| 1. |
|
|
| 2. |
- Eliasson, Ingegärd, 1961, et al.
(författare)
-
Wind fields and turbulence statistics in an urban street canyon
- 2006
-
Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 40:1, s. 1-16
-
Tidskriftsartikel (refereegranskat)abstract
- This is the first paper of a long-term measurement campaign to explore wind, temperature, radiation and energy fieldswithin an urban canyon. A canyon and a rooftop mast were installed in a canyon with an aspect ratio (Height/Width)of 2.1 in Goteborg, Sweden. A number of instruments including sonic anemometers, radiometers and thermocoupleswere mounted in vertical profiles and across the width of the canyon. The experimental set-up, the characteristics of thecanyon flow pattern and mean and turbulence statistics with respect to above canyon flow are examined using datacollected under clear-sky conditions in summer and autumn 2003. Results show that under cross-canyon (within 601 oforthogonal) flow, a single helical vortex exists. High temporal resolution analysis suggests that eddies frequentlypenetrate the shear stress layer at the canyon top disrupting established flow patterns. A combination of complexbuilding roof shapes and local topography may contribute to this effect by maintaining a high degree of turbulence. Theprofile of mean wind speed within the canyon and the relation with that above canyon depends on the ambient flowdirection in relation to the canyon long axis. Turbulence statistics show results similar to other field studies, withturbulence kinetic energy and vertical mixing greatest toward the windward wall.
|
|
| 3. |
- Evyatar, E, et al.
(författare)
-
Incorporating spatial and temporal variations of advected moisture in the canyon air temperature (CAT) model.
- 2009
-
Ingår i: ICUC7 Proceedings.
-
Konferensbidrag (refereegranskat)abstract
- CAT (Canyon Air Temperature) is a parametric model that predicts site-specific air temperature in an urban street canyon for extended periods on the basis of data from a reference station in the region. A method is described for incorporating spatial and temporal variations in advected moisture, allowing application of the model with no prior knowledge of moisture availability in the area. The revised model is tested against data from field experiments in Gothenburg and Adelaide, in all seasons and in a variety of atmospheric conditions.
|
|
| 4. |
- Lordian, Thomas, et al.
(författare)
-
Local-Scale Urban Meteorological Parameterization Scheme (LUMPS): longwave radiation parameterization and seasonality related developments
- 2011
-
Ingår i: Journal of Applied Meteorology and Climatology. - 1558-8424 .- 1558-8432. ; 50, s. 185-202
-
Tidskriftsartikel (refereegranskat)abstract
- Recent developments to the Local-scale Urban Meteorological Parameterization Scheme (LUMPS), a simple model able to simulate the urban energy balance are presented. The major development is the coupling of LUMPS to the Net All-Wave Radiation Parameterization (NARP). Others include that the model now accounts for: changing availability of water at the surface; seasonal variations of active vegetation; and the anthropogenic heat flux; while maintaining the need for only commonly available meteorological observations and basic surface characteristics. The incoming component of the longwave radiation (L↓) in NARP is improved through a simple relation derived using cloud cover observations from a ceilometer collected in central London. The new L↓ formulation is evaluated with two independent multi-year datasets (Łódź, Poland and Baltimore, USA) and compared to alternatives that include: the original NARP and a simpler one using the U. S. National Climatic Data Center cloud observation database as input. The performance for the surface energy balance fluxes is assessed using a two year dataset (Łódź). Results have an overall RMSE
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Offerle, Brian, 1967, et al.
(författare)
-
Surface heating in relation to air temperature, wind and turbulence in an urban street canyon
- 2007
-
Ingår i: Boundary-Layer Meteorology. - : Springer Science and Business Media LLC. - 0006-8314 .- 1573-1472. ; 122:2, s. 273-292
-
Tidskriftsartikel (refereegranskat)abstract
- Wind and temperature measurements from within and above a deep urban canyon (height/width = 2.1) were used to examine the thermal structure of air within the canyon, exchange of heat with the overlying atmosphere, and the possible impacts of surface heating on within-canyon air flow. Measurements were made over a range of seasons and primarily analysed for sunny days. This allowed the study of temperature differences between opposing canyon walls and between wall and air of more than 15 degrees C in summer. The wall temperature patterns follow those of incoming solar radiation loading with a secondary daytime effect from the longwave exchange between the walls. In winter, the canyon walls receive little direct solar radiation, and temperature differences are largely due to anthropogenic heating of the building interiors. Cool air from aloft and heated air from canyon walls is shown to circulate within the canyon under cross-canyon flow. Roofs and some portions of walls heat up rapidly on clear days and have a large influence on heat fluxes and the temperature field. The magnitude and direction of the measured turbulent heat flux also depend strongly on the direction of flow relative to surface heating. However, these spatial differences are smoothed by the shear layer at the canyon top. Buoyancy effects from the heated walls were not seen to have as large an impact on the measured flow field as has been shown in numerical experiments. At night canyon walls are shown to be the source of positive sensible heat fluxes. The measurements show that materials and their location, as well as geometry, play a role in regulating the heat exchange between the urban surface and atmosphere.
|
|
| 8. |
|
|
| 9. |
- Offerle, Brian, 1967, et al.
(författare)
-
Urban modification of the surface energy balance in the West African Sahel: Ouagadougou, Burkina Faso
- 2005
-
Ingår i: Journal of Climate. - 0894-8755 .- 1520-0442. ; 18:19, s. 3983-3995
-
Tidskriftsartikel (refereegranskat)abstract
- Surface-atmosphere energy exchanges in Ouagadougou, Burkina Faso, located in the West African Sahel, were investigated during February 2003. Basic knowledge of the impact of land cover changes on local climate is needed to understand and forecast the impacts of rapid urbanization predicted for the region. Previously collected data showed a large dry season urban heat island (UHI), which dramatically decreased with the onset of the rainy season and corresponding changes to the natural land cover thermal and radiative properties. Observations of local-scale energy balance fluxes were made over a residential district; and building surface temperatures were measured in three separate locations. Net all-wave radiation showed an increase with urbanization owing to the higher albedo, lower heat capacity, and thermal conductivity of the bare dry soil compared to the urbanized surface. The combination of material and geometry resulted in a decrease in albedo toward the urban center. Despite the higher albedo, surface temperatures of bare undisturbed soil could exceed surface temperatures in the residential area and urban center by 15 degrees-20 degrees C due to differences in thermal characteristics. Turbulent heat exchange measured over a residential area was dominated by sensible heat flux. Latent heat fluxes were greater than expected from the amount of vegetation but in accordance with water use in the area. An urban land surface scheme reproduced fluxes in agreement with measurements. The results point toward an intensification of the dry season urban heat island in Ouagadougou, given increased urbanization.
|
|
