How should the anthropogenic heat be treated in the urban surface energy balance: revisit of the definition of QF
- 1School of Science and Engineering, Meisei University, Hino City, Tokyo, Japan (kikegawa@es.meisei-u.ac.jp)
- 2Department of Earth and Ocean Sciences, National Defense Academy of Japan, Yokosuka City, Kanagawa, Japan (hirofumisugawara@gmail.com)
- 3Meteorological Engineering Center, Inc., Osaka City, Osaka, Japan (21mb004@stu.meisei-u.ac.jp)
The most widely accepted concept of energy balance in the volume of the urban canopy layer is expressed by the following equation,
Q* + QF = QH + QE + ΔQS + ΔQA
where Q* is the net all-wave radiation, QF the anthropogenic heat flux, QH the turbulent sensible heat flux, QE the latent heat flux, ΔQS the net storage heat flux and ΔQA the net advective heat flux.
Through observations and simulations targeting a residential area in Tokyo, this study proposes revisions to the above conventional concept for energy balance in the following two respects.
1. QF should be interpreted not as the anthropogenic exhaust heat released to the urban atmosphere but as energetic bulk input to the urban canopy where QF is equivalent to heat resulting from fuels combustion and electricity consumption with usually negligible metabolic heat there.
2. Instead, actual anthropogenic exhaust heat should be treated as components of the turbulent heat fluxes (QH and QE) using the following equation,
QH = QHb + QHt + QHs
where QHb is the net building anthropogenic heat consisting of waste heat from HAC (heating and air conditioning) systems and exchanged heat between indoors and outdoors through ventilation, QHt the anthropogenic heat from traffic and QHs the turbulent sensible heat flux (convection) from the urban surfaces. The same concept holds true for the latent heat.
The above revisions are applied in this study to the full energy flow analysis for the residential urban canopy in Tokyo using the eddy covariance CO2 flux and O2 & CO2 concentrations measurements, together with fine resolution (time and space) inventory data of electricity use and car traffic. Through the analysis, we estimate QF by source (electricity, liquid and gas fuel) and each component of the turbulent heat fluxes (QHb, QHt and QHs). Finally, those observation-based estimates are compared with the simulations with a focus on QHb. The authors’ multi-layer urban canopy model coupled with the building energy model is used for the simulations. Resultantly, observation-based components of urban energy balance show good agreement with those from simulations including QHb, suggesting the validity of the authors’ revisions to the conventional urban surface energy balance concept.
How to cite: Kikegawa, Y., Sugawara, H., Kobayashi, T., and Maruyama, N.: How should the anthropogenic heat be treated in the urban surface energy balance: revisit of the definition of QF, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-245, https://doi.org/10.5194/ems2024-245, 2024.
