Validation and results of a scale model of dew deposition in urban environments

Richards, Keith; Oke, T. R.

doi:10.1002/joc.856

Cited by 31 publications

(16 citation statements)

References 33 publications

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“…In rural areas during night, temperature drops often under dew-point resulting in condensation which act as a sink. This does not occur however at such extend in urban areas, where a reduced dew deposition has been observed in correspondence with the expectations (Richards and Oke, 2002). Hence, urban 25 nighttime absolute humidity can be slightly higher, than the rural one, at least near the surface.…”

supporting

confidence: 63%

Impact of urban canopy meteorological forcing on aerosol concentrations

Huszár¹,

Belda²,

Karlický³

et al. 2018

Preprint

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).These modifications translated into significant changes in surface aerosol concentrations that were calculated by "cascading" experimental approach. First, none of the urban meteorological effects were considered. Than, the temperature effect was added, than the humidity, the wind and finally, the enhanced turbulence was considered in the chemical runs. This facilitated the understanding of the underlying processes acting to modify urban aerosol concentrations. Moreover, we looked at the impact of for some cities, especially were the temperature impact was stronger in magnitude than the wind impact. The effect of changed humidity was found to be minor. The main contributor to the temperature impact is 15 the modification of secondary inorganic aerosols, mainly nitrates, while the wind and turbulence impact is most pronounced in case of primary aerosol (primary black and organic carbon and other fine particle matter). The overall as well as individual impacts on secondary organic aerosol is very small with the increased turbulence acting as the main driver. The analysis of the vertical extend of the aerosol changes showed that the perturbations caused by urban canopy forcing, besides being large near the surface, have a secondary maximum for turbulence and wind impact over higher model levels, which is attributed to the 20 vertical extend of the changes in turbulence over urban areas. The validation of model data with measurements showed good agreement and we could detect a clear model improvement at some areas when including the urban canopy meteorological effects in our chemistry simulations.1 Atmos. Chem. Phys. Discuss., https://doi

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supporting

confidence: 63%

Impact of urban canopy meteorological forcing on aerosol concentrations

Huszár¹,

Belda²,

Karlický³

et al. 2018

Preprint

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“…The upward-directed turbulent flux densities and a modified turbulent exchange finally result in a nocturnal urban heat island, with T U -R between +2 and +3 K in the city of Basel (Section 3.3.1, Figure 3(b)). The combination of reduced urban moisture availability, nocturnal heat island, and unstable near-surface layer explains the often observed reduction of dewfall (Richards and Oke, 2002;Richards, 2004) and reduction of radiation fog within cities (Sachweh and Koepke, 1995).…”

Section: Daily Variationsmentioning

confidence: 99%

Energy and radiation balance of a central European city

Christen

Vogt

2004

Intl Journal of Climatology

389

297

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Results from an experimental network of seven energy balance stations in and around a European city are presented. The network of micrometeorological stations was part of the Basel Urban Boundary Layer Experiment (BUBBLE) carried out in the city of Basel, Switzerland. Three urban sites provided turbulent flux densities and radiation data over dense urban surfaces. Together with a suburban site and three rural reference sites, this network allowed the simultaneous comparison of urban, suburban, and rural energy balance partitioning during one month of summertime measurements. The partitioning is analysed together with long-term data to evaluate the magnitude of the urban flux density modification, and to document characteristic values in their diurnal and yearly course. Simple empirical relations between flux densities and surface characteristics are presented. The energy balance partitioning is addressed separately for daytime and nocturnal situations. All four components of the surface radiation budget are analysed. Moreover, the vertical flux density divergences within the urban canopy layer are discussed.

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“…Urban surfaces have further impacts on other meteorological parameters as well: Richards and Oke (2002) and Richards (2004) studied the changes of surface humidity, while Grimmond and Oke (2002), Roth (2000) or KastnerKlein et al (2001) focused on the impact on roughness and turbulence. Many studies dealt with the structure of the urban boundary layer including the impact on the height of the planetary boundary layer (ZPBL) (Piringer, 2001;Cleugh and Grimmond, 2001;Martilli, 2002;Angevine et al, 2003;Nair et al, 2004) and wind speed (Hou et al, 2013).…”

Section: Published By Copernicus Publications On Behalf Of the Europementioning

confidence: 99%

Regional climate model assessment of the urban land-surface forcing over central Europe

et al. 2014

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Abstract. For the purpose of qualifying and quantifying the climate impact of cities and urban surfaces in general on climate of central Europe, the surface parameterization in regional climate model RegCM4 has been extended with the Single-layer Urban Canopy Model (SLUCM). A set of experiments was performed over the period of 2005-2009 for central Europe, either without considering urban surfaces or with the SLUCM treatment. Results show a statistically significant impact of urbanized surfaces on temperature (up to 1.5 K increase in summer) as well as on the boundary layer height (increases up to 50 m). Urbanization further influences surface wind with a winter decrease up to −0.6 m s −1 , though both increases and decreases were detected in summer depending on the location relative to the cities and daytime (changes up to 0.3 m s −1 ). Urban surfaces significantly reduce the humidity over the surface. This impacts the simulated summer precipitation rate, showing a decrease over cities of up to −2 mm day −1 . Significant temperature increases are simulated over higher altitudes as well, not only within the urban canopy layer. With the urban parameterization, the climate model better describes the diurnal temperature variation, reducing the cold afternoon and evening bias of RegCM4.Sensitivity experiments were carried out to quantify the response of the meteorological conditions to changes in the parameters specific to the urban environment, such as street width, building height, albedo of the roofs and anthropogenic heat release. The results proved to be rather robust and the choice of the key SLUCM parameters impacts them only slightly (mainly temperature, boundary layer height and wind velocity).Statistically significant impacts are modelled not only over large urbanized areas, but the influence of the cities is also evident over rural areas without major urban surfaces. It is shown that this is the result of the combined effect of the distant influence of the cities and the influence of the minor local urban surface coverage.

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Validation and results of a scale model of dew deposition in urban environments

Cited by 31 publications

References 33 publications

Impact of urban canopy meteorological forcing on aerosol concentrations

Impact of urban canopy meteorological forcing on aerosol concentrations

Energy and radiation balance of a central European city

Regional climate model assessment of the urban land-surface forcing over central Europe

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