Annual fluxes of energy and CO2 over a residential area in Tokyo

The fluxes of energy and CO₂ were measured for 1 year over a residential area in Tokyo, Japan. The contributions from garden trees, concrete materials, traffic, home heating, and human bodily emissions to the fluxes of latent heat and CO₂ were also investigated. The latent heat flux in the daytime during the summer reached about 180 W m^-2. This large value is likely due to the vegetation and bare soil, which, despite their small areal fraction, have significant evaporation because they are surrounded by hot and dry atmosphere. Net CO₂ was transferred from the surface to the atmosphere. The dominant emissions of CO₂ were attributed to vehicles, human activities, and the exhalations of humans. The magnitude of the CO₂ flux in winter was larger than that during summer, probably because of the uptake of CO₂ by vegetation in summer and the larger emission from houses during winter due to the greater heating. The annual total evaporation E was 228 mm. The precipitation is enough to keep the surface wet but 80% of the precipitation runs off. This is a feature of the water budget in urban areas with a sewer system and having a surface that is covered with impervious materials (buildings and pavements). The annual total CO₂ flux was 3352 gC m^-2 yr^-1. This value is equivalent to negative six times of that from a temperate deciduous forest.