Air temperature profiling over different littoral surfaces

Factors that must be considered in the study of long-range atmospheric sound propagation include surface characteristics like ground geometry and surface impedance, as well as air characteristics like wind speed and air temperature profiles. This work presents measurements of air temperature profiles over various surfaces. Such measurements can enable more realistic case assumptions to be made in atmospheric acoustic transmission loss models. Accurate air temperature profiles are critical because of the potentially significant impact on the transmission loss predictions. The main objective of this experiment was capturing the diurnal trends in air temperature profiles over different ground surfaces. The secondary objective was to evaluate a boat-based approach for measuring air temperature profiles over water. Ground surfaces included marsh grass, lawn grass, gravel, and asphalt. Air temperature was measured at every meter up to 7 m elevation. This study highlights the influence of wind speed on the development of temperature inversions. The strength of the inversion was observed to decrease with wind speed for values between 2 and 4 m/s. Strong temperature inversions were not observed at wind speeds greater than approximately 4 m/s. Negative temperature gradients were observed either to decrease slightly or remain unaffected with increased wind speed.