The Green CTTC model for predicting the air temperature in small urban wooded sites

An analytical model, the Green CTTC (cluster thermal time constant) model, for predicting diurnal air temperature inside an urban wooded site, is the object of this study. The proposed model is based on the same principles as the CTTC model, developed earlier by M.E. Hoffman and colleagues, with the addition of vegetation effects. It is shown that the tree thermal effect can be evaluated either as the shade effect partly offset by the convection component of the tree radiation balance or, equivalently, as the combined effect of evapotranspiration and the change in the plant heat storage. In this paper, the former approach is adopted. Simulations for testing the validity of the Green CTTC model were carried out on summer data of 11 small urban wooded sites in the Tel-Aviv metropolitan area near the Mediterranean sea coast. Results show a satisfactory fit, with average root-mean-square-error <0.5 K for all studied sites and time intervals at 09:00, 15:00, and 18:00 h (summer time). The CTTC values and the convection parameters were estimated from the empirical data, using a novel procedure. The proposed model, which can be enlarged to encompass the cases of groves and lawns, is an appropriate tool for assessment of the climatic impact of trees and other greeneries on urban design alternatives.