Matthew Kehrli

A semi-analytical model is developed for estimating the spectral diffuse attenuation coefficient of downwelling irradiance (Kd(λ)) in inland and coastal waters. The model works as a function of the inherent optical properties (absorption and backscattering), depth, and solar zenith angle. Results of this model are validated using a large number of in-situ measurements of Kd(λ) in clear oceanic, turbid coastal and productive lagoon waters. To further evaluate its relative performance, Kd(λ) values obtained from this model are compared with results from three existing models. Validation results show that the present model is a better descriptor of Kd(λ) and shows an overall better performance compared to the existing models. The applicability of the present model is further tested on two Hyperspectral Imager for the Coastal Ocean (HICO) remote sensing images acquired simultaneously with our field measurements. The …

Extending the capabilities of optical remote sensing and inverse optical algorithms, which have been commonly focused on the visible (VIS) range of the electromagnetic spectrum, to derive the optical properties of seawater in the ultraviolet (UV) range is important to advancing the understanding of various optical, biological, and photochemical processes in the ocean. In particular, existing remote-sensing reflectance models that derive the total spectral absorption coefficient of seawater, a(λ), and absorption partitioning models that partition a(λ) into the component absorption coefficients of phytoplankton, a_ph(λ), non-algal (depigmented) particles, a_d(λ), and chromophoric dissolved organic matter (CDOM), a_g(λ), are restricted to the VIS range. We assembled a quality-controlled development dataset of hyperspectral measurements of a_g(λ) (N = 1294) and a_d(λ) (N = 409) spanning a wide range of values …

In response to the growing interest in offshore wind energy development in California, the U.S. Bureau of Ocean Energy Management delineated three Call Areas for potential leasing. This study provides a comprehensive characterization and comparison of offshore wind power potential within the two Central California Call Areas (Diablo Canyon and Morro Bay) using 12‐ and 15‐MW turbines under different inter‐turbine spacing and wind farm size scenarios. Our analysis shows similar daily and seasonal patterns of wind power produced within the Call Areas, which peak in spring and during evening hours. Per‐turbine power production is higher in the Morro Bay Call Area due to slightly higher hub‐height wind speeds, whereas total power production is higher in the Diablo Canyon Call Area due to its larger size. Turbine type had a negligible impact on average power production per‐unit‐area because while …

In 2019, the Research and Education Collaborative Occultation Network (RECON) obtained multiple-chord occultation measurements of two Centaur objects: 2014 YY 49 on 2019 January 28 and 2013 NL 24 on 2019 September 4. RECON is a citizen-science telescope network designed to observe high-uncertainty occultations by outer solar system objects. Adopting circular models for the object profiles, we derive a radius

Context We present results from the first recorded stellar occultation by the large trans-Neptunian object (174567) Varda that was observed on September 10, 2018. Varda belongs to the high-inclination dynamically excited population, and has a satellite, Ilmarë, which is half the size of Varda.Aims We determine the size and albedo of Varda and constrain its 3D shape and density.Methods Thirteen different sites in the USA monitored the event, five of which detected an occultation by the main body. A best-fitting ellipse to the occultation chords provides the instantaneous limb of the body, from which the geometric albedo is computed. The size and shape of Varda are evaluated, and its bulk density is constrained using Varda’s mass as is known from previous works.Results The best-fitting elliptical limb has semi-major (equatorial) axis of (383 ± 3) km and an apparent oblateness of 0.066 ± 0.047, corresponding to an …

We report on the stellar occultation by (523764) 2014 WC 510 observed on 2018 December 1 UT. This occultation campaign was part of the Research and Education Collaborative Occultation Network (RECON), a network of small telescopes spread over 2000 km in western USA and Canada. Light curves from six stations revealed three groups of two or more consecutive flux drops correlated in time between adjacent stations. A Bayesian model comparison reveals that a model with a double object occulting a double star is favored over alternative models considered. For the statistically favored model, we determined that the primary component of the object has a diameter d p= 181±16 km and the secondary d s= 138±32 km, assuming identical geometric albedo between the two components. The two components have a projected separation of 349±26 km. Adopting an absolute magnitude for the system of H V= 7 …

In table A1, we give astrometric observations of the trans-Neptunian (174567) Varda that were performed by our group using several telescopes between April 2013 and July 2019.

The observations for this occultation campaign were part of the Research and Education Collaborative Occultation Network (RECON) project (Buie+, 2016AJ.... 151... 73B) in collaboration with the Lucky Star project (see Berard+, 2017AJ.... 154.. 144B; Leiva+, 2017AJ.... 154.. 159L; Ortiz+, 2017Natur. 550.. 219O). At the time of the event, the cross-track uncertainty was 8000km (0.14"), the 1σ timing uncertainty was 5minutes, and the probability of success was estimated to be 9% based on the RECON prediction and participation by all teams. The network covered from-0.11 σ to 0.09 σ in the cross-track direction. In the down-track direction, we planned to cover {+/-} 2.5 σ (30 minutes).

A stellar occultation by the extreme large-perihelion trans-Neptunian object (541132) Leleākūhonua (also known by the provisional designation of 2015 TG 387) was predicted by the Lucky Star project and observed with the Research and Education Collaborative Occultation Network on 2018 October 20 UT. A single detection and a nearby nondetection provide constraints for the size and albedo. When a circular profile is assumed, the radius is

Interest in offshore wind development in California is growing. In response, the Bureau of Ocean Energy Management (BOEM) has proposed priority areas for leasing, known ascall areas.'To appropriately evaluate these call areas, an estimate of power production using prospective turbine technology in these areas is needed. This study provides an updated and comprehensive characterization of offshore wind power potential within the two Central California call areas (Diablo Canyon and Morro Bay) using hourly wind data from the WIND Toolkit. Potential power production is evaluated using12 and 15 MW turbines under different inter-turbine spacing and wind farm size scenarios. Our comparative analysis shows similar daily and seasonal patterns of wind power produced within the call areas, which peak in spring and during evening hours. The per-turbine power production is higher in the Morro Bay call area …