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Crown volume is defined as the geometric space occupied by the crown. Crown volume and the change (growth) of crown volume over time can be an important part of multi-temporal forest analyses but is expensive and time consuming to obtain through conventional forest survey methods for large, remote areas. LiDAR-derived crown volume growth was compared to an expected amount of crown volume growth for 220 Douglasir trees in the Panther Creek, Oregon watershed. A paired t-test between expected crown volume growth and the LiDAR-derived crown volume growth resulted in a p-value of 0.85. Regression procedures between expected crown volume and LiDAR-derived crown volume in 2008 and 2012 resulted in R2 values of 0.45 and 0.53, respectively. LiDAR measured change in crown volume over time was not significantly different than the expected amount of change. With further research, multi-temporal LiDAR could become a viable tool for forest analyses.

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This dissertation describes the design, fabrication and deployment of the Compact Microwave Radiometer for Humidity profiling (CMR-H). The CMR-H is a new and innovative spectrometer radiometer that is based on monolithic microwave and millimeter-wave integrated circuit (MMIC) technology and is designed for tropospheric water vapor profiling. The CMR-H simultaneously measures microwave emission at four optimally-selected frequency channels near the 22.235 GHz water vapor absorption line, constituting a new set of frequencies for the retrieval of the water vapor profile. State-of-the-art water vapor radiometers either measure at additional channels with redundant information or perform multi-frequency measurements sequentially. The fabrication of the CMR-H demonstrates the capability of MMIC technology to reduce substantially the operational power consumption and size of the RF and IF sections. Those sections comprise much of the mass and volume of current microwave receivers for remote sensing, except in the case of large antennas. The use of the compact box-horn array antenna in the CMR-H demonstrates its capability to reduce the mass and volume of microwave radiometers, while maintaining similar performance to that of commonly-used, bulky horn antennas. Due to its low mass, low volume, low power consumption, fabrication complexity and cost, the CMR-H represents a technological improvement in the design of microwave radiometers for atmospheric water vapor observations. The field test and validation of the CMR-H described in this work focuses on comparisons of measurements during two field experiments from the CMR-H and a state-of-the-art microwave radiometer, which measures only in a volume subtended by the zenith-pointing antenna's beam pattern. In contrast, the CMR-H is designed to perform volumetric scans and to function correctly as a node in a network of radiometers. Mass production of radiometers based on the CMR-H design is expected to enable the implementation of a dense network of radiometers designed to perform measurements of the 3-D water vapor field, with the potential to improve weather forecasting, particularly the location and timing of the initiation of intense convective activity responsible for potentially damaging winds, rain, hail and lightning.

When an optical wave propagates through atmosphere, the wave experiences amplitude, phase, and angle-of-arrival (AOA) fluctuations which are mainly caused by the refractive-index fluctuations of the atmosphere. Thus, the wave fluctuations carry characteristics of the atmosphere. In this dissertation, the AOA fluctuations are studied theoretically and experimentally. For the theoretical part, closed-form solutions of the AOA fluctuations for plane and spherical waves observed by a receiver with a finite aperture were developed. It was assumed that the waves propagate through homogeneous and isotropic media and that the Rytov approximation is valid. The existing closed-form solutions of the AOA fluctuations for the waves are valid only for the cases that the aperture size of the receiver is much larger or much smaller than the Fresnel length. The closed-form solutions developed in this dissertation, however, are valid for all ratios between the aperture diameter and the Fresnel length. The closed-form solutions were compared with the numerical solutions and the accuracy of the closed-form solutions is less than 0.2%. For the experimental part, remote sensing of wind speed transverse to a propagation path using the frequency spectra of the AOA fluctuations was performed with a telescope and a CCD camera. The knee frequency, the intersection of the -2/3 and -8/3 power laws of the spectrum, is a function of wind speed and an effective baseline. If the knee frequency and the effective baseline are known, the transverse wind speed can be retrieved, and if the knee frequency and the transverse wind speed are known, the effective baseline can be estimated. From the measured knee frequency of the spectra of the AOA fluctuations and the aperture size of the telescope as initial guess for the effective baseline, the path-averaged transverse wind speed was retrieved. The effective baseline was calibrated based on wind speed measured by a anemometer. The rms difference between the path-averaged calibrated wind speed retrieved from the frequency spectra of the AOA fluctuations with 30 s of estimation time and the 30 s time-averaged transverse wind speed measured by the anemometer was 11 cm/s -1, while the wind speed varied between 0 and 80cm/s-1.

Thesis advisor: Noah Snyder / The dynamics of river suspended sediment, derived from soil erosion, is critical for understanding floodplain and coastal wetland evolution, as well as reservoir sedimentation. Although the U.S. Geological Survey (USGS) has collected > 105 suspended sediment concentration (SSC) samples, data availability is often sparse or altogether lacking for large river transects. Landsat derived SSC measurements have proven accurate enough to supplement USGS datasets, allowing unprecedented spatial analysis of SSC trends throughout large river systems (Dethier et al. 2020). Here, I build on this approach by applying it to higher spatial and temporal resolution datasets. I have derived suspended sediment concentrations from the Sentinel-2 satellite sensor through a cluster and regression approach. To increase the number of training samples, I constructed SSC-discharge rating curves for all in-situ USGS stations. This has constrained the uncertainty of Sentinel-2 derived SSC to less than a factor of two, which has proven adequate for large rivers. In combination with the Landsat record, this allows for a multi-decadal analysis of sediment transport dynamics across multi-dammed systems. This study applies these methods to the Chattahoochee River in Georgia and Alabama, USA. Using observations from 1984 to 2022, there exists pronounced decreases in SSC downstream of dams along the river, with downstream reaches never regaining the same values as upstream observations. Also evident is a decreasing trend in SSC temporally, which could be indicative of changing land-use practices. Code for this project is publicly available at github.com/ivalencius/sentinel-ssc. / Thesis (BA) — Boston College, 2023. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Scholar of the College. / Discipline: Earth and Environmental Sciences.