ORCID Profile
0000-0002-1870-5565
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Publisher: Copernicus GmbH
Date: 22-11-2022
DOI: 10.5194/ESSD-14-5157-2022
Abstract: Abstract. A total of 20 urban neighbourhood-scale eddy covariance flux tower datasets are made openly available after being harmonized to create a 50 site–year collection with broad ersity in climate and urban surface characteristics. Variables needed as inputs for land surface models (incoming radiation, temperature, humidity, air pressure, wind and precipitation) are quality controlled, gap-filled and prepended with 10 years of reanalysis-derived local data, enabling an extended spin up to equilibrate models with local climate conditions. For both gap filling and spin up, ERA5 reanalysis meteorological data are bias corrected using tower-based observations, accounting for diurnal, seasonal and local urban effects not modelled in ERA5. The bias correction methods developed perform well compared to methods used in other datasets (e.g. WFDE5 or FLUXNET2015). Other variables (turbulent and upwelling radiation fluxes) are harmonized and quality controlled without gap filling. Site description metadata include local land cover fractions (buildings, roads, trees, grass etc.), building height and morphology, aerodynamic roughness estimates, population density and satellite imagery. This open collection can help extend our understanding of urban environmental processes through observational synthesis studies or in the evaluation of land surface environmental models in a wide range of urban settings. These data can be accessed from 0.5281/zenodo.7104984 (Lipson et al., 2022).
Publisher: American Geophysical Union (AGU)
Date: 08-02-2022
DOI: 10.1029/2021GL096069
Abstract: Water storage plays an important role in mitigating heat and flooding in urban areas. Assessment of the water storage capacity of cities remains challenging due to the inherent heterogeneity of the urban surface. Traditionally, effective storage has been estimated from runoff. Here, we present a novel approach to estimate effective water storage capacity from recession rates of observed evaporation during precipitation‐free periods. We test this approach for cities at neighborhood scale with eddy‐covariance based latent heat flux observations from 14 contrasting sites with different local climate zones, vegetation cover and characteristics, and climates. Based on analysis of 583 drydowns, we find storage capacities to vary between 1.3 and 28.4 mm, corresponding to e ‐folding timescales of 1.8–20.1 days. This makes the urban storage capacity at least five times smaller than all the observed values for natural ecosystems, reflecting an evaporation regime characterized by extreme water limitation.
Publisher: Copernicus GmbH
Date: 31-01-2020
Abstract: Abstract. Increasing urbanization is likely to intensify the urban heat island effect, decrease outdoor thermal comfort, and enhance runoff generation in cities. Urban green spaces are often proposed as a mitigation strategy to counteract these adverse effects, and many recent developments of urban climate models focus on the inclusion of green and blue infrastructure to inform urban planning. However, many models still lack the ability to account for different plant types and oversimplify the interactions between the built environment, vegetation, and hydrology. In this study, we present an urban ecohydrological model, Urban Tethys-Chloris (UT& C), that combines principles of ecosystem modelling with an urban canopy scheme accounting for the biophysical and ecophysiological characteristics of roof vegetation, ground vegetation, and urban trees. UT& C is a fully coupled energy and water balance model that calculates 2 m air temperature, 2 m humidity, and surface temperatures based on the infinite urban canyon approach. It further calculates the urban hydrological fluxes in the absence of snow, including transpiration as a function of plant photosynthesis. Hence, UT& C accounts for the effects of different plant types on the urban climate and hydrology, as well as the effects of the urban environment on plant well-being and performance. UT& C performs well when compared against energy flux measurements of eddy-covariance towers located in three cities in different climates (Singapore, Melbourne, and Phoenix). A sensitivity analysis, performed as a proof of concept for the city of Singapore, shows a mean decrease in 2 m air temperature of 1.1 ∘C for fully grass-covered ground, 0.2 ∘C for high values of leaf area index (LAI), and 0.3 ∘C for high values of Vc,max (an expression of photosynthetic capacity). These reductions in temperature were combined with a simultaneous increase in relative humidity by 6.5 %, 2.1 %, and 1.6 %, for fully grass-covered ground, high values of LAI, and high values of Vc,max, respectively. Furthermore, the increase of pervious vegetated ground is able to significantly reduce surface runoff.
Publisher: Copernicus GmbH
Date: 05-09-2019
DOI: 10.5194/GMD-2019-225
Abstract: Abstract. Increasing urbanization is likely to intensify the urban heat island effect, decrease outdoor thermal comfort and enhance runoff generation in cities. Urban green spaces are often proposed as a mitigation strategy to counteract these adverse effects and many recent developments of urban climate models focus on the inclusion of green and blue infrastructure to inform urban planning. However, many models still lack the ability to account for different plant types and oversimplify the interactions between the built environment, vegetation, and hydrology. In this study, we present an urban ecohydrological model, Urban Tethys-Chloris (UT& C), that combines principles of ecosystem modelling with an urban canopy scheme accounting for the biophysical and ecophysiological characteristics of roof vegetation, ground vegetation and urban trees. UT& C is a fully coupled energy and water balance model that calculates 2 m air temperature, 2 m humidity, and surface temperatures based on the infinite urban canyon approach. It further calculates all urban hydrological fluxes, including transpiration as a function of plant photosynthesis. Hence, UT& C accounts for the effects of different plant types on the urban climate and hydrology, as well as the effects of the urban environment on plant well-being and performance. UT& C performs well when compared against energy flux measurements of eddy covariance towers located in three cities in different climates (Singapore, Melbourne, Phoenix). A sensitivity analysis, performed as a proof of concept for the city of Singapore, shows a mean decrease in 2 m air temperature of 1.1 °C for fully grass covered ground, 0.2 °C for high values of leaf area index (LAI), and 0.3 °C for high values of Vc,max (an expression of photosynthetic activity). These reductions in temperature were combined with a simultaneous increase in relative humidity by 6.5 %, 2.1 %, and 1.6 %, for fully grass covered ground, high values of LAI, and high values of Vc,max, respectively. Furthermore, the increase of pervious vegetated ground is able to significantly reduce surface runoff. These results show that urban greening can lead to a decrease in urban air temperature and surface runoff, but this effect is limited in cities characterized by a hot, humid climate.
Publisher: Wiley
Date: 23-06-2021
Publisher: Wiley
Date: 22-09-2021
Publisher: Wiley
Date: 26-03-2021
Publisher: Copernicus GmbH
Date: 03-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-2765
Abstract: & & The amount and dynamics of urban water storage play an important role in mitigating urban flooding and heat. Assessment of the capacity of cities to store water remains challenging due to the extreme heterogeneity of the urban surface. Evapotranspiration (ET) recession after rainfall events during the period without precipitation, over which the amount of stored water gradually decreases, can provide insight on the water storage capacity of urban surfaces. Assuming ET is the only outgoing flux, the water storage capacity can be estimated based on the timescale and intercept of its recession. In this paper, we test the proposed approach to estimate the water storage capacity at neighborhood scale with latent heat flux data collected by eddy covariance flux towers in eleven contrasting urban sites with different local climate zones, vegetation cover and characteristics and background climates (Amsterdam, Arnhem, Basel, Berlin, Helsinki, & #321 & #243 d& #378 , Melbourne, Mexico City, Seoul, Singapore, Vancouver). Water storage capacities ranging between 1 and 12 mm were found. These values correspond to e-folding timescales lasting from 2 to 10 days, which translate to half-lives of 1.5 to 7 days. We find ET at the start of a drydown to be positively related to vegetation fraction, and long timescales and large storage capacities to be associated with higher vegetation fractions. According to our results, urban water storage capacity is at least one order of magnitude smaller than the known water storage capacity in natural forests and grassland.& &
Publisher: Copernicus GmbH
Date: 03-06-2022
DOI: 10.5194/ESSD-2022-65
Abstract: Abstract. Twenty urban neighbourhood-scale eddy covariance flux tower datasets have been harmonized and quality controlled, producing a 50 site-year collection with broad ersity in climate and urban surface characteristics. Observations are gap-filled and prepended with 10 years of reanalysis-derived local data to enable use as spin up and forcing for land surface model evaluation. For both gap filling and spin-up, ERA5 reanalysis meteorological data are bias corrected using tower observations, accounting for diurnal, seasonal and local urban effects not modelled in ERA5. The bias correction methods developed perform well compared to methods used in other datasets (e.g. WFDE5 or FLUXNET2015 linear regression). Site description metadata includes local land cover fractions (buildings, roads, trees, grass etc.), building height and morphology, aerodynamic roughness estimates, population density and satellite imagery. Together, this collection can help extend our understanding of urban environmental processes through observational synthesis studies or in the evaluation of land surface environmental models in a wide range of urban settings.
Publisher: Copernicus GmbH
Date: 05-09-2019
Location: United States of America
Location: Singapore
No related grants have been discovered for Erik Velasco.