Date of Award

Summer 8-1-2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Coastal and Marine Systems Science

College

College of Science

First Advisor

Erin E. Hackett

Second Advisor

Diane Fribance

Third Advisor

Craig Gilman

Additional Advisors

Anne Fullerton; Roberto Padilla-Hernandez

Abstract

Large knowledge gaps concerning the effect of ocean surface waves on near-surface vertical distributions of temperature and humidity in the marine atmospheric surface layer exist due to practical limitations and sensor fidelity challenges of direct measurements. Wave effects on these distributions between the wave trough and crest are least studied within the literature. These scalar distributions influence atmospheric refractivity, which can lead to anomalous propagation of electromagnetic energy. Measurements of temperature and humidity are classically made using rocket- or radiosondes and fixed weather stations, and can utilize tethered profiling systems. However, these measurement systems have limitations when obtaining measurements near the sea surface. Consequently, boundary layer similarity models (i.e., Monin Obuhkov (MO) theory) are commonly employed to fill in these near-surface measurement gaps despite the documented shortcomings of these models in this region. To address this observational gap, this research develops a novel near-surface wave-coherent instantaneous profiling system (NWIPS) to aid in enriching our current knowledge regarding the influence of waves on near-surface vertical scalar distributions. Eighty minutes of wave-coherent instantaneous vertical scalar distributions were measured by NWIPS in an unstable atmosphere. It is the first attempt to obtain high resolution, wave-coherent vertical distributions of temperature and humidity within the lowest 3 m of altitude. Utilizing these measurements, the variability of near-surface vertical scalar distributions is investigated. These results are discussed in the context of their impact on propagation loss predictions for X-band and K-band frequencies.

Comparisons between classical MO theory profiles and NWIPS measured profiles showed disagreement below 4 m, whereas above this altitude, there was good agreement. Comparisons between PL predictions for the two refractivity profiles revealed lower propagation loss at long range for MO theory, and differences are most significant for K-band. Below 4 m, distinct, persistent, vertical structure in both ten-minute and 80-minute ensembles and 80-minute wave phase-averaged vertical scalar profiles were observed. The complex structure in the mean temperature vertical distribution near the surface is consistent with prior laboratory and numerical studies. Variations in refractivity over wave phase showed the primary difference between refractivity profiles at the crest, trough, upslope, and downslope was the vertical shifting of the profiles resulting from the shifting surface. The phase-averaged profiles were also found to be steady over the 80-minute experiment consistent with the similar wave conditions during this time. The differences in the refractivity profiles for the various wave phases are shown to be relatively insignificant to X-band propagation predictions, while for K-band some discrepancies are observed over both flat and wavy surfaces. The differences resulting from the duct height shifting in range and/or the introduction of a wavy surface causes larger differences in propagation predictions than do changes in the refractivity profile with phase.

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