The importance of the anthropogenic heat flux for simulating the sensible and latent heat fluxes in an urban environment

The first international urban land surface model comparison concluded that models which neglected the anthropogenic heat flux in their surface energy balance performed at least as well as the models that did include a representation of this term. However, as this term supplies additional energy for the other fluxes within the energy balance, it was concluded that further investigation was required to understand these results.

In this study we have used a couple of versions of the JULES model (a model that performed well in the comparison) to investigate the impact of the anthropogenic heat flux. This model originally neglected the term within its simulations, so provides as opportunity to assess the impact on the results from including the flux. The anthropogenic heat flux has been represented in the model in a variety of ways based on different averaging assumptions, in order to assess the impact of both including the flux, and having temporal variations. The methodologies include an average flux applied at every timestep over the whole simulation, a mean diurnal cycle applied to each day of the simulation, a monthly mean flux with the values for each month being applied at every timestep, and a diurnally varying monthly mean flux. The latter includes the full temporal variations from the observational dataset.

The results from each of the simulations will be presented and compared to the original simulations that neglected the anthropogenic heat flux. From these results, conclusions will be drawn on the importance of including the anthropogenic heat flux, having temporal variations in this flux, and the results from the urban comparison will be put into context.