Urban microclimate and outdoor thermal comfort. A proper procedure to fit ENVI-met simulation outputs to experimental data

• A proper procedure for numerical simulations with the software ENVI-met.
• Right choice and determination of input parameters for simulations.
• Experimental measures of microclimatic variables and thermal perception in an outdoor area.
• Comparison between the ENVI-met outputs and the values measured experimentally.
• The mean deviation is of about 1% for air and mean radiant temperature and of about 0.76 units for the PMV.

This paper, while referring to a case study, focuses on the assessment of the input parameters based on the equations solved by ENVI-met. The output data of different micrometeorological variables and Predicted Mean Vote (PMV) were compared to the experimental values measured on the field in different points and for several days. The results provided by the software were examined while taking into consideration a different cell size of the mesh as well. However significant differences were not recognized and the 2 × 2 m2 cell-sized model was chosen; it represents a good compromise for what concerns results’ accuracy and computation time. This gave the possibility to determine a deviation of 0.6% for air temperature, 0.9% for mean radiant temperature, about 2.0% for relative humidity and about 10% for global radiation. The predictive ability of the software was also testified, for air temperature and mean radiant temperature, by the analysis of the coefficient of determination, Root Mean Square Error and Willmott’s index of agreement. Then the PMV values were compared with those measured during a field survey with an average deviation of 0.76 units and it was possible to determine how, among the different Lateral Boundary Conditions (LBC), the open type leads to more reliable results. Finally the latest version of the software was tested and in the conclusions a general procedure to perform simulations in ENVI-met is suggested.