Bio-optical and physical measurements were collected in the Mississippi Sound (Northern Gulf of Mexico) during the spring of 2018 as part of the Integrated Coastal Bio-Optical Dynamics project. The goal was to examine the impact of atmospheric and tidal fronts on fine-scale physical and bio-optical property distributions in a shallow, dynamic, coastal environment. During a 25-day experiment, eight moorings were deployed in the vicinity of a frontal zone. For a one-week period in the middle of the mooring deployment, focused ship sampling was conducted with aircraft and unmanned aerial vehicle overflights, acquiring hyperspectral optical and thermal data. The personnel in the aircraft located visible color fronts indicating the convergence of two water masses and directed the ship to the front. Dye releases were performed on opposite sides of a front, and coincident aircraft and unmanned aerial vehicle overflights were collected to facilitate visualization of advection/mixing/dispersion processes. Radiometric calibration of the optical hyperspectral sensor was performed. Empirical Line Calibration was also performed to atmospherically correct the aircraft imagery using in situ remote sensing reflectance measurements as calibration sources. Bio-optical properties were subsequently derived from the atmospherically corrected aircraft and unmanned aerial vehicle imagery using the Naval Research Laboratory Automated Processing System.

A recent many-body quantum approach to thermal radiation (Smith GB, et al 2022 J. Phys. Commun. 6 , 065004 ) reveals that the energy capacitance of heated water is about twice its heat capacitance, due to energy stored as local hybrid pairs of photons coupled resonantly to local matter excitations, with pair density weighted by mass density. Energy exchange between photons and localised dipole excitations inside water at steady temperature T, occurs at sites where a hybridisation potential within the Hamiltonian couples local oscillation modes to ‘free’ photon modes. Photon modes in both directions are phase retarded at exit sides of a hybrid site. Optically sharp variations with frequency in the index of refraction n(f) and photon density of states follow. Exit spectral intensities at equilibrium temperature T carry quantum information on the energy density of matter excitations coupled to photons, while occupied hybrid sites are the source of all ‘free’ photons and internal spectral intensities. The matter excitations coupled locally to photons are distinct from those that define specific heat, but in water both arise from molecular oscillations. The energy capacitance C _EX (T) of hybrid pairs depends on mass density and is independent of the heat capacitance C _HT (T), which sets temperature T. C _EX (T) is sensitive to T and doubles as a capacitance of energy and of ‘quantum information’. Expressions for C _EX (T) are derived from first principles and applied to water. The density of occupied hybrids is amplified near surfaces by photons reflected off the surface, which create new hybrid pairs, but not extra heat. Energy capacitance C _EX (T)+C _HT (T) sets dT(t)/dt prior to a new equilibrium state emerging, after input heating rate dQ/dt is switched. Rising atmospheric intensities then raise T, dQ/dt, C _EX (T) and C _HT (T). The times available to cool overnight are fixed, so that a rising capacitance, adds to energy stored at an accelerating rate.

Photons excited into ground state modes at finite temperature display partitioning among photon phases, lifetimes and distances travelled since creation. These distributions set the distance from an interface a created photon has some chance of emission. Excited photons have phase velocity set by their mode’s propagation index n which sets mode density then internal energy contribution. All photons that strike an interface obliquely if emitted are refracted, and their exit intensities are irreversible except when weak internal attenuation occurs. Attenuation index k near zero degrees is small, so reversibility is approximate. As temperature rises refraction of exiting photons varies. Total emission remains reversible after transitioning through a nonequilibrium state with no other heat inputs. In equilibrium the densities of excitations that create and annihilate photons are in balance with photon densities, and emissivity dependent on n, k, temperature, and internal incident direction. Exit intensities from pure water and crystalline silica are modelled. They contain strong resonant intensities, and match data accurately. Intrinsic resonances formed within liquids and compounds are due to photon modes hybridising with localized excitations, including molecular oscillations and the anharmonic component of lattice distortions. They explain the many resonant spectral intensities seen in remote sensing. Each hybrid oscillator is a photonic virtual bound state whose energy fluctuates between levels separated by hf. Other features addressed are radiance when solid angle changes at exit, anomalous refraction, thermal recycling of internally reflected photons, fluxes within multilayers, and enhanced internal heat flux from phonon drag by photon density gradients under an external temperature gradient.

The Stefan-Boltzmann constant arose from photon densities inside a cavity, but inside matter photon mode densities are material specific. Photon speeds are governed by the mode they occupy, so mode densities can be expressed in terms of speed. Cavity intensities at temperature T_K combined [8π k^4/c^3h^3] T_K ^4 with (π^4/15). A material dependent number from summation of internal photon spectral energy densities replaces π^4/15. Spectral densities are presented for water, germanium and silver. Output intensity combines revised hemispherical emittance ϵ_Q,H based on these densities, with universal factor [8π k^4/c^3h^3] T_K ^4. Emitted radiance after interface internal reflectance of directionally invariant internal radiance elements defines ϵ_Q,H. Predicted internal densities are verifiable using measured external spectral intensities, provided refraction upon exit is accounted for in emissivity, which the Kirchhoff rule neglects. Virtual bound state photon resonances are predicted in dielectrics and observed.

An iterative algorithm is used to design a spectrally selective thin‐film stack to provide maximum solar‐to‐thermal conversion efficiency at the very high operating temperatures associated with high solar concentrations. The resulting stack is then fabricated by magnetron sputtering and characterized. It is composed of two Ta:SiO2 layers with differing Ta nanoparticle contents on a refractory metal substrate. A SiO2 antireflecting overlayer completes the stack. Optical and microstructural characterizations indicate that the stack achieves 97.6% solar absorptance up to 900 °C. Spectral selectivity and thermal stability improve on annealing in two ways, first, due to recrystallization of Pt or Ta back reflectors which lowers room temperature thermal emittance to 0.15 from 0.18, and to 0.14 from 0.21, respectively; and second, due to alloying of substrate atoms with the Ta nanoparticles of the cermet.

In this work we present the spatio-temporal characteristics of the surface expressions generated by various species of reef fish in visible and thermal wavebands with the intention of understanding the structures formed during locomotion, station-keeping, and feeding in a large scale aquarium environment. Data collected focused on diurnal events when the majority of the fish were active and overlapped with the feeding cycle of the marine animals. Expressions generated by a sea turtle (1 m) down to smaller fish (0.3 m) were observed and recorded with the resulting surface thermal footprints varying from one meter to several centimeters respectively. Surface thermal wakes and boils were recorded as fish swarmed near the surface, breached the water, and struck at food particles floating on the surface. This collection of surface thermal features serves as a template for expected outcomes in a more complex unconfined environment such as a harbor or blue water.

Spectrally-selective solar absorbing coatings based on the Ti1-xAlxN system were deposited using DC magnetron sputtering. Due to their refractory nature and very suitable optical properties, these were considered for high temperature solar thermal energy conversion. The composition of Ti1-xAlxN, (effectively, the Ti/Al ratio) was optimized to achieve a maximized solar absorptance. The optimum composition was then tested in a tandem absorber which included anti-reflective layers. A stainless steel substrate was used in order to simulate service in parabolic trough-based power plants that use stainless steel pipe to carry the heat-transfer fluid. High temperature annealing of the stack caused structural modifications but the solar absorptance of 92% was retained even after annealing at 900 °C.

Remote sensing of ocean properties from airborne platforms has expanded significantly in the last two decades. A number of new sensors and techniques have been developed to take advantage of the flexibility in timing, altitude, orientation, and frequency of measurements afforded by aircraft. Ocean properties measured from airborne platforms include ocean color, temperature, salinity, bathymetry, and a variety of wave characteristics among many others. Measurements are made with active and passive sensors collecting data from across the electromagnetic spectrum. These airborne measurements often support traditional ship-based sampling while providing expanded geospatial context.

Here we present our recent developments in temperature dependent ellipsometry, FTIR and emittance measurements of flat and structured vanadium dioxide (VO2) surfaces allowing significant control of switchable radiative cooling beyond that attainable via traditional VO2 surfaces. VO2 undergoes a metal-insulator transition at a critical temperature of ~ 68°C; previous work has investigated tuning of this critical temperature over a wide range of temperatures. Here we exploit the shift in optical properties to produce surfaces with various emittance temperature profiles that modulate the thermal radiative transfer to/from a surface. Designing surfaces with different temperature emittance profiles requires accurate optical/thermal characterisation of materials. VO2 is produced by sputtering of vanadium followed by post deposition annealing in a 0.1Torr to 0.3Torr Air atmosphere at 450°C to 550°C, in-situ optical monitoring allows for accurate termination of the annealing process once the desired optical response is achieved.

This study takes on the challenge of resolving upper ocean surface currents with a suite of airborne remote sensing methodologies, simultaneously imaging the ocean surface in visible, infrared, and microwave bands. A series of flights were conducted over an air-sea interaction supersite established 63 km offshore by a large multi-platform CASPER-East experiment. The supersite was equipped with a range of in situ instruments resolving air-sea interface and underwater properties, of which a bottom-mounted acoustic Doppler current profiler was used extensively in this paper for the purposes of airborne current retrieval validation and interpretation. A series of water-tracing dye releases took place in coordination with aircraft overpasses, enabling dye plume velocimetry over 100 m to 10 km spatial scales. Similar scales were resolved by a Multichannel Synthetic Aperture Radar, which resolved a swath of instantaneous surface velocities (wave and current) with 10 m resolution and 5 cm/s accuracy. Details of the skin temperature variability imprinted by the upper ocean turbulence were revealed in 1–14,000 m range of spatial scales by a mid-wave infrared camera. Combined, these methodologies provide a unique insight into the complex spatial structure of the upper ocean turbulence on a previously under-resolved range of spatial scales from meters to kilometers. However, much attention in this paper is dedicated to quantifying and understanding uncertainties and ambiguities associated with these remote sensing methodologies, especially regarding the smallest resolvable turbulent scales and reference depths of retrieved currents.

Understanding how turbulence impacts marine floc formation and breakup is key to predicting particulate carbon transport in the ocean. While floc formation and sinking rate has been studied in the laboratory and in-situ, the breakup response to turbulence has attracted less attention. To address this problem, the breakup response of bentonite clay particles flocculated in salt water was studied experimentally. Flocs were grown in a large aggregation tank under unmixed and mixed aggregation conditions and then subjected to turbulent pipe flow. Particle size was quantified using microscope imaging and in-situ measurements obtained from standard optical oceanographic instruments; a Sequoia Scientific LISST-100X and two WET Labs ac-9 spectrophotometers. The LISST instrument was found to capture the breakup response of flocs to turbulent energy, though the resulting particle size spectra appear to have underestimated the largest floc lengthscales in the flow while overestimating the abundance of primary particles. Floc breakup and the resulting shift towards smaller particles caused an increase in spectral slope of attenuation as measured by the ac-9 instruments. The Kolmogorov lengthscale was not found to have a limiting effect on floc size in these experiments. While the flocs were found to decrease in overall strength over the course of the two-month experimental time period, repeatable breakup responses to turbulence exposure were observed. Hydrodynamic conditions during floc formation were found to have a large influence on floc strength and breakup response. A non-constant strength exponent was observed for flocs formed with more energetic mixing. Increased turbulence from mixing during aggregation was found to increase floc fractal dimension and apparent density, resulting in a shift in the breakup relationships to higher turbulence dissipation rates. The results suggest that marine particle aggregation and vertical carbon transport concepts should include the turbulence energy responsible for aggregate formation and the resulting impact on floc strength, density, and the disruption potential.

This paper explores the use of infrared remote sensing methods to examine submesoscale eddies that recur downstream of a deep-water island (Santa Catalina, CA). Data were collected using a mid-wave infrared camera deployed on an aircraft flown at an altitude of 3.7 km, and research boats made nearly simultaneous measurements of temperature and current profiles. Structure within the thermal field is generally adequate as a tracer of surface fluid motions, though the imagery needs to be processed in a novel way to preserve the smallest-scale tracer patterns. In the case we focus on, the eddy is found to have a thermal signature of about 1 km in diameter and a cyclonic swirling flow. Vorticity is concentrated over a smaller area of about 0.5 km in diameter. The Rossby number is 27, indicating the importance of the centrifugal force in the dynamical balance of the eddy. By approximating the eddy as a Rankine vortex, an estimate of upward doming of the thermocline (about 14 m at the center) is obtained that agrees qualitatively with the in-water measurements. Analysis also shows an outward radial flow that creates areas of convergence (sinking flow) along the perimeter of the eddy. The imagery also reveals areas of localized vertical mixing within the eddy thermal perimeter, and an area of external azimuthal banding that likely arises from flow instability.

The global optimal solution (GOS) has proven to be very accurate for deriving water surface velocities from contemporaneous image pairs, but previous studies have used shore-based radars or satellite measurements with resolutions on the order of a kilometer or tens of meters to establish this. In contrast, the objective of this paper is to derive a GOS velocity field from infrared (IR) (3-5 mu m) images having a 1-m pixel size. Because IR images can frequently exhibit a low signalto-noise ratio, a newly developed GOS technique with a local similarity metric is used to retrieve velocities from such low-contrast data sets. To demonstrate the utility of this new method, we use airborne data collected in the tidal Potomac River over 11 days and spatially varying flood, ebb, and slack conditions. The resulting GOS-derived velocity estimates are compared against acoustic Doppler current profiler (ADCP) measurements taken simultaneously with the airborne collections. Velocity magnitudes and directions are found to have GOS versus ADCP correlations of 0.93 and 0.99, respectively. This high correlation suggests that the GOS technique may be applicable to a variety of lower contrast imagery that can now be collected by a low-altitude remotely controlled aircraft.

An unusual spatial pattern on the ocean surface was captured by thermal airborne swaths taken across a strong sea surface temperature front at the North Wall of the Gulf Stream. The thermal pattern on the cold side of the front resembles a staircase consisting of tens of steps, each up to ∼200 m wide and up to ∼0.3°C warm. The steps are well organized, clearly separated by sharp temperature gradients, mostly parallel and aligned with the primary front. The interpretation of the airborne imagery is aided by oceanographic measurements from two research vessels. Analysis of the in situ observations indicates that the front was unstable to symmetric instability, a type of overturning instability that can generate coherent structures with similar dimensions to the temperature steps seen in the airborne imagery. It is concluded that the images capture, for the first time, the surface temperature field of symmetric instability turbulence.

Cermet coatings based on nanoparticles of Au or Ag in a stable dielectric matrix provide a combination of spectral-selectivity and microstructural stability at elevated temperatures. The nanoparticles provide an absorption peak due to their localized surface plasmon resonance and the dielectric matrix provides red-shifting and intrinsic absorption from defects. The matrix and two separated cermet layers combined add mechanical support, greater thermal stability and extra absorptance. The coatings may be prepared by magnetron sputtering. They have solar absorptance ranging between 91% and 97% with low thermal emittance making them suitable for application in solar thermal conversion installations.

A generalized four-flux method capable of modeling and tuning the spectral reflectance of a diverse range of complex composite coatings is presented. An example application is exploring and maximizing the visible and near-infrared (IR) spectral reflectance available from the diverse structures arising from combinations of the many practical paint ingredients that are available or can be made when applied to different substrates. This requires consideration of scatterers that can differ in composition, particle size, size distribution, and fill factor, and are held in place by a variety of organic binders, which typically partially absorb in the near IR. This extended model is further enhanced by an explicit matrix algorithm that allows analysis of diverse multilayer stacks. This is applied to a multilayer and is designed to model useful changes that result from varying the pigment fill factor as a function of depth within a layer. What we believe is a novel feature is the way the scattering affects matrix absorptance. The model includes contributions to total absorptance from the scattering pigments and from the paint binder that can arise in different bands or simultaneously at the same wavelengths. Model accuracy is demonstrated by example results when compared to experimental data on dried single layer paint profiles using imaged cross sections. The model input covering the actual pigment and binder properties used are material, shape, size, and size distributions, mass added, and the measured optical constants from 400 nm to 2,500 nm of the undoped binder resin layer. One interesting result is the comparison of a two-layered stack, with bigger particles in the first layer and smaller ones in the second, to one with the opposite depth profile.

There has been continued recent interest in radiative sky cooling of coated flat surfaces that are able to passively attain sub-ambient temperatures. As the lowest incoming infrared radiation from a clear sky occurs at the zenith, a surface which sees mainly this region of the sky will receive much lower levels of sky radiation than one which views the whole sky, since the near-horizon contains significantly more incoming radiation. Two approaches to extra cooling are thus angular selectivity, which limits oblique outgoing as well as incoming radiation, and macroscopic reflectors which block oblique incoming sky radiation, while directing most outgoing emitted radiation towards the near zenith. This work focuses on the second of these techniques. We maximise cooling potential via coated 3D printed structures which can passively maintain a thermal reservoir below ambient temperature throughout the night and day. Novel design methods are used to fabricate and test structures which maximise outgoing thermal radiation from a surface, while minimising its illumination by incoming radiation from the sky and sun. Preliminary results gave 10°C below ambient both day and night during a Sydney spring. 3D printing allows the production of complex designed mirror cones with relatively low thermal conductivity. Post processing of the 3D printed structures allows the desired surface textures and optical properties to be created.

Power generation in solar energy systems, thermal control in buildings and mitigation of the Urban Heat Island problem, are all sensitive to directional response to incoming radiation. The radiation absorption and emission profile also plays a crucial role in each system's response and depends strongly on surface finish. This important sensitivity needs wider recognition in materials data sheets, system modeling, plus in materials and environmental engineering. The impact of surface roughness on thermal response of natural and man-made external environments is examined. Important examples will be given of the role of surface finish within each class. Total emittance links to the way surface finish influences directional emittance E(θ). Smooth surface thermal emittance on PV module covers, many solar absorbers, some roof paints, polished concrete, and glass windows can be up to 15% different from insulator results based on fully diffuse models of the same material. Widespread evidence indicates smooth metals and low-E solar absorber surfaces cool faster, and smooth insulators slower than previously thought. Matt paint is cooler than low sheen paint under the same solar heating impacts and normal concrete cooler than polished. Emittance for water is the prime environmental example of oblique impacts as it reflects strongly at oblique incidence, which leads to a significant drop in E(θ). Ripples or waves however raise water's average emittance. A surprise in this work was the high sensitivity of total E and its angular components to roughness in the depth range of 0.1–0.8 μm, which are well under ambient thermal IR wavelengths of 3–30 μm but common in metal finishing. Parallel energy flows such as evaporation and convective cooling vary if emittance varies. Thermal image analysis can provide insights into angular radiative effects.

Advanced solar energy collectors require the use of thermally stable and spectrally selective coatings in order to boost absorption of radiant energy. Here, it is shown that incorporation of plasmonically resonant Au and AuAl2 nanoparticles into multilayer coatings based on AlN provides strong and stable absorption across the solar spectrum at temperatures between RT and 500 °C. Optical properties at operating temperature are verified using in situ measurements. Solar absorptance of 92–97% is available in the as‐deposited films, which are comprised of layers of Al, Au:AlN, AlN, and SiO2. Annealing at the operating temperature of ∼500 °C causes the conversion of the elemental Au to the intermetallic compound AuAl2, but the good solar absorbing performance is retained. The additional Al that reacts with the Au nanoparticles to form the AuAl2 diffuses up from the reflective Al substrate used. Enhanced NIR solar absorptance post‐annealing is accompanied by a tolerable small rise in thermal emittance. Formation of AuAl2:AlN also prevents undesired Au nanoparticle agglomeration above 500 °C. This suggests that AuAl2:AlN nanoparticle composites are excellent candidates for solar thermal applications up to about 500 °C.