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For low wind speeds (2 and 4 m/s), after the sensors were moved a distance beyond the boundary layer thickness as predicted by Eq. (3), the air temperature readings still showed a downward trend; thus we assumed that free flow temperature was not yet attained. Such behavior of the air temperature was more notorious with the horizontal concrete wall and a 2 m/s airflow because even at the highest possible vertical displacement of the sensors system (0.0078 mm), the sensor readings still showed a slight downward trend; therefore, we were not able to measuring the boundary layer thickness because of the design limitations of our system. Fig. 6 shows an example of this case for a horizontal concrete wall and a 4 m/s wind velocity. The free flow temperature is reached, but this measurement is shifted some millimeters beyond that predicted by Eq. (3).