Energy exchange in a dense urban environment – Part I: Temporal variability of long-term observations in central London

Kotthaus, Simone; Grimmond, Sue

doi:10.1016/j.uclim.2013.10.002

Cited by 120 publications

(127 citation statements)

References 50 publications

Supporting

Mentioning

113

Contrasting

Unclassified

Order By: Relevance

“…Oke et al 1999;Grimmond et al 2004;Christen and Vogt 2004;Offerle et al 2006b;Kotthaus and Grimmond 2014a). In Łódź, we found that most of the time the night-time flux is negative, however, in several months (e.g.…”

Section: Monthly Variability Of Turbulent Sensible Heat Fluxmentioning

confidence: 70%

“…Frequent precipitation and relatively low air temperature in July results in a decrease of Q H , which at noon has features characteristic of dense urban areas: the diurnal peak is observed 1-2 h later than the maximum of radiation balance; it turns negative several hours later than Q * . Even though in the city centre positive Q H is frequently observed throughout the day (Christen and Vogt 2004;Goldbach and Kuttler 2013;Kotthaus and Grimmond 2014a), in Łódź it is observed almost only in winter and during several months with frequent cold advection. When the Q H measurements are performed with eddy covariance techniques, the source area is relatively small and can cover relatively uniform surfaces, e.g.…”

Section: Discussionmentioning

confidence: 96%

“…This possibly results from low data availability for winter months, because results from other cities suggest that the lowest Q H is more likely to occur in winter (e.g. Christen and Vogt 2004;Goldbach and Kuttler 2013;Kotthaus and Grimmond 2014a). On the other hand, in the city centre the release of a large amount of additional heat from fuel combustion (transportation, heating), significantly enhances Q H , as even at night it remains positive, i.e.…”

Section: Monthly Variability Of Turbulent Sensible Heat Fluxmentioning

confidence: 98%

“…However, due to the lack of a sufficient amount of data it should not be considered as a rule that the lowest Q H always occurs in late autumn. The measurements of Q H from other city centres suggest that the lowest Q H is most likely to occur in winter (Christen and Vogt 2004;Goldbach and Kuttler 2013;Kotthaus and Grimmond 2014a). On the other hand, in densely built-up areas an addition of heat from fuel combustion could lead to an enhancement of Q H or even positive night-time Q H during winter (e.g.…”

Section: Monthly Variability Of Turbulent Sensible Heat Fluxmentioning

confidence: 99%

“…As a result the number of data available for cases with wet surface is significantly reduced for south, south-east, east and north-east directions. Kotthaus and Grimmond (2014a) showed that Bowen ratio can be reduced even 12 h after the rain. Therefore we decided to treat all observations from periods up to 12 h after the precipitation, as cases with wet surface, even though Crawford et al (2017) used only 3 h threshold for London.…”

Section: Dependence Of Turbulent Sensible Heat Flux On Wind Directionmentioning

confidence: 99%

See 4 more Smart Citations

Long-term Turbulent Sensible-Heat-Flux Measurements with a Large-Aperture Scintillometer in the Centre of Łódź, Central Poland

Zieliński

Fortuniak

Pawlak

et al. 2018

Boundary-Layer Meteorol

View full text Add to dashboard Cite

We investigate the area-averaged sensible heat flux (Q H ) obtained with a scintillometer along a 3.1-km path length over the city centre of Łódź, Central Poland. The annual cycle of Q H peaks in June but is lower by the middle of summer. In winter, due to a large amount of anthropogenic heat input, Q H remains positive all day long, with positive nighttime fluxes also found during months with frequent cold advection, e.g., June 2010. In the diurnal cycle of this flux, several features specific to urban areas are seen: the peak shifts 1-2 h after noon, the heat flux turns from positive to negative 1-2 h after sunset. In Łódź Q H was observed during inflow from the north and north-west, i.e. from the city centre. As this area is mostly covered with impervious materials, most of the heat exchanged between the ground and the overlying air is in the form of sensible heat flux. Under the conditions of inflow from the east and south-east, the maximum heat flux is approximately 100 W m −2 lower than during the inflow from the city centre, since more vegetation exists to the east and south-east of the scintillometer path. Cold and warm advection are found to be a vital factor in the observed heat-flux variability in the centre of Łódź.

show abstract

Section: Monthly Variability Of Turbulent Sensible Heat Fluxmentioning

confidence: 70%

Section: Discussionmentioning

confidence: 96%

Section: Monthly Variability Of Turbulent Sensible Heat Fluxmentioning

confidence: 98%

Section: Monthly Variability Of Turbulent Sensible Heat Fluxmentioning

confidence: 99%

Section: Dependence Of Turbulent Sensible Heat Flux On Wind Directionmentioning

confidence: 99%

See 3 more Smart Citations

Long-term Turbulent Sensible-Heat-Flux Measurements with a Large-Aperture Scintillometer in the Centre of Łódź, Central Poland

Zieliński

Fortuniak

Pawlak

et al. 2018

Boundary-Layer Meteorol

View full text Add to dashboard Cite

show abstract

Understanding Disaster Resilience

Abeling

Huq

Chang-Seng

et al. 2018

Framing Community Disaster Resilience

View full text Add to dashboard Cite

Heat, water and carbon exchanges in the tall megacity of Shanghai: challenges and results

Grimmond

Chang

et al. 2016

Intl Journal of Climatology

View full text Add to dashboard Cite

The observed surface energy balance fluxes are essential to improve model forecasting ability but such data are scarce for subtropical cities and urban areas with tall buildings. One year of eddy covariance flux data for an area within Shanghai with a wide range of building heights (8-150 m, mean by direction) are analysed by wind direction. Consideration is given to how to distinguish between local-and micro-scale fluxes. At the local-scale, median daily peaks of sensible heat flux occur in the early afternoon (winter: 87 W m −2 , spring: 205 W m −2 , summer: 292 W m −2 , autumn: 135 W m −2 ). The latent heat flux is small in winter (median daily maxima 21 W m −2 ) and slightly larger in spring, summer and autumn (49, 65, 49 W m −2 , respectively). The monthly mean daytime Bowen ratio under all-sky conditions ranges from 2 to 4.7. At this site, with predominately impervious surface (85% buildings/pavement, 14% vegetation), the enhancement of evaporation following rainfall usually lasts for about 12 h. Consistently larger Bowen ratios at the micro-scale than the local-scale are attributed to roughness effects and the impact of extensive areas of dry walls. The daily median CO 2 flux is dominated by traffic emissions, with two peaks associated with morning and evening rush hours. The data provide insights into urban surface controls on momentum, energy and carbon dynamics, with implications for urban planning strategies in the context of rapid global urbanization and climate change.

show abstract

Energy exchange in a dense urban environment – Part I: Temporal variability of long-term observations in central London

Cited by 120 publications

References 50 publications

Long-term Turbulent Sensible-Heat-Flux Measurements with a Large-Aperture Scintillometer in the Centre of Łódź, Central Poland

Long-term Turbulent Sensible-Heat-Flux Measurements with a Large-Aperture Scintillometer in the Centre of Łódź, Central Poland

Understanding Disaster Resilience

Heat, water and carbon exchanges in the tall megacity of Shanghai: challenges and results

Contact Info

Product

Resources

About