Influence of Sensor Configuration on Measurements of Dry and Wet Bulb Temperature Fluctuations

Abstract

Measurements of dry and wet bulb temperature fluctuations in the atmospheric boundary layer are often accomplished with sensors consisting of a relatively long resistance wire mounted on some kind of supporting frame. It is demonstrated that such a frame may product distortion of temperature fluctuations on a scale as large as 103 times the typical dimensions of the supporting structure. The mechanism for this phenomenon is not evident. It is further demonstrated that the distortion error can be entirely removed if the sensor is constructed so that there is no physical obstruction to the flow through the sensor area. The modified sensors have been used in a recent field experiment. Analysis of the inertial subrange constant ? for the temperature spectrum based on these data yield ? = 0.80 ± 0.09, in good agreement with other recent observations.