Impact of land use and soil moisture on partition of turbulent heat fluxes

The knowledge of atmosphere-surface interactions is important to improve living and environmental conditions. Land use and soil moisture are two main factors that influence the partition of turbulent heat fluxes. The objective of this study is to quantify especially the latent heat transport in areas with various types of urban land use (vegetated vs. non-vegetated) in respect to seasonal and diurnal variations, aiming to improve thermal comfort in the context of predicted climate change. For this purpose eddy-covariance technique has been carried out in an urban-suburban area (Oberhausen Germany; 51° N, 6° E, 15 August 2010 and 14 August 2011).

The results show that sensible heat flux (Q_H) is 20 % higher, latent heat flux (Q_E) 90 % lower at the highly sealed site compared to the vegetated one. Furthermore, it could be shown, that the partition of Q_H is an exponential function of the plan area density, whereas the Q_E is a linear function. With increasing fraction of sealed area the Q_H increased, while Q_E decreased. So, a high fraction of vegetated areas within an impervious terrain can counteract growing thermal stress on city-dwellers, demonstrating by the human-biometeorological thermal index (here: physiologically equivalent temperature, PET). But, if the soil moisture decreased during longer periods of drought the monthly average Q_E value decreased by 50 % and this positive thermal effect is therefore reduced or entirely lost.

The paper discussed the impact of land use and soil moisture on energy partition before the backdrop of global climate change mitigation procedures.