Heat storage and anthropogenic heat flux in relation to the energy balance of a central European city centre

The role of net heat storage Delta Q(S) and anthropogenic heat Q(F) are considered in the surface energy balance for a downtown area in Lodz, Poland, for a 2 year period. Eddy covariance measurements provide estimates of the turbulent heat fluxes and radiometric measurements of the net all-wave radiation. A method to determine Delta Q(S) based on representative surface temperature sampling is employed and compared with results from two other models. Results show that Delta Q(S) is an important flux on the scale of hours to days and that it can be more than 10 W m(-2), on average, for periods of a week or more. By incorporating Delta Q(S) estimates over hourly intervals, Q(F) was then determined as the residual of the energy balance. Using the approach, Q(F) averaged 32 W m(-2) from October to March (60% of available energy), and -3 W m(-2) from June to August. The physically unrealistic negative values for the summer period may suggest underestimation of turbulent fluxes, but no causal factor was identified. Although energy balance closure was close to 100% throughout the year, there was weaker agreement in the winter. This is attributed to errors in estimates of Delta Q(S) and variation in Q(F). Results highlight the need for future investigations of the urban surface energy balance to incorporate more complete measurements and estimates of Delta Q(S). Copyright (c) 2005 Royal Meteorological Society.