scholarly journals Impact of Urban Growth on Surface Climate: A Case Study in Oran, Algeria

2009 ◽  
Vol 48 (2) ◽  
pp. 217-231 ◽  
Author(s):  
Lahouari Bounoua ◽  
Abdelmounaine Safia ◽  
Jeffrey Masek ◽  
Christa Peters-Lidard ◽  
Marc L. Imhoff
Keyword(s):  
Land Use ◽  
Land Surface ◽  
Urban Areas ◽  
Hydrological Cycle ◽  
Total Carbon ◽  
Semiarid Region ◽  
Surface Model ◽  
Carbon Uptake ◽  
Mean Temperature ◽  
The Impact

Abstract The authors develop a land use map discriminating urban surfaces from other cover types over a semiarid region in North Africa and use it in a land surface model to assess the impact of urbanized land on surface energy, water, and carbon balances. Unlike in temperate climates where urbanization creates a marked heat island effect, this effect is not strongly marked in semiarid regions. During summer, the urban class results in an additional warming of 1.45°C during daytime and 0.81°C at night relative to that simulated for needleleaf trees under similar climate conditions. Seasonal temperatures show that urban areas are warmer than their surrounding areas during summer and slightly cooler in winter. The hydrological cycle is practically “shut down” during summer and is characterized by relatively large amounts of runoff in winter. The authors estimate the annual amount of carbon uptake to be 1.94 million metric tons with only 11.9% assimilated during the rainy season. However, if urbanization expands to reach 50% of the total area excluding forests, the annual total carbon uptake will decline by 35% and the July mean temperature would increase only 0.10°C relative to the current situation. In contrast, if urbanization expands to 50% of the total land excluding forests and croplands but all short vegetation is replaced by native broadleaf deciduous trees, the annual carbon uptake would increase by 39% and the July mean temperature would decrease by 0.9°C relative to the current configuration. These results provide guidelines for urban planners and land use managers and indicate possibilities for mitigating the urban heat.

scholarly journals Impact of Multitemporal Land Use and Land Cover Change on Land Surface Temperature Due to Urbanization in Hefei City, China

2021 ◽  
Vol 10 (12) ◽  
pp. 809
Author(s):  
Jing Sun ◽  
Suwit Ongsomwang
Keyword(s):  
Land Use ◽  
Land Cover ◽  
Surface Temperature ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Urban Areas ◽  
Decomposition Analysis ◽  
Lulc Change ◽  
Main Components ◽  
The Impact

Land surface temperature (LST) is an essential parameter in the climate system whose dynamics indicate climate change. This study aimed to assess the impact of multitemporal land use and land cover (LULC) change on LST due to urbanization in Hefei City, Anhui Province, China. The research methodology consisted of four main components: Landsat data collection and preparation; multitemporal LULC classification; time-series LST dataset reconstruction; and impact of multitemporal LULC change on LST. The results revealed that urban and built-up land continuously increased from 2.05% in 2001 to 13.25% in 2020. Regarding the impact of LULC change on LST, the spatial analysis demonstrated that the LST difference between urban and non-urban areas had been 1.52 K, 3.38 K, 2.88 K and 3.57 K in 2001, 2006, 2014 and 2020, respectively. Meanwhile, according to decomposition analysis, regarding the influence of LULC change on LST, the urban and built-up land had an intra-annual amplitude of 20.42 K higher than other types. Thus, it can be reconfirmed that land use and land cover changes due to urbanization in Hefei City impact the land surface temperature.

scholarly journals Representation of fire, land-use change and vegetation dynamics in the Joint UK Land Environment Simulator vn4.9 (JULES)

2019 ◽  
Vol 12 (1) ◽  
pp. 179-193 ◽  
Author(s):  
Chantelle Burton ◽  
Richard Betts ◽  
Manoel Cardoso ◽  
Ted R. Feldpausch ◽  
Anna Harper ◽  
...  
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Land Cover ◽  
Vegetation Cover ◽  
Land Surface ◽  
Vegetation Dynamics ◽  
Fire Disturbance ◽  
Substantial Contribution ◽  
Surface Model ◽  
The Impact

Abstract. Disturbance of vegetation is a critical component of land cover, but is generally poorly constrained in land surface and carbon cycle models. In particular, land-use change and fire can be treated as large-scale disturbances without full representation of their underlying complexities and interactions. Here we describe developments to the land surface model JULES (Joint UK Land Environment Simulator) to represent land-use change and fire as distinct processes which interact with simulated vegetation dynamics. We couple the fire model INFERNO (INteractive Fire and Emission algoRithm for Natural envirOnments) to dynamic vegetation within JULES and use the HYDE (History Database of the Global Environment) land cover dataset to analyse the impact of land-use change on the simulation of present day vegetation. We evaluate the inclusion of land use and fire disturbance against standard benchmarks. Using the Manhattan metric, results show improved simulation of vegetation cover across all observed datasets. Overall, disturbance improves the simulation of vegetation cover by 35 % compared to vegetation continuous field (VCF) observations from MODIS and 13 % compared to the Climate Change Initiative (CCI) from the ESA. Biases in grass extent are reduced from −66 % to 13 %. Total woody cover improves by 55 % compared to VCF and 20 % compared to CCI from a reduction in forest extent in the tropics, although simulated tree cover is now too sparse in some areas. Explicitly modelling fire and land use generally decreases tree and shrub cover and increases grasses. The results show that the disturbances provide important contributions to the realistic modelling of vegetation on a global scale, although in some areas fire and land use together result in too much disturbance. This work provides a substantial contribution towards representing the full complexity and interactions between land-use change and fire that could be used in Earth system models.

scholarly journals Impact of urban canopy meteorological forcing on aerosol concentrations

2018 ◽  
Author(s):  
Peter Huszar ◽  
Michal Belda ◽  
Jan Karlický ◽  
Tatsiana Bardachova ◽  
Tomas Halenka ◽  
...  
Keyword(s):  
Land Surface ◽  
Urban Areas ◽  
Urban Canopy ◽  
Specific Humidity ◽  
Surface Model ◽  
Meteorological Forcing ◽  
Turbulent Diffusion Coefficient ◽  
Temperature Impact ◽  
The Impact ◽  
Meteorological Effects

Abstract. The regional climate model RegCM4 extended with the land-surface model CLM4.5 was coupled to the chemistry transport model CAMx to analyze the impact of urban meteorological forcing on the surface fine aerosol (PM2.5) concentrations for summer conditions over the 2001–2005 period focusing on the area of Europe. Starting with the analysis of the meteorological modifications caused by urban canopy forcing we found significant increases of urban surface temperatures (up to 2–3 K), decrease of specific humidity (by up to 0.4–0.6 g/kg) reduction of wind speed (up to −1 m/s) and enhancement of vertical turbulent diffusion coefficient (up to 60–70 m2/s). 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 the individual aerosol components as well. The urban induced temperature changes resulted in decreases of PM2.5 by −1.5 to −2 μg/m3, while decreased urban winds resulted in increases by 1–2 μg/m3. The enhanced turbulence over urban areas results in decreases of PM2.5 by −2 μg/m3. The combined effect of all individual impact depends on the competition between the partial impacts and can reach up to −3 μg/m3 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 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 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.

Assessing the impact of the urban landscape on heat wave episodes: a case study of the Metropolitan Area of Barcelona.

2020 ◽  
Author(s):  
Gara Villalba ◽  
Sergi Ventura ◽  
Joan Gilabert ◽  
Alberto Martilli ◽  
Alba Badia
Keyword(s):  
Land Use ◽  
Heat Wave ◽  
Metropolitan Area ◽  
Land Surface ◽  
Urban Areas ◽  
Urban Landscape ◽  
Urban Land Use ◽  
Anthropogenic Heat ◽  
Surface Model

<p>Currently, around 54% of the world's population is living in urban areas and this number is projected to increase by 66% by 2050. In the past years, cities have been experiencing heat wave episodes that affect the population. As the modern urban landscape is continually evolving, with green spaces and parks becoming a more integral component and with suburbs expanding outward from city centres into previously rural, agricultural, and natural areas, we need tools to learn how to best implement planning strategies that minimize heat waves.  In this study we use the Weather and Research Forecasting model (WRF) with a multi-layer layer scheme, the Building Effect Parameterization (BEP) coupled with the Building Energy Model (BEP+BEM, Salamanca and Martilli, 2010) to take into account the energy consumption of buildings and anthropogenic heat generated by air conditioning systems. The urban canopy scheme takes into account city morphology (e.g. building and street canyon geometry) and surface characteristics (e.g. albedo, heat capacity, emissivity, urban/vegetation fraction). The Community Land Surface Model (CLM) is used in WRF that uses 16 different plant functional types (PFTs) as the basis for land-use differentiation.  Furthermore, we use the Local Climate Zones (LCZ) classification which has 11 urban land use categories with specific thermal, radiative and geometric parameters of the buildings and ground to compute the heat and momentum fluxes in the urban areas.  The objective is to validate the model and establish relationships between urban morphology and land use with temperature, so that the model can be used to simulate land use scenarios to investigate the effectiveness of different mitigation strategies to lower urban temperatures during the summer months.</p><p> </p><p>We test the methods with the Metropolitan Area of Barcelona (AMB) as a case study. The AMB is representative of the Mediterranean climate, with mild winters and hot summers. With a heterogeneous urban landscape, the AMB covers 636 km<sup>2 </sup>(34% built, 23% agricultural, and 31% vegetation) and has more than five million habitants. We simulate the heat wave that occurred in August 2018, during which temperatures stayed between 30 and 40ºC for five consecutive days and compare results with observed data from five different weather stations. We then simulate a potential scenario changing land surface from built to vegetation, in accordance with Barcelona´s strategic climate plan, and the potential impact the land use change has on reducing heat wave episodes.</p>

scholarly journals Impact of an improved WRF urban canopy model on diurnal air temperature simulation over northern Taiwan

2016 ◽  
Vol 16 (3) ◽  
pp. 1809-1822 ◽  
Author(s):  
Chuan-Yao Lin ◽  
Chiung-Jui Su ◽  
Hiroyuki Kusaka ◽  
Yuko Akimoto ◽  
Yang-Fan Sheng ◽  
...  
Keyword(s):  
Land Surface ◽  
Urban Areas ◽  
Urban Canopy ◽  
Anthropogenic Heat ◽  
Surface Model ◽  
Urban Canopy Model ◽  
Simulation Performance ◽  
The Impact ◽  
Canopy Model ◽  
Northern Taiwan

Abstract. This study evaluates the impact of urbanization over northern Taiwan using the Weather Research and Forecasting (WRF) Model coupled with the Noah land-surface model and a modified urban canopy model (WRF–UCM2D). In the original UCM coupled to WRF (WRF–UCM), when the land use in the model grid is identified as "urban", the urban fraction value is fixed. Similarly, the UCM assumes the distribution of anthropogenic heat (AH) to be constant. This may not only lead to over- or underestimation of urban fraction and AH in urban and non-urban areas, but spatial variation also affects the model-estimated temperature. To overcome the abovementioned limitations and to improve the performance of the original UCM model, WRF–UCM is modified to consider the 2-D urban fraction and AH (WRF–UCM2D).The two models were found to have comparable temperature simulation performance for urban areas, but large differences in simulated results were observed for non-urban areas, especially at nighttime. WRF–UCM2D yielded a higher correlation coefficient (R2) than WRF–UCM (0.72 vs. 0.48, respectively), while bias and RMSE achieved by WRF–UCM2D were both significantly smaller than those attained by WRF–UCM (0.27 and 1.27 vs. 1.12 and 1.89, respectively). In other words, the improved model not only enhanced correlation but also reduced bias and RMSE for the nighttime data of non-urban areas. WRF–UCM2D performed much better than WRF–UCM at non-urban stations with a low urban fraction during nighttime. The improved simulation performance of WRF–UCM2D in non-urban areas is attributed to the energy exchange which enables efficient turbulence mixing at a low urban fraction. The result of this study has a crucial implication for assessing the impacts of urbanization on air quality and regional climate.

scholarly journals Effect of Land Use Changes on the Urban Surface Temperature in Umuahia Town, Southeast, Nigeria

2021 ◽  
Vol 5 (2) ◽  
pp. 433-443
Author(s):  
F. Ike ◽  
I.C. Mbah ◽  
C.R. Otah ◽  
J. Babington ◽  
L. Chikwendu
Keyword(s):  
Land Use ◽  
Surface Temperature ◽  
Land Surface ◽  
Urban Areas ◽  
Land Use Changes ◽  
Temporal Distribution ◽  
Urban Surface ◽  
Temperature Profiles ◽  
Bare Land ◽  
The Impact

The land surfaces of hot-humid tropical urban areas are exposed to significant levels of solar radiation. Increased heat gain adds to different land surface temperature profiles in cities, resulting in different thermal discomfort thresholds. Using multi-temporal (1986, 2001, and 2017) landsat data, this study examined the impact of land use change on urban temperature profiles in Umuahia, Nigeria. The findings revealed that over time, built-up regions grow in surface area and temperature at the expense of other land use. The transfer matrix, showed that approximately 59.88 percent of vegetation and 8.23 percent of bareland were respectively changed into built up during the course of 31 years. The highest annual mean temperature in built-up regions was 21.50°C in 1986, 22.20°C in 2001, and 26.01°C in 2017. Transect profiles across the landuses reveals that surface Temperature rises slowly around water/vegetation and quickly over built-up and bare land area. The study observed drastic changes in land cover with a corresponding increase in surface temperature for the period between 1986 and 2017 with consistent decrease in water bodies and bare land in the study area. Overall, the spatio-temporal distribution of surface temperature in densely built up areas was higher than the adjacent rural surroundings, which is evidence of Urban Heat Island. The impact of landuse change on urban surface temperature profiles could provide detailed data to planners and decision makers in evaluating thermal comfort levels and other risk considerations in the study area.

scholarly journals Was Australia a sink or source of CO<sub>2</sub> in 2015? Data assimilation using OCO-2 satellite measurements

2021 ◽  
Vol 21 (23) ◽  
pp. 17453-17494
Author(s):  
Yohanna Villalobos ◽  
Peter J. Rayner ◽  
Jeremy D. Silver ◽  
Steven Thomas ◽  
Vanessa Haverd ◽  
...  
Keyword(s):  
Land Surface ◽  
Regional Scale ◽  
Surface Fluxes ◽  
In Situ Monitoring ◽  
Total Carbon ◽  
Carbon Surface ◽  
Surface Model ◽  
Carbon Uptake ◽  
Sparse Vegetation

Abstract. In this study, we present the assimilation of data from the Orbiting Carbon Observatory-2 (OCO-2) (land nadir and glint data, version 9) to estimate the Australian carbon surface fluxes for the year 2015. To perform this estimation, we used both a regional-scale atmospheric transport–dispersion model and a four-dimensional variational assimilation scheme. Our results suggest that Australia was a carbon sink of −0.41 ± 0.08 PgC yr−1 compared to the prior estimate 0.09 ± 0.20 PgC yr−1 (excluding fossil fuel emissions). Most of the carbon uptake occurred in northern Australia over the savanna ecotype and in the western region over areas with sparse vegetation. Analysis of the enhanced vegetation index (EVI) suggests that the majority of the carbon uptake over the savanna ecosystem was due to an increase of vegetation productivity (positive EVI anomalies) amplified by an anomalous increase of rainfall in summer. Further from this, a slight increase of carbon uptake in Western Australia over areas with sparse vegetation (the largest ecosystem in Australia) was noted due to increased land productivity in the area caused by positive rainfall anomalies. The stronger carbon uptake estimate in this ecosystem was partially due to the land surface model (CABLE-BIOS3) underestimating the gross primary productivity of the ecosystem. To evaluate the accuracy of our carbon flux estimates from OCO-2 retrievals, we compare our posterior concentration fields against the column-averaged carbon retrievals from the Total Carbon Column Observing Network (TCCON) and ground-based in situ monitoring sites located around our domain. The validation analysis against TCCON shows that our system is able to reduce bias mainly in the summer season. Comparison with surface in situ observations was less successful, particularly over oceanic monitoring sites that are strongly affected by oceanic fluxes and subject to less freedom by the inversion. For stations located far from the coast, the comparison with in situ data was more variable, suggesting difficulties matching the column-integrated and surface data by the inversion, most likely linked to model vertical transport. Comparison of our fluxes against the OCO-2 model intercomparison (MIP) was encouraging. The annual carbon uptake estimated by our inversion falls within the ensemble of the OCO-2 MIP global inversions and presents a similar seasonal pattern.

scholarly journals Was Australia a sink or source of CO<sub>2</sub> in 2015? Data assimilation using OCO-2 satellite measurements

2021 ◽  
Author(s):  
Yohanna Villalobos ◽  
Peter J. Rayner ◽  
Jeremy D. Silver ◽  
Steven Thomas ◽  
Vanessa Haverd ◽  
...  
Keyword(s):  
Land Surface ◽  
Carbon Sink ◽  
Dispersion Model ◽  
Regional Scale ◽  
Surface Fluxes ◽  
In Situ Monitoring ◽  
Total Carbon ◽  
Surface Model ◽  
Carbon Uptake

Abstract. In this study, we present the assimilation of data from the Orbiting Carbon Observatory-2 (OCO-2) to estimate the Australian CO2 surface fluxes for the year 2015. We used a regional-scale atmospheric transport-dispersion model and a four-dimensional variational assimilation scheme. Our results suggest that Australia was a carbon sink of −0.3 ± 0.09 PgC y−1 compared to the prior estimate 0.09 ± 0.17 PgC y−1 (excluding fossil fuel emissions). Most of the uptake occurred over northern savannas, the Mediterranean ecotype in southern Australia and the sparsely vegetated ecotype in central Australia. Our results suggest that the majority of the carbon uptake over Mediterranean was associated with positive EVI anomalies (relative to 2000–2014). However, the stronger posterior carbon uptake estimated over savanna and sparsely vegetated ecosystem was due primarily to underestimation of the gross primary productivity by the land surface model (CABLE-BIOS3 model). To evaluate the accuracy of our posterior flux estimates, we compare our posterior CO2 concentration simulations against the column- averaged carbon retrievals from the Total Carbon Column Observing Network (TCCON) and ground-based in-situ monitoring sites located around our Australia domain. In general, the performance of our posterior concentration compared well with TCCON observations, except when TCCON concentrations were dominated by ocean fluxes which were tightly constrained to their prior values. Comparisons with in-situ measurements also show encouraging results though with similar difficulties for coastal stations. For stations located far from the coast, the comparison with in situ data was more variable, suggesting difficulties to match the column-integrated and surface data by the inversion, most likely linked to model vertical transport.

scholarly journals Implications of Land Use Change on River Flow in South West England

10.29007/75p2 ◽  
2018 ◽  
Author(s):  
Lorena Liuzzo ◽  
Gabriele Freni
Keyword(s):  
Land Use ◽  
Water Resources ◽  
Urban Areas ◽  
River Flow ◽  
Hydrological Cycle ◽  
Land Use Changes ◽  
Positive Effects ◽  
South West ◽  
The Impact ◽  
South West England

Assessing the impacts of future changes in land use on the hydrological cycle is an important issue for the proper management of water resources, since land use changes have implications on both water quantity and quality. Land use changes, in particular the expansion of urban areas, can significantly affect river flow increasing flood risk, whereas, the development of woodland areas could have positive effects on the reduction of peak flow. The present study has been carried out to assess and quantify the impact of land use changes on the water resources of a river basin located in South West England. With this aim, a hydrological model has been applied to some land use scenarios. In particular, two scenarios have been investigated: the first includes the increase of agricultural areas and the decrease of woodlands, the second includes the increase of urban areas and the decrease of woodlands. Results showed that, in the area of study, river flow would likely to be affected by future land use changes, mainly in the case of urban areas increase.

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