## 3 Results
### Biogenic CO\({}_{2}\) Fluxes and Anthropogenic CO\({}_{2}\) Emissions in the Greater Tokyo Area  
The spatial distribution of anthropogenic CO\({}_{2}\) emissions and biogenic CO\({}_{2}\) fluxes in the Greater Tokyo Area barely overlapped and exhibited some asynchronous characteristics, as the examples of our modeling results in Figures 4, 5 and 9 demonstrate. On one hand, Tokyo was surrounded by evergreen and deciduous forests in Ibaraki, Chiba, Saitama, and Kanagawa prefectures, which were sources of biogenic CO\({}_{2}\). On the other hand, strong anthropogenic CO\({}_{2}\) emissions occurred from the Tokyo metropolis, as well as from the Keith and Keiyou industrial areas near Tokyo and the Kashima seaside industrial area (marked by dashed cycles in Figure 1, respectively), where power plants and factories are concentrated. If the range of the biogenic CO\({}_{2}\) flux in our study area was much smaller than that of anthropogenic CO\({}_{2}\) emissions, then neglecting the former in a top-down approach modeling would not cause much error in back-casting results. Otherwise, accurate calculation of the biogenic CO\({}_{2}\) flux is essential for updating the anthropogenic CO\({}_{2}\) emission inventory in the megacity of Tokyo. The comparisons of hourly integrated _GPP_ (photosynthetic CO\({}_{2}\) uptake), \(R_{e}\) (biogenic CO\({}_{2}\) emission), and \(NEE\) (net biogenic CO\({}_{2}\)  
Figure 8: Regional variation example of **(a)** modeled annual _NPP_ and **(b)** difference between modeled and MODIS (MOD17A3 HGF) annual _NPP_ in 2018; the average **(c)** and standard deviations **(d)** of the difference between modeled and MODIS (MOD17A3 HGF) annual _NPP_ during the period 2010–2018. flux) to hourly anthropogenic CO\({}_{2}\) emissions in the Greater Tokyo Area (Figure 10) provide some reference to evaluate this question. For our study, \"hourly integrated\" refers to the sum of modeled results in all grid cells within 139\({}^{\circ}\)E-141\({}^{\circ}\)E, 35\({}^{\circ}\)N-36.33\({}^{\circ}\)N, averaged over all days in each month during the period 2010-2018. The mean and standard deviation of hourly integrated biogenic CO\({}_{2}\) fluxes are elaborated as below. To elaborate, first, hourly integrated anthropogenic CO\({}_{2}\) emissions of the Greater Tokyo Area presented similar diurnal variations year-round; the lowest level (2.37-2.64 \(\times\) 10\({}^{4}\) ton CO\({}_{2}\) h\({}^{-1}\)) was found after midnight when human activities were least active. As traffic rush hours started in the morning, hourly integrated anthropogenic CO\({}_{2}\) emissions increased gradually and almost doubled by around 9 a.m. to 4.05-4.63 \(\times\) 10\({}^{4}\) ton CO\({}_{2}\) h\({}^{-1}\). From then until late afternoon, the integrated anthropogenic CO\({}_{2}\) emissions entered a plateau phase and then started to drop at about 8 pm, after the evening traffic rush hours. Secondly, the hourly integrated biogenic CO\({}_{2}\) emissions of the Greater Tokyo Area, the total of vegetation-respired CO\({}_{2}\) and CO\({}_{2}\) emitted via \(SOC\) decomposition processes, exhibited both sub-daily and seasonal variations. At night, the lowest hourly integrated biogenic CO\({}_{2}\) emissions (0.09 \(\pm\) 0.01 \(\times\) 10\({}^{4}\) ton CO\({}_{2}\) h\({}^{-1}\)), which was about 3.07 \(\pm\) 0.51% of the hourly integrated anthropogenic CO\({}_{2}\) emission in the area, occurred at 4 a.m. in January. In the daytime, the hourly integrated biogenic CO\({}_{2}\) emissions became stronger and peaked in the early afternoon (around 3 p.m.). The peak biogenic CO\({}_{2}\) emission (0.16 \(\pm\) 0.03 \(\times\) 10\({}^{4}\) ton CO\({}_{2}\) h\({}^{-1}\)) was equivalent to about 3.55 \(\pm\) 0.79% of the hourly integrated anthropogenic CO\({}_{2}\) emissions in January. Such a rise in integrated biogenic CO\({}_{2}\) emissions was probably attributable to increased temperatures and additional vegetation growth respiration when photosynthesis was active during the day.