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Heat balance of an asphalt surface: observations and physically-based simulations
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
2006 (English)In: Meteorological Applications, ISSN 1350-4827, E-ISSN 1469-8080, Vol. 13, no 2, 203-212 p.Article in journal (Refereed) Published
Abstract [en]

A physically-based 1-D beat and mass transfer model was tested to estimate the beat fluxes of an asphalt surface. The model was run for two summer months for a road test site in southwest Sweden. Parameters for thermal properties, surface runoff, radiation and turbulent transfer were obtained from a description of the road stratification and from the literature. Coefficients of determination (r(2)) 0.94, 0.93 and 0.97 were obtained when simulated results were compared with observations of net radiation, beat flow below the surface and surface temperature respectively, all with slope coefficients close to unity. In addition, simulation results elucidated the robe of water vapour transport through the asphalt-soil profile and its effect on the latent beat flow from the surface. Problems were identified with closure of the beat balance in measurements based on discrepancy between simulated and observed sensible heat flux.

Place, publisher, year, edition, pages
2006. Vol. 13, no 2, 203-212 p.
Keyword [en]
CoupModel, energy balance, road, transport, bare-soil, numerical-model, temperature, parameterization, evaporation, prediction, moisture, ice
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:kth:diva-15795DOI: 10.1017/s1350482706002179ISI: 000238662200008ScopusID: 2-s2.0-33748130507OAI: diva2:333837
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-09-01Bibliographically approved
In thesis
1. Urban microclimate and surface hydrometeorological processes
Open this publication in new window or tab >>Urban microclimate and surface hydrometeorological processes
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The urban near surface atmosphere is of great concern since it affects the climate to which an increasing amount of people are immediately exposed. This study investigated the microclimate in central Stockholm in terms of the thermal conditions in the 0-2.5 m air layer and the water and heat exchange processes at different types of surfaces found within the urban environment. The main objective was to improve our understanding of the urban small-scale climate system.

The urban microclimate was measured in terms of vertical air temperature profiles along a horizontal transect running through a vegetated park and its built-up surroundings during three clear and relatively calm summer days. The results showed that the air temperature at 1.2 m height within the park was 0.5 to 1.5 K lower than in the surrounding city blocks, and that the thermal stratification was generally stable (increasing temperature with height) in the park and unstable (decreasing temperature with height) in the built-up areas. In addition, there were a few examples of temperature gradients orientated in different directions within the lowest 2.5 m air layer, indicating horizontal advection between the park and the built-up areas. Climate conditions simulated with a three-dimensional microclimate model agreed well with observations and the model was therefore assumed to provide reasonable representations of important climate processes such as surface-air energy exchange processes. However, there were some discrepancies between observations and simulations that are discussed in terms of differences in real and modelled heat storage processes and wind conditions. Processes that need to be included for a more precise model description of areas such as the Stockholm environment include dynamic heat storage in buildings and dynamic wind forcing during the course of the simulation.

A soil-vegetation-atmosphere transfer model was used to study soil water transport, the surface energy balance of an asphalt surface, and the impact of urban climate on evapotranspiration. Based on model calibration to field measurements of soil water content in a till catchment outside Stockholm, new parameter values were estimated that can be used for water flow modelling of till soils. The heat fluxes of an asphalt surface were reliably simulated without knowledge of site-specific calibration and the model was useful in identifying problems with energy balance closure based on measurements only. Simulations of ‘urban’ modifications to the forcing climate conditions demonstrated that increased air temperature, and thereby increased vapour pressure deficit, had most effect on evapotranspiration from tall vegetation, while increased long-wave radiation raised grass evapotranspiration the most.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. viii, 24 p.
Trita-LWR. PHD, ISSN 1650-8602 ; 1027
CoupModel, ENVI-met, roughness sub-layer, urban heat island
National Category
Physical Geography
urn:nbn:se:kth:diva-3879 (URN)91-7178-295-8 (ISBN)
Public defence
2006-03-24, Sal D3, Lindstedtsvägen 5, Stockholm, 10:15
QC 20100901Available from: 2006-03-14 Created: 2006-03-14 Last updated: 2010-09-01Bibliographically approved

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