Diurnal Variation of CO&lt;sub&gt;2&lt;/sub&gt; Flux in an Urban Area of Tokyo

Hirano, Tatsuki; Sugawara, Hirofumi; Murayama, Shohei; Kumakura, Hiroaki

doi:10.2151/sola.2015-024

Cited by 22 publications

(20 citation statements)

References 23 publications

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“…2a) may contribute to lower emissions as a result of reduced building heating and thus lower annual emissions in Sakai City compared with other northern cities. The annual emissions rate in our urban center was comparable to that of the densely populated residential areas in Yoyogi, Tokyo (4.3 kg C m −2 yr −1 ; Hirano et al, 2015), and Figure 10. Spatial distributions of (a) the green fraction and (b) the upscaled net CO 2 flux in Sakai City.…”

Section: Discussionsupporting

confidence: 56%

“…8), representing the strength of human activities. Previous urban CO 2 flux studies have reported that major contributors to anthropogenic emissions were vehicle emissions and gas consumption (Gioli et al, 2012;Hirano et al, 2015;Velasco et al, 2005;Ward et al, 2013). Velasco and Roth (2010) indicated that weekly cycles were primarily related to vehicle emissions.…”

Section: Discussionmentioning

confidence: 99%

“…4, 6, 9). The approach was previously used for clarifying variations in fluxes in different landscapes involved single flux measurements Kordowski and Kuttler, 2010;Hirano et al, 2015). The partitioning concurrently contained the limitations in which data availability decreases with par-titioning.…”

Section: Discussionmentioning

confidence: 99%

“…To evaluate CO 2 emissions in cities and their temporal and spatial variabilities, continuous measurements of CO 2 fluxes have been conducted using the eddy covariance method in various urban landscapes in several cities, including dense urban built-up areas (Gioli et al, 2012;Grimmond et al, 2002Grimmond et al, , 2004Kotthaus and Grimmond, 2012;Nimitz et al, 2002;Pawlak et al, 2011;Velasco et al, 2005), suburban areas (Bergeron and Strachan, 2011;Coutts et al, 2007;Crawford et al, 2011;Hirano et al, 2015;Moriwaki et al, 2006;Ward et al, 2013), urban parks (Kordowski and Kuttler, 2010), and urban forests (Awal et al, 2010). These results have indicated that cities emits a considerable amount of CO 2 into the atmosphere from human activities, such as vehicle traffic and household heating in the wintertime.…”

Section: Introductionmentioning

confidence: 99%

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

Ueyama

Ando

2016

Atmos. Chem. Phys.

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Abstract. To evaluate CO 2 emissions in urban areas and their temporal and spatial variability, continuous measurements of CO 2 fluxes were conducted using the eddy covariance method at three locations in Sakai, Osaka, Japan. Based on the flux footprint at the measurement sites, CO 2 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. A distinct biological uptake of CO 2 was observed in the suburb, urban park, and rural areas in the daytime, whereas high emissions were observed in the dense and moderate urban areas in the daytime. Weekday CO 2 emissions in the dense urban center and suburban area were approximately 50 % greater than emissions during weekends 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 photosynthetic uptake, exhibiting the lowest daily emissions or even uptake during the summer months. In contrast, the dense and moderately urban areas emitted CO 2 in all seasons. CO 2 emissions in the urban areas were high in the winter and summer months, and they significantly increased with the increase in air temperature in the summer and the decrease in air temperature in the winter. Irrespective of the land cover type, all urban landscapes measured in this study acted as net annual CO 2 sources, with emissions ranging from 0.5 to 4.9 kg C m −2 yr −1 . The magnitude of the annual CO 2 emissions was negatively correlated with the green fraction; areas with a smaller green fraction had higher annual CO 2 emissions. Upscaled flux estimated 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 CO 2 yr −1 , based on the area of the city (149.81 km 2 ).A network of eddy covariance measurements is useful for characterizing the spatial and temporal variations in net CO 2 fluxes from urban areas. Multiple methods would be required to evaluate the rationale behind the fluxes and overcome the limitations in the future.

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Section: Discussionsupporting

confidence: 56%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Ueyama

Ando

2016

Atmos. Chem. Phys.

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“…Many studies have been made to characterize the CO 2 concentration or flux in areas of various types classified in the same way as we described as a result of this study [5,[19][20][21][22][23][24][25][26][27][28][29][30]. Many of them are made based on CO 2 flux measurements using the eddy covariance method, which analyze CO 2 concentration data measured with a high response speed system and three-dimensional wind data measured by a ultrasonic anemometer assuming that the vertical gradient of CO 2 concentration is proportional to CO 2 flux from the surface.…”

Section: Discussionmentioning

confidence: 99%

Diurnal and Seasonal Variations of Carbon Dioxide (CO2) Concentration in Urban, Suburban, and Rural Areas around Tokyo

Imasu

Tanabe

2018

Atmosphere

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Site environments and instrumental characteristics of carbon dioxide (CO 2 ) measurements operated by local governments in the Kanto Plain, the center of which is Tokyo, were summarized for this study. The observation sites were classified into environments of three types: urban, suburban, and woodland. Based on a few decades of accumulated hourly data, the diurnal and seasonal variations of CO 2 concentrations were analyzed as a composite of anomalies from annual means recorded for each site. In urban areas, the highest concentrations appear before midnight in winter. The second peak corresponds to the morning rush hour and the strengthening of the inversion layer. Suburban areas can be characterized as having the highest concentration before dawn and the lowest concentration during the daytime in summer in association with the activation of respiration and photosynthesis of vegetation. In these areas, concentration peaks also appear during the morning rush hour. Woodland areas show background features, with the highest concentration in early spring, which are higher than the global background by about 5 ppmv.Atmosphere 2018, 9, 367 2 of 10 digital format to researchers for the region. Based on data observed during more than a decade, the diurnal and seasonal variations of CO 2 concentrations were analyzed to characterize site environments.

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