O<sub>2</sub> : CO<sub>2</sub> exchange ratio for net turbulent flux observed in an urban area of Tokyo, Japan, and its application to an evaluation of anthropogenic CO<sub>2</sub> emissions
oleh: S. Ishidoya, H. Sugawara, Y. Terao, N. Kaneyasu, N. Aoki, K. Tsuboi, H. Kondo
| Format: | Article |
|---|---|
| Diterbitkan: | Copernicus Publications 2020-05-01 |
Deskripsi
<p>In order to examine <span class="inline-formula">O<sub>2</sub></span> consumption and <span class="inline-formula">CO<sub>2</sub></span> emission in a megacity, continuous observations of atmospheric <span class="inline-formula">O<sub>2</sub></span> and <span class="inline-formula">CO<sub>2</sub></span> concentrations, along with <span class="inline-formula">CO<sub>2</sub></span> flux, have been carried out simultaneously since March 2016 at the Yoyogi (YYG) site located in the middle of Tokyo, Japan. An average <span class="inline-formula">O<sub>2</sub> : CO<sub>2</sub></span> exchange ratio for net turbulent <span class="inline-formula">O<sub>2</sub></span> and <span class="inline-formula">CO<sub>2</sub></span> fluxes (OR<span class="inline-formula"><sub>F</sub></span>) between the urban area and the overlaying atmosphere was obtained based on an aerodynamic method using the observed <span class="inline-formula">O<sub>2</sub></span> and <span class="inline-formula">CO<sub>2</sub></span> concentrations. The yearly mean OR<span class="inline-formula"><sub>F</sub></span> was found to be 1.62, falling within the range of the average OR values of liquid and gas fuels, and the annual average daily mean <span class="inline-formula">O<sub>2</sub></span> flux at YYG was estimated to be <span class="inline-formula">−16.3</span> <span class="inline-formula">µ</span>mol m<span class="inline-formula"><sup>−2</sup></span> s<span class="inline-formula"><sup>−1</sup></span> based on the OR<span class="inline-formula"><sub>F</sub></span> and <span class="inline-formula">CO<sub>2</sub></span> flux. By using the observed OR<span class="inline-formula"><sub>F</sub></span> and <span class="inline-formula">CO<sub>2</sub></span> flux, along with the inventory-based <span class="inline-formula">CO<sub>2</sub></span> emission from human respiration, we estimated the average diurnal cycles of <span class="inline-formula">CO<sub>2</sub></span> fluxes from gas and liquid fuel consumption separately for each season. Both the estimated and inventory-based <span class="inline-formula">CO<sub>2</sub></span> fluxes from gas fuel consumption showed average diurnal cycles with two peaks, one in the morning and another one in the evening; however, the evening peak of the inventory-based gas consumption was much larger than that estimated from the <span class="inline-formula">CO<sub>2</sub></span> flux. This can explain the discrepancy between the observed and inventory-based total <span class="inline-formula">CO<sub>2</sub></span> fluxes at YYG. Therefore, simultaneous observations of OR<span class="inline-formula"><sub>F</sub></span> and <span class="inline-formula">CO<sub>2</sub></span> flux are useful in validating <span class="inline-formula">CO<sub>2</sub></span> emission inventories from statistical data.</p>