Airborne lidar detection and characterization of internal waves in a shallow fjord

A dual-polarization lidar and photography are used to sense internal waves in West Sound, Orcas Island, Washington, from a small aircraft. The airborne lidar detected a thin plankton layer at the bottom of the upper layer of the water, and this signal provides the depth of the upper layer, amplitude of the internal waves, and the propagation speed. The lidar is most effective when the polarization filter on the receiver is orthogonal to the transmitted light, but this does not depend significantly on whether the transmitted light is linearly or circularly polarized. The depolarization is greater with circular polarization, and our results are consistent with a single parameter Mueller scattering matrix. Photographs of the surface manifestation of the internal waves clearly show the propagation direction and width of the phase fronts of the internal waves, even though the contrast is low (2%). Combined with the lidar profile, the total energy of the internal wave packet was estimated to be 9 MJ

Airborne Lidar Observations of a Spring Phytoplankton Bloom in the Western Arctic Ocean

One of the most notable effects of climate change is the decrease in sea ice in the Arctic Ocean. This is expected to affect the distribution of phytoplankton as the ice retreats earlier. We were interested in the vertical and horizontal distribution of phytoplankton in the Chukchi Sea in May. Measurements were made with an airborne profiling lidar that allowed us to cover large areas. The lidar profiles showed a uniform distribution of attenuation and scattering from the surface to the limit of lidar penetration at a depth of about 30 m. Both parameters were greater in open water than under the ice. Depolarization of the lidar decreased as attenuation and scattering increased. A cluster analysis of the 2019 data revealed four distinct clusters based on depolarization and lidar ratio. One cluster was associated with open water, one with pack ice, one with the waters along the land-fast ice, and one that appeared to be scattered throughout the region. The first three were likely the result of different assemblages of phytoplankton, while the last may have been an artifact of thin fog in the atmosphere.</div

Measurements from the RV Ronald H. Brown and related platforms as part of the Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC)

The Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC) took place from 7&nbsp;January to 11&nbsp;July&nbsp;2020 in the tropical North Atlantic between the eastern edge of Barbados and 51∘&thinsp;W, the longitude of the Northwest Tropical Atlantic Station (NTAS) mooring. Measurements were made to gather information on shallow atmospheric convection, the effects of aerosols and clouds on the ocean surface energy budget, and mesoscale oceanic processes. Multiple platforms were deployed during ATOMIC including the NOAA RV Ronald H. Brown (RHB) (7&nbsp;January to 13&nbsp;February) and WP-3D Orion (P-3) aircraft (17&nbsp;January to 10&nbsp;February), the University of Colorado's Robust Autonomous Aerial Vehicle-Endurant Nimble (RAAVEN) uncrewed aerial system (UAS) (24&nbsp;January to 15&nbsp;February), NOAA- and NASA-sponsored Saildrones (12&nbsp;January to 11&nbsp;July), and Surface Velocity Program Salinity (SVPS) surface ocean drifters (23&nbsp;January to 29&nbsp;April). The RV&nbsp;Ronald H. Brown conducted in situ and remote sensing measurements of oceanic and atmospheric properties with an emphasis on mesoscale oceanic&ndash;atmospheric coupling and aerosol&ndash;cloud interactions. In addition, the ship served as a launching pad for Wave Gliders, Surface Wave Instrument Floats with Tracking (SWIFTs), and radiosondes. Details of measurements made from the RV&nbsp;Ronald H. Brown, ship-deployed assets, and other platforms closely coordinated with the ship during ATOMIC are provided here. These platforms include Saildrone 1064 and the RAAVEN UAS as well as the Barbados Cloud Observatory (BCO) and Barbados Atmospheric Chemistry Observatory (BACO). Inter-platform comparisons are presented to assess consistency in the data sets. Data sets from the RV&nbsp;Ronald H. Brown and deployed assets have been quality controlled and are publicly available at NOAA's National Centers for Environmental Information (NCEI) data archive (https://www.ncei.noaa.gov/archive/accession/ATOMIC-2020, last access: 2 April 2021). Point-of-contact information and links to individual data sets with digital object identifiers (DOIs) are provided herein. &nbsp;</p

Optical Backscattering Measured by Airborne Lidar and Underwater Glider

The optical backscattering from particles in the ocean is an important quantity that has been measured by remote sensing techniques and in situ instruments. In this paper, we compare estimates of this quantity from airborne lidar with those from an in situ instrument on an underwater glider. Both of these technologies allow much denser sampling of backscatter profiles than traditional ship surveys. We found a moderate correlation (R = 0.28, p \u3c 10−5), with differences that are partially explained by spatial and temporal sampling mismatches, variability in particle composition, and lidar retrieval errors. The data suggest that there are two different regimes with different scattering properties. For backscattering coefficients below about 0.001 m−1, the lidar values were generally greater than the glider values. For larger values, the lidar was generally lower than the glider. Overall, the results are promising and suggest that airborne lidar and gliders provide comparable and complementary information on optical particulate backscattering

Hollow Aggregations of Moon Jellyfish (\u3ci\u3eAurelia\u3c/i\u3e spp.)

The relative importance of behavior and currents in forming and maintaining jellyfish aggregations is not completely understood; the objective of this work was to determine how the physical properties of the water column were related to the formation of hollow aggregations of moon jellyfish (Aurelia spp.). Hollow aggregations were observed near the surface by airborne lidar in shallow water (\u3c37 m) when the winds were light (\u3c4.3 m s-1). In this work, a hollow aggregation is defined as a region of few individuals surrounded by high densities in the two dimensions defined by depth and the direction of flight. Hydrographic profiles were available for most of the observations, and the bottom of the aggregation was correlated (R2 = 0.42, P = 8 × 10-4) with the depth of the shallow (\u3c13 m) surface mixed layer despite differences in position and time between the lidar observations and the hydrographic measurements. The size and shape of these aggregations suggests that they are not simply a result of advection by local currents, but of active behaviors. A likely mechanism is that the individuals are swimming in a vertical circle, and this behavior is predicted to enhance mixing at the top of the pycnocline

Surveying the Distribution and Abundance of Flying Fishes and Other Epipelagics in the Northern Gulf of Mexico Using Airborne Lidar

Flying fishes (family Exocoetidae) are important components of epipelagic ecosystems and are targeted by fishing fleets in the Caribbean Sea and elsewhere. However, owing to their anti-predator behavior and habitats, their ecology, abundance, and distributions are only partially known. From September 20 to October 6, 2011, we conducted a series of surveys over a large area (approximately 75,000 km2) of the northern Gulf of Mexico (87°W–90.5°W, 28°N–30°N). The surveys used an airborne lidar and vessel-based sampling, supported by near real time satellite observations of oceanic conditions. The aerial survey was conducted from a fixed wing aircraft that flew repeated surveys day and night, enabling data collection that was both broad-scale and synoptic. Vessel-based sampling included quantitative visual observations, trawl sampling, and qualitative dip-netting for species identifications. The combined surveys identified large aggregations of epipelagic organisms dominated by flying fishes. Large numbers of jellyfish (Aurelia sp.) and low numbers of numerous other species were also observed. The putative flying fish aggregations had an average length scale of 6.1 km and an average population estimated at 10,000 individuals. While always near the surface, flying fish aggregations were slightly deeper at night than during the day and found most often off the continental shelf in warm water with low chlorophyll concentrations. At least three species were present: Hirundichthys rondeletii (Valenciennes, 1847), Cheilopogon melanurus (Valenciennes, 1847), and Prognichthys occidentalisParin, 1999. This combination of aerial and surface surveys afforded repeated synoptic, ground-truthed data collection over a large area and indicates that this method could be useful for surveying such mobile epipelagic fishes

The tympanic membrane displacement analyser for monitoring intracranial pressure in children

Purpose: Raised intracranial pressure (ICP) is a potentially treatable cause of morbidity and mortality but tools for monitoring are invasive. We sought to investigate the utility of the tympanic membrane displacement (TMD) analyser for non-invasive measurement of ICP in children. Methods: We made TMD observations on normal and acutely comatose children presenting to Kilifi District Hospital (KDH) at the rural coast of Kenya and on children on follow-up for idiopathic intracranial hypertension at Evelina Children's Hospital (ECH), in London, UK. Results: We recruited 63 patients (median age 3.3 (inter-quartile range (IQR) 2.0-4.3) years) at KDH and 14 children (median age 10 (IQR 5-11) years) at ECH. We observed significantly higher (more negative) TMD measurements in KDH children presenting with coma compared to normal children seen at the hospital's outpatient department, in both semi-recumbent [mean -61.3 (95 % confidence interval (95 % CI) -93.5 to 29.1) nl versus mean -7.1 (95 % CI -54.0 to 68.3) nl, respectively; P = 0.03] and recumbent postures [mean -61.4 (95 % CI -93.4 to -29.3) nl, n = 59) versus mean -25.9 (95 % CI -71.4 to 123.2) nl, respectively; P = 0.03]. We also observed higher TMD measurements in ECH children with raised ICP measurements, as indicated by lumbar puncture manometry, compared to those with normal ICP, in both semi-recumbent [mean -259.3 (95 % CI -363.8 to -154.8) nl versus mean 26.7 (95 % CI -52.3 to 105.7) nl, respectively; P < 0.01] and recumbent postures [mean -137.5 (95 % CI -260.6 to -14.4) nl versus mean 96.6 (95 % CI 6.5 to 186.6) nl, respectively; P < 0.01]. Conclusion: The TMD analyser has a potential utility in monitoring ICP in a variety of clinical circumstances. © 2013 The Author(s)

Entrainment and Mixing of Transported Ozone Layers: Implications for Surface Air Quality in the Western U.S.

Recently, two air quality campaigns were conducted in the southwestern United States to study the impact of transported ozone, stratospheric intrusions, and fire emissions on ground-level ozone concentrations. The California Baseline Ozone Transport Study (CABOTS) took place in May – August 2016 covering the central California coast and San Joaquin Valley, and the Fires, Asian, and Stratospheric Transport Las Vegas Ozone Study (FAST-LVOS) was conducted in the greater Las Vegas, Nevada area in May – June 2017. During these studies, nearly 1000 hours of ozone and aerosol profile data were collected with the NOAA TOPAZ lidar. A Doppler wind lidar and a radar wind profiler provided continuous observations of atmospheric turbulence, horizontal winds, and mixed layer height. These measurements allowed us to directly observe the degree to which ozone transport layers aloft were entrained into the boundary layer and to quantify the resulting impact on surface ozone levels. Mixed layer heights in the San Joaquin Valley during CABOTS were generally below 1 km above ground level (AGL), while boundary layer heights in Las Vegas during FAST-LVOS routinely exceeded 3 km AGL and occasionally reached up to 4.5 km AGL. Consequently, boundary layer entrainment was more often observed during FAST-LVOS, while most elevated ozone layers passed untapped over the San Joaquin Valley during CABOTS