standard Sample ◽  
A Priori ◽  
Temperature Changes ◽  
Surface Temperatures ◽  
Relative Errors ◽  
Normal Emissivity

Determining the surface temperature of materials with unknown emissivity is studied. A method for determining the surface temperature using a standard sample of average spectral normal emissivity in the wavelength range of 1,65–1,80 μm and an industrially produced Metis M322 pyrometer operating in the same wavelength range. The surface temperature of studied samples of the composite material and platinum was determined experimentally from the temperature of a standard sample located on the studied surfaces. The relative error in determining the surface temperature of the studied materials, introduced by the proposed method, was calculated taking into account the temperatures of the platinum and the composite material, determined from the temperature of the standard sample located on the studied surfaces, and from the temperature of the studied surfaces in the absence of the standard sample. The relative errors thus obtained did not exceed 1,7 % for the composite material and 0,5% for the platinum at surface temperatures of about 973 K. It was also found that: the inaccuracy of a priori data on the emissivity of the standard sample in the range (–0,01; 0,01) relative to the average emissivity increases the relative error in determining the temperature of the composite material by 0,68 %, and the installation of a standard sample on the studied materials leads to temperature changes on the periphery of the surface not exceeding 0,47 % for composite material and 0,05 % for platinum.

Reconstruction Of Urban Parks Of Culture And Rest Of The Soviet Period

2019 ◽  
pp. 61-65
Keyword(s):  
Public Space ◽  
Senior Citizens ◽  
Urban Parks ◽  
Public Spaces ◽  
Historical Background ◽  
Soviet Period ◽  
Limited Mobility ◽  
Functional Zoning ◽  
Functional Areas ◽  
The City

This article analyzes the main problems of urban public spaces, because today public spaces can determine the future of cities. It is noted that parks are multifunctional public spaces in the urban environment, as they are an important element of the citywide system of landscaping and recreation, perform health, cultural, educational, aesthetic and environmental functions. The article notes that the need for easily accessible and well-maintained urban parks remains, however, the state of parks in many cities of Russia remains unsatisfactory, requiring reconstruction. A brief historical background of the Park of Culture and Rest of the Soviet period in Omsk is expounded, the analysis of the existing territory of the Park is presented. It is revealed that the Park, being the largest public space in Omsk, does not meet the requirements of modern urbanism, although it represents a great potential for designing the space for the purpose of recreation of citizens. Performed functional zoning scheme of the territory of the Park in question, where its division into functional areas destined for active recreational users of the Park is presented, considered the interests of senior citizens, people with limited mobility, etc. Reconstruction of Parks of the Soviet period can provide the city with additional recreational opportunities, as well as increase its tourist attractiveness.

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