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Keywords:

  • urban energy balance;
  • storage heat flux;
  • anthropogenic heat flux

Abstract

The role of net heat storage ΔQS and anthropogenic heat QF are considered in the surface energy balance for a downtown area in Łódź, 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 ΔQS based on representative surface temperature sampling is employed and compared with results from two other models. Results show that ΔQS 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 ΔQS estimates over hourly intervals, QF was then determined as the residual of the energy balance. Using the approach, QF 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 ΔQS and variation in QF. Results highlight the need for future investigations of the urban surface energy balance to incorporate more complete measurements and estimates of ΔQS. Copyright © 2005 Royal Meteorological Society.