[1] When upwelling favorable winds weaken or relax in coastal upwelling systems, prevailing equatorward currents often weaken and then reverse to form propagating poleward currents. Here the statistics of wind relaxations and poleward flow events along the south central California coast are derived using meteorological and oceanographic times series during [2000][2001][2002][2003][2004][2005][2006]. Over the 7-year record, 169 wind relaxations were observed (about 1 every 2 weeks) and 127 of these were followed by poleward flow events. Thermistor moorings and current profilers along the 15 m isobath at Alegria, Point Arguello, Point Purisima, and Point Sal recorded the poleward flows. The poleward flows propagate northward at 10-30 km dÀ1 and appear as sequential temperature increases at the moorings. Wind relaxations occur throughout the year but are most frequent in September and least frequent in April when upwelling winds are strong and persistent. Poleward flows follow wind relaxations frequently during May through November and rarely in December and January. Sea level differences between Santa Monica and Port San Luis, California, decreased as winds relaxed, consistent with forcing by alongshore pressure gradients. Temperature distributions at Point Arguello, Point Purisima, and Point Sal were skewed toward higher values because of the poleward flows. The alongshore distance traveled by the poleward flows increased with duration of the wind relaxations and magnitudes of alongshore temperature and sea level differences prior to the relaxations.

[1] Following relaxations of prevailing upwelling-favorable winds, warm waters from the Santa Barbara Channel propagate poleward around Point Conception and along the south central California coast. We examined characteristics of these relaxation flows, including frontal propagation speed and temperature changes during the warm water arrivals, by using multiyear time series of currents and temperatures from four moorings along the ∼15 m isobath, surface current observations from high-frequency radars, and satellite sea surface temperature images. Propagation speeds of the warm fronts relative to ambient waters ranged from 0.04 to 0.46 m s −1 . As the fronts arrived at the moorings, temperature increases ranged from 0.7°C to 4.2°C. In ensemble averages over many frontal arrivals, alongshore flow speeds increased by 0.1-0.2 m s −1 over the water column during arrivals. Cross-shore flows were onshore near the surface and offshore near the bottom with speeds of 0.02-0.05 m s −1 . This cross-shore flow structure persisted as temperature increased during arrivals and ceased when temperatures stopped increasing. Frontal propagation speeds were correlated with temperature increases at the moorings, consistent with forcing by baroclinic pressure gradients. Compared to other buoyant flows such as from the Chesapeake Bay where density contrasts with ambient waters are 2-3 kg m −3 , these relaxation flows are less buoyant with density contrasts of 0.1-0.9 kg m −3 . Consequently, the propagation of these flows is more affected by bottom friction and the speeds are closer to the "slope-controlled" or "bottom-advected" limit described in theoretical and laboratory work but not well studied in the ocean.Citation: Washburn, L., M. R. Fewings, C. Melton, and C. Gotschalk (2011), The propagating response of coastal circulation due to wind relaxations along the central California coast,

No abstract

An instrument is demonstrated that can be used for optical detection of honeybees in a cluttered environment. The instrument uses a continuous-wave diode laser with a center wavelength of 808 nm and an output power of 28 mW as the laser transmitter source. Light scattered from moving honeybee wings will produce an intensity-modulated signal at a characteristic wing-beat frequency (170-270 Hz) that can be used to detect the honeybees against a cluttered background. The optical detection of honeybees has application in the biological detection of land mines and explosives, as was recently demonstrated.

The Deepwater Horizon (DWH) oil blowout in the Gulf of Mexico (GoM) led to the largest offshore oil spill in U.S. history. The accident resulted in oil slicks that covered between 10,000 and upward of 40;000 km 2 of the Gulf between April and July 2010. Quantifying the actual spatial extent of oil over such synoptic scales on an operational basis and, in particular, estimating the oil volume (or slick thickness) of large oil slicks on the ocean surface has proven to be a challenge to researchers and responders alike. This challenge must be addressed to assess and understand impacts on marine and coastal resources and to prepare a response to future spills. We estimated surface oil volume and probability of occurrence of different oil thicknesses during the DWH blowout in the GoM by combining synoptic measurements (2330-km swath) from the satellite-borne NASA Moderate Resolution Imaging Spectroradiometer (MODIS) and nearconcurrent, much narrower swath (∼5 km) hyperspectral observations from the NASA Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). A histogram-matching approach was used to transfer AVIRIS-derived oil volume to MODIS pixel-scale dimensions, after masking clouds under both sun glint and nonglint conditions. Probability functions were used to apply the transformation to 19 MODIS images collected during the DWH event. This generated three types of MODIS oil maps: maps of surface oil volume, maps of relative oil thickness with four different classes (i.e., 0 μm, <0.08 μm, 0.08 to 8 μm, and >8 μm), and maps of probability distributions of different thicknesses. The results were compared with satellite-based synthetic aperture radar measurements and evaluated with concurrent aerial photographs. Although the methods may not be ideal and the results may contain large uncertainties, the current attempt suggests that coarseresolution optical remote sensing observations can provide estimates of relative oil thickness/volume for large oil slicks captured by satellites. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Reliability ranges provide the means to assess the clinical meaningfulness of results. The cohort differences are supported when the values exceed the ranges of the SEM; hence the amplitude results are meaningful. For dynamic shoulder elevation measured using video, the assessment of velocity was found to produce moderate to good reliability. The results suggest that with these measures subtle changes in both measures may be possible with further investigations.

This study explores Eulerian and Lagrangian circulation during weak winds at two inner-shelf locations off the Southern California coast where the shoreline, shelf, wind, and wave characteristics differ from those in previous studies. In agreement with recent observational studies, wave-driven Eulerian offshore flow just outside the surf zone, referred to as undertow, is a substantial component of the net cross-shore circulation during periods of weak winds. Drifter observations show onshore surface flow, likely due to light onshore winds, and a consistent decrease in onshore velocity of roughly 4 cm s 21 within a few hundred meters of the surf zone. Undertow is examined as a possible explanation for the observed Lagrangian decelerations. Model results suggest that, even when waves are small, undertow can decrease the velocity of shoreward-moving drifters by .2 cm s 21 , roughly half the observed deceleration. The coastal boundary condition also has the potential to contribute to the observed decelerations. Subtracting predicted Stokes drift velocities from the Lagrangian drifter observations improves the agreement between the drifter observations and coincident Eulerian ADCP observations.

Abstract. In this study, we present a novel approach for assessing nearshore seepage atmospheric emissions through modeling of air quality station data, specifically a Gaussian plume inversion model. A total of 3 decades of air quality station meteorology and total hydrocarbon concentration, THC, data were analyzed to study emissions from the Coal Oil Point marine seep field offshore California. THC in the seep field directions was significantly elevated and Gaussian with respect to wind direction, θ. An inversion model of the seep field, θ-resolved anomaly, THC′(θ)-derived atmospheric emissions is given. The model inversion is for the far field, which was satisfied by gridding the sonar seepage and treating each grid cell as a separate Gaussian plume. This assumption was validated by offshore in situ data that showed major seep area plumes were Gaussian. Plume total carbon, TC (TC = THC + carbon dioxide, CO2, + carbon monoxide), 18 % was CO2 and 82 % was THC; 85 % of THC was CH4. These compositions were similar to the seabed composition, demonstrating efficient vertical plume transport of dissolved seep gases. Air samples also measured atmospheric alkane plume composition. The inversion model used observed winds and derived the 3-decade-average (1990–2021) field-wide atmospheric emissions of 83 400 ± 12 000 m3 THC d−1 (27 Gg THC yr−1 based on 19.6 g mol−1 for THC). Based on a 50 : 50 air-to-seawater partitioning, this implies seabed emissions of 167 000 m3 THC d−1. Based on atmospheric plume composition, C1–C6 alkane emissions were 19, 1.3, 2.5, 2.2, 1.1, and 0.15 Gg yr−1, respectively. The spatially averaged CH4 emissions over the ∼ 6.3 km2 of 25 × 25 m2 bins with sonar values above noise were 5.7 µM m−2 s−1. The approach can be extended to derive emissions from other dispersed sources such as landfills, industrial sites, or terrestrial seepage if source locations are constrained spatially.