scholarly journals A Model for Urban Biogenic CO<sub>2</sub> Fluxes: Solar-Induced Fluorescence for Modeling Urban biogenic Fluxes (SMUrF v1)

2020 ◽  
Author(s):  
Dien Wu ◽  
John C. Lin ◽  
Henrique F. Duarte ◽  
Vineet Yadav ◽  
Nicholas C. Parazoo ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Urban Areas ◽  
Fossil Fuel ◽  
Ecosystem Respiration ◽  
Growing Season ◽  
Carbon Fluxes ◽  
Co2 Fluxes ◽  
Biogenic Carbon ◽  
Urban Rural ◽  
Biogenic Fluxes

Abstract. When estimating fossil fuel carbon dioxide (FFCO2) emissions from observed CO2 concentrations, the accuracy can be hampered by biogenic carbon exchanges during the growing season even for urban areas where strong fossil fuel emissions are found. While biogenic carbon fluxes have been studied extensively across natural vegetation types, biogenic carbon fluxes within an urban area have been challenging to quantify due to limited observations and differences between urban versus rural regions. Here we developed a simple model representation, i.e., Solar-Induced Fluorescence (SIF) for Modeling Urban biogenic Fluxes ("SMUrF"), that estimates the gross primary production (GPP) and ecosystem respiration (Reco) over cities around the globe. Specifically, we leveraged space-based SIF, machine learning, eddy-covariance flux data, and additional remote sensing-based products, and developed algorithms to gap fill fluxes for urban areas. Grid-level hourly mean net ecosystem exchange (NEE) are extracted from SMUrF and evaluated against 1) non-gapfilled measurements at 67 eddy-covariance (EC) sites from FLUXNET during 2010–2014 (r > 0.7 for most data-rich biomes), 2) independent observations at two urban vegetation and two crop EC sites over Indianapolis from Aug 2017 to Dec 2018 (r = 0.75), and 3) an urban biospheric model based on fine-grained land cover classification within Los Angeles (r = 0.83). Moreover, we compared SMUrF-based NEE with inventory-based FFCO2 emissions over 40 cities and addressed the urban-rural contrast regarding both the magnitude and timing of CO2 fluxes. By examining a few summertime satellite tracks over four cities, we found that the urban-rural gradient in column CO2 (XCO2) anomalies due to NEE can sometimes reach ~ 0.5 ppm and be close to XCO2 enhancements due to FFCO2 emissions. With rapid advances in space-based measurements and increased sampling of SIF and CO2 measurements over urban areas, SMUrF can be useful for informing the biogenic CO2 fluxes over highly vegetated regions during the growing season.

scholarly journals A model for urban biogenic CO<sub>2</sub> fluxes: Solar-Induced Fluorescence for Modeling Urban biogenic Fluxes (SMUrF v1)

2021 ◽  
Vol 14 (6) ◽  
pp. 3633-3661
Author(s):  
Dien Wu ◽  
John C. Lin ◽  
Henrique F. Duarte ◽  
Vineet Yadav ◽  
Nicholas C. Parazoo ◽  
...  
Keyword(s):  
Urban Areas ◽  
Fossil Fuel ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Growing Season ◽  
Carbon Fluxes ◽  
Co2 Fluxes ◽  
Biogenic Carbon ◽  
Urban Rural ◽  
Biogenic Fluxes

Abstract. When estimating fossil fuel carbon dioxide (FFCO2) emissions from observed CO2 concentrations, the accuracy can be hampered by biogenic carbon exchanges during the growing season, even for urban areas where strong fossil fuel emissions are found. While biogenic carbon fluxes have been studied extensively across natural vegetation types, biogenic carbon fluxes within an urban area have been challenging to quantify due to limited observations and differences between urban and rural regions. Here we developed a simple model representation, i.e., Solar-Induced Fluorescence (SIF) for Modeling Urban biogenic Fluxes (“SMUrF”), that estimates the gross primary production (GPP) and ecosystem respiration (Reco) over cities around the globe. Specifically, we leveraged space-based SIF, machine learning, eddy-covariance (EC) flux data, and ancillary remote-sensing-based products, and we developed algorithms to gap-fill fluxes for urban areas. Grid-level hourly mean net ecosystem exchange (NEE) fluxes are extracted from SMUrF and evaluated against (1) non-gap-filled measurements at 67 EC sites from FLUXNET during 2010–2014 (r>0.7 for most data-rich biomes), (2) independent observations at two urban vegetation and two crop EC sites over Indianapolis from August 2017 to December 2018 (r=0.75), and (3) an urban biospheric model based on fine-grained land cover classification in Los Angeles (r=0.83). Moreover, we compared SMUrF-based NEE with inventory-based FFCO2 emissions over 40 cities and addressed the urban–rural contrast in both the magnitude and timing of CO2 fluxes. To illustrate the application of SMUrF, we used it to interpret a few summertime satellite tracks over four cities and compared the urban–rural gradient in column CO2 (XCO2) anomalies due to NEE against XCO2 enhancements due to FFCO2 emissions. With rapid advances in space-based measurements and increased sampling of SIF and CO2 measurements over urban areas, SMUrF can be useful to inform the biogenic CO2 fluxes over highly vegetated regions during the growing season.

scholarly journals Diurnal, weekly, seasonal and spatial variabilities in carbon dioxide flux in different urban landscapes in Sakai, Japan

2016 ◽  
Author(s):  
Masahito Ueyama ◽  
Tomoya Ando
Keyword(s):  
Rural Area ◽  
Eddy Covariance ◽  
Co2 Emissions ◽  
Air Temperature ◽  
Urban Areas ◽  
Suburban Area ◽  
Urban Park ◽  
Urban Landscapes ◽  
Co2 Fluxes ◽  
Urban Center

Abstract. To evaluate CO2 emissions in urban areas and their temporal and spatial variabilities, continuous measurements of CO2 fluxes were conducted using the eddy covariance method at three locations in Sakai, Osaka, Japan. Based on the flux footprint at the measurement sites, CO2 fluxes from the three sites were partitioned into five datasets representing a dense urban center, a moderately urban area, a suburb, an urban park, and a rural area. Distinct biological uptake of CO2 was observed in the suburb, urban park, and rural areas in the daytime, whereas high emissions were observed at dense and moderate urban areas in daytime. Weekday CO2 emissions in the dense urban center and suburban area were approximately 50 % greater than during weekend and holidays, but the other landscapes did not exhibit a clear weekly cycle. Seasonal variations in the urban park, rural area, and suburban area were influenced by vegetation activities, exhibiting the lowest daily emissions or even uptakes during summer months. In contrast, the dense and moderately urban areas exhibited higher emissions in winter and summer months, when emissions significantly increased as air temperature increased in summer and air temperature decreased in winter. Irrespective of the landcover type, all urban landscapes measured in this study acted as net annual CO2 sources, with emissions ranging from 0.5 to 4.9 kg C m−2 yr−1. The magnitude of the annual CO2 emissions was negatively correlated with green fraction; areas with a smaller green fraction had higher annual CO2 emissions. Upscaled flux estimates based on the green fraction indicated that the emissions for the entire city were 3.3 kg C m−2 yr−1, which is equivalent to 0.5 Tg C yr−1 or 1.8 Mt CO2 yr−1 based on the area of the city (149.81 km2). A network of eddy covariance measurements is a powerful tool to evaluate CO2 emissions from urban areas.

scholarly journals Response Patterns of Vegetation Phenology along Urban-Rural Gradients in Urban Areas of Different Sizes

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-11 ◽  
Author(s):  
Xue Luo ◽  
Yuqing Zhang ◽  
Dongqi Sun
Keyword(s):  
Urban Areas ◽  
Growing Season ◽  
Liaoning Province ◽  
Vegetation Phenology ◽  
Coastal Cities ◽  
Nighttime Light Data ◽  
Urban Rural ◽  
Nighttime Light ◽  
Urban Size ◽  
The Difference

On the basis of MODIS Enhanced Vegetation Index time series data and multisource data, such as nighttime light data and China City Statistical Yearbook data, we investigated the differences in vegetation phenology along urban-rural gradients in urban areas of different sizes between coastal and inland cities in Liaoning Province, China. The results showed that the following: (1) the iterative extraction of urban built-up areas using the threshold method based on nighttime light data combined with the definition of urban built-up areas had high accuracy. (2) Additionally, we found that the start of the growing season (SOS) in Liaoning Province occurred between day 100 and day 180, while the end of the growing season (EOS) occurred between days 260 and 330. The difference in the SOS between coastal cities (i.e., Dalian, Yingkou, Panjin, Jinzhou, Huludao, and Dandong) and inland cities (i.e., Chaoyang, Fuxin, Tieling, Shenyang, Fushun, Liaoyang, Benxi, and Anshan) was 1.70 days. However, the difference in the EOS was more significant, i.e., the EOS in coastal cities occurred 4.47 days later than that in the inland cities. (3) In urban areas of different sizes, the ∆SOS and ∆EOS of inland cities had negative correlations with urban size. Specifically, when the urban size increased 10-fold, the ∆SOS and ∆EOS advanced by 10.03 and 5.71 days, respectively. In contrast, the ∆SOS and ∆EOS of coastal cities had positive and negative correlations with the urban size, respectively. Specifically, when urban size increased 10-fold, ∆SOS was delayed by 11.29 days while EOS was advanced by 8.83 days.

scholarly journals Response of carbon fluxes to water relations in a savanna ecosystem in South Africa

2008 ◽  
Vol 5 (6) ◽  
pp. 1797-1808 ◽  
Author(s):  
W. L. Kutsch ◽  
N. Hanan ◽  
B. Scholes ◽  
I. McHugh ◽  
W. Kubheka ◽  
...  
Keyword(s):  
South Africa ◽  
Water Relations ◽  
Ecosystem Respiration ◽  
Stomatal Closure ◽  
Growing Season ◽  
Carbon Fluxes ◽  
Dry Season ◽  
Canopy Conductance ◽  
Wet Season ◽  
Eddy Covariance Method

Abstract. The principal mechanisms that connect carbon fluxes with water relations in savanna ecosystems were studied by using eddy covariance method in a savanna ecosystem at Kruger National Park, South Africa. Since the annual drought and rewetting cycle is a major factor influencing the function of savanna ecosystems, this work focused on the close inter-connection between water relations and carbon fluxes. Data from a nine-month measuring campaign lasting from the early wet season to the late dry season were used. Total ecosystem respiration showed highest values at the onset of the growing season, a slightly lower plateau during the main part of the growing season and a continuous decrease during the transition towards the dry season. The regulation of canopy conductance was changed in two ways: changes due to phenology during the course of the growing season and short-term acclimation to soil water conditions. The most constant parameter was water use efficiency that was influenced by VPD during the day but the VPD response curve of water usage did change only slightly during the course of the growing season and decreased by about 30% during the transition from wet to dry season. The regulation of canopy conductance and photosynthetic capacity were closely related. This observation meets recent leaf-level findings that stomatal closure triggers down-regulation of Rubisco during drought. Our results may show the effects of these processes on the ecosystem scale.

scholarly journals Surface fluxes and water balance of spatially varying vegetation within a small mountainous headwater catchment

2010 ◽  
Vol 14 (6) ◽  
pp. 965-978 ◽  
Author(s):  
G. N. Flerchinger ◽  
D. Marks ◽  
M. L. Reba ◽  
Q. Yu ◽  
M. S. Seyfried
Keyword(s):  
Water Balance ◽  
Eddy Covariance ◽  
Latent Heat ◽  
Populus Tremuloides ◽  
Growing Season ◽  
Carbon Fluxes ◽  
Surface Fluxes ◽  
Area Index ◽  
Large Variability ◽  
Headwater Catchment

Abstract. Precipitation variability and complex topography often create a mosaic of vegetation communities in mountainous headwater catchments, creating a challenge for measuring and interpreting energy and mass fluxes. Understanding the role of these communities in modulating energy, water and carbon fluxes is critical to quantifying the variability in energy, carbon, and water balances across landscapes. The focus of this paper was: (1) to demonstrate the utility of eddy covariance (EC) systems in estimating the evapotranspiration component of the water balance of complex headwater mountain catchments; and (2) to compare and contrast the seasonal surface energy and carbon fluxes across a headwater catchment characterized by large variability in precipitation and vegetation cover. Eddy covariance systems were used to measure surface fluxes over sagebrush (Artemesia arbuscula and Artemesia tridentada vaseyana), aspen (Populus tremuloides) and the understory of grasses and forbs beneath the aspen canopy. Peak leaf area index of the sagebrush, aspen, and aspen understory was 0.77, 1.35, and 1.20, respectively. The sagebrush and aspen canopies were subject to similar meteorological forces, while the understory of the aspen was sheltered from the wind. Missing periods of measured data were common and made it necessary to extrapolate measured fluxes to the missing periods using a combination of measured and simulated data. Estimated cumulative evapotranspiratation from the sagebrush, aspen trees, and aspen understory were 384 mm, 314 mm and 185 mm. A water balance of the catchment indicated that of the 699 mm of areal average precipitation, 421 mm was lost to evapotranspiration, and 254 mm of streamflow was measured from the catchment; water balance closure for the catchment was within 22 mm. Fluxes of latent heat and carbon for all sites were minimal through the winter. Growing season fluxes of latent heat and carbon were consistently higher above the aspen canopy than from the other sites. While growing season carbon fluxes were very similar for the sagebrush and aspen understory, latent heat fluxes for the sagebrush were consistently higher, likely because it is more exposed to the wind. Sensible heat flux from the aspen tended to be slightly less than the sagebrush site during the growing season when the leaves were actively transpiring, but exceeded that from the sagebrush in May, September and October when the net radiation was not offset by evaporative cooling in the aspen. Results from this study demonstrate the utility of EC systems in closing the water balance of headwater mountain catchments and illustrate the influence of vegetation on the spatial variability of surface fluxes across mountainous rangeland landscapes.

scholarly journals Incorporating grassland management in ORCHIDEE: model description and evaluation at 11 eddy-covariance sites in Europe

2013 ◽  
Vol 6 (6) ◽  
pp. 2165-2181 ◽  
Author(s):  
J. F. Chang ◽  
N. Viovy ◽  
N. Vuichard ◽  
P. Ciais ◽  
T. Wang ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Large Scale ◽  
Management Practices ◽  
Ecosystem Respiration ◽  
Net Ecosystem Exchange ◽  
Grassland Management ◽  
Forage Yield ◽  
Model Description ◽  
Co2 Fluxes ◽  
Area Index

Abstract. This study describes how management of grasslands is included in the Organizing Carbon and Hydrology in Dynamic Ecosystems (ORCHIDEE) process-based ecosystem model designed for large-scale applications, and how management affects modeled grassland–atmosphere CO2 fluxes. The new model, ORCHIDEE-GM (grassland management) is enabled with a management module inspired from a grassland model (PaSim, version 5.0), with two grassland management practices being considered, cutting and grazing. The evaluation of the results from ORCHIDEE compared with those of ORCHIDEE-GM at 11 European sites, equipped with eddy covariance and biometric measurements, shows that ORCHIDEE-GM can realistically capture the cut-induced seasonal variation in biometric variables (LAI: leaf area index; AGB: aboveground biomass) and in CO2 fluxes (GPP: gross primary productivity; TER: total ecosystem respiration; and NEE: net ecosystem exchange). However, improvements at grazing sites are only marginal in ORCHIDEE-GM due to the difficulty in accounting for continuous grazing disturbance and its induced complex animal–vegetation interactions. Both NEE and GPP on monthly to annual timescales can be better simulated in ORCHIDEE-GM than in ORCHIDEE without management. For annual CO2 fluxes, the NEE bias and RMSE (root mean square error) in ORCHIDEE-GM are reduced by 53% and 20%, respectively, compared to ORCHIDEE. ORCHIDEE-GM is capable of modeling the net carbon balance (NBP) of managed temperate grasslands (37 ± 30 gC m−2 yr−1 (P < 0.01) over the 11 sites) because the management module contains provisions to simulate the carbon fluxes of forage yield, herbage consumption, animal respiration and methane emissions.

scholarly journals Response of carbon fluxes to water relations in a savanna ecosystem in South Africa

2008 ◽  
Vol 5 (3) ◽  
pp. 2197-2235 ◽  
Author(s):  
W. L. Kutsch ◽  
N. Hanan ◽  
R. J. Scholes ◽  
I. McHugh ◽  
W. Kubheka ◽  
...  
Keyword(s):  
South Africa ◽  
Water Relations ◽  
Ecosystem Respiration ◽  
Stomatal Closure ◽  
Growing Season ◽  
Carbon Fluxes ◽  
Dry Season ◽  
Canopy Conductance ◽  
Wet Season ◽  
Leaf Level

Abstract. The principal mechanisms that connect carbon fluxes with water relations in savanna ecosystems were studied by using eddy covariance in a savanna ecosystem at Kruger National Park, South Africa. Since the annual drought and rewetting cycle is a major factor influencing the function of savanna ecosystems, this work focused on the close inter-connection between water relations and carbon fluxes. Data from a nine-month measuring campaign lasting from the early wet season to the late dry season were used. Total ecosystem respiration showed highest values at the onset of the growing season, a slightly lower plateau during the main part of the growing season and a continuous decrease during the transition towards the dry season. The regulation of canopy conductance was changed in two ways: changes due to phenology during the course of the growing season and short-term acclimation to soil water conditions. The most constant parameter was water use efficiency that was influenced by VPD during the day but the VPD response curve of water usage did change only slightly during the course of the growing season and decreased by about 30% during the transition from wet to dry season. The regulation of canopy conductance and photosynthetic capacity were closely related. This observation meets recent leaf-level findings that stomatal closure triggers down-regulation of Rubisco during drought. Our results may show the effects of these processes on the ecosystem scale.

scholarly journals Analyzing the causes and spatial pattern of the European 2003 carbon flux anomaly using seven models

2008 ◽  
Vol 5 (2) ◽  
pp. 561-583 ◽  
Author(s):  
M. Vetter ◽  
G. Churkina ◽  
M. Jung ◽  
M. Reichstein ◽  
S. Zaehle ◽  
...  
Keyword(s):  
Central Europe ◽  
Carbon Flux ◽  
Ecosystem Respiration ◽  
Growing Season ◽  
Carbon Fluxes ◽  
Ecosystem Processes ◽  
Total Carbon ◽  
Reference Period ◽  
Process Oriented ◽  
One Year

Abstract. Globally, the year 2003 is associated with one of the largest atmospheric CO2 rises on record. In the same year, Europe experienced an anomalously strong flux of CO2 from the land to the atmosphere associated with an exceptionally dry and hot summer in Western and Central Europe. In this study we analyze the magnitude of this carbon flux anomaly and key driving ecosystem processes using simulations of seven terrestrial ecosystem models of different complexity and types (process-oriented and diagnostic). We address the following questions: (1) how large were deviations in the net European carbon flux in 2003 relative to a short-term baseline (1998–2002) and to longer-term variations in annual fluxes (1980 to 2005), (2) which European regions exhibited the largest changes in carbon fluxes during the growing season 2003, and (3) which ecosystem processes controlled the carbon balance anomaly . In most models the prominence of 2003 anomaly in carbon fluxes declined with lengthening of the reference period from one year to 16 years. The 2003 anomaly for annual net carbon fluxes ranged between 0.35 and –0.63 Pg C for a reference period of one year and between 0.17 and –0.37 Pg C for a reference period of 16 years for the whole Europe. In Western and Central Europe, the anomaly in simulated net ecosystem productivity (NEP) over the growing season in 2003 was outside the 1σ variance bound of the carbon flux anomalies for 1980–2005 in all models. The estimated anomaly in net carbon flux ranged between –42 and –158 Tg C for Western Europe and between 24 and –129 Tg C for Central Europe depending on the model used. All models responded to a dipole pattern of the climate anomaly in 2003. In Western and Central Europe NEP was reduced due to heat and drought. In contrast, lower than normal temperatures and higher air humidity decreased NEP over Northeastern Europe. While models agree on the sign of changes in simulated NEP and gross primary productivity in 2003 over Western and Central Europe, models diverge in the estimates of anomalies in ecosystem respiration. Except for two process models which simulate respiration increase, most models simulated a decrease in ecosystem respiration in 2003. The diagnostic models showed a weaker decrease in ecosystem respiration than the process-oriented models. Based on the multi-model simulations we estimated the total carbon flux anomaly over the 2003 growing season in Europe to range between –0.02 and –0.27 Pg C relative to the net carbon flux in 1998–2002.

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