Diurnal surface flux variability over western boundary currents

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution-NonCommercial‐NoDerivs License. The definitive version was published in Clayson, C. A., & Edson, J. B. Diurnal surface flux variability over western boundary currents. Geophysical Research Letters, 46(15), (2019): 9174-9182, doi:10.1029/2019GL082826.An analysis of a satellite ocean surface turbulent flux product demonstrated that, as expected, the western boundary current regions dominate the seasonal cycle amplitude. Surprisingly, our analysis of the global ocean diurnal flux variability also demonstrated a regional maximum in the winter over the western boundary current regions. We conducted comparisons with in situ data from several buoys located in these regions. The buoy data were in general agreement with the relative magnitude, timing, and importance of each of the bulk parameters driving the latent and sensible heat fluxes. Further analysis demonstrated that the strength and timing of the diurnal signal is related to the location of the buoy relative to the region of maximum heat flux and sea surface temperature gradient. In both regions, the timing of the higher winds coincides with the moistest surface layer, indicating that surface fluxes rather than entrainment mixing play a key role in this phenomenon.CAC gratefully acknowledges funding from the NASA MAP and NEWS programs (NNX13AN48G and NNX15AI47A). CLIMODE data were funded by the U.S. National Science Foundation (http://uop.whoi.edu/projects/CLIMODE/climodedata.html). KEO data are provided by the OCS Project Office of NOAA/PMEL (https://www.pmel.noaa.gov/ocs/data/disdel/). JKEO data are provided by RIGC/JAMSTEC and PMEL/NOAA (http://www.jamstec.go.jp/iorgc/ocorp/ktsfg/data/jkeo/). SeaFlux data are provided by the U.S. NOAA Climate Data Record Program (https://www.ncdc.noaa.gov/cdr)

On estimating the surface wind stress over the sea

Author Posting. © American Meteorological Society, 2018. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 48 (2018): 1533-1541, doi:10.1175/JPO-D-17-0267.1.Our study analyzes measurements primarily from two Floating Instrument Platform (FLIP) field programs and from the Air–Sea Interaction Tower (ASIT) site to examine the relationship between the wind and sea surface stress for contrasting conditions. The direct relationship of the surface momentum flux to U2 is found to be better posed than the relationship between and U, where U is the wind speed and is the friction velocity. Our datasets indicate that the stress magnitude often decreases significantly with height near the surface due to thin marine boundary layers and/or enhanced stress divergence close to the sea surface. Our study attempts to correct the surface stress estimated from traditional observational levels by using multiple observational levels near the surface and extrapolating to the surface. The effect of stability on the surface stress appears to be generally smaller than errors due to the stress divergence. Definite conclusions require more extensive measurements close to the sea surface.This work was supported by the U.S. Office of Naval Research through Award N00014-16-1-2600. We2019-01-1

A Multisensor Comparison of Ocean Wave Frequency Spectra from a Research Vessel during the Southern Ocean Gas Exchange Experiment

Obtaining accurate measurements of wave statistics from research vessels remains a challenge due to the platform motion. One principal correction is the removal of ship heave and Doppler effects from point measurements. Here, open-ocean wave measurements were collected using a laser altimeter, a Doppler radar microwave sensor, a radar-based system, and inertial measurement units. Multiple instruments were deployed to capture the low- and high-frequency sea surface displacements. Doppler and motion correction algorithms were applied to obtain a full 1D (0.035–1.3 ± 0.2 Hz) wave spectrum. The radar-based system combined with the laser altimeter provided the optimal low- and high-frequency combination, producing a frequency spectrum in the range from 0.035 to 1.2 Hz for cruising speeds ≤3 m s−1 with a spectral rolloff of f−4 Hz and noise floor of −20/−30 dB. While on station, the significant wave height estimates were comparable within 10%–15% among instrumentation. Discrepancies in the total energy and in the spectral shape between instruments arise when the ship is in motion. These differences can be quantified using the spectral behavior of the measurements, accounting for aliasing and Doppler corrections. The inertial sensors provided information on the amplitude of the ship’s modulation transfer function, which was estimated to be ~1.3 ± 0.2 while on station and increased while underway [2.1 at ship-over-ground (SOG) speed; 4.3 m s−1]. The correction scheme presented here is adequate for measurements collected at cruising speeds of 3 m s−1 or less. At speeds greater than 5 m s−1, the motion and Doppler corrections are not sufficient to correct the observed spectral degradation

Effects of rainfall on the atmosphere and the ocean during spurs-2

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Clayson, C. A., Edson, J. B., Paget, A., Graham, R., & Greenwood, B. Effects of rainfall on the atmosphere and the ocean during spurs-2. Oceanography, 32(2), (2019):86-97, doi: 10.5670/oceanog.2019.216.The salinity variability of the upper ocean is influenced by surface heat, momentum, and freshwater fluxes, which are in turn affected by atmospheric conditions. It is necessary to accurately measure these surface fluxes within their atmospheric environment to understand the linkages between rain events and the resulting upper-ocean salinity balance that occurs at cloud scales. We describe a comprehensive set of atmospheric and oceanic data collected during the second Salinity Processes in the Upper-ocean Regional Study (SPURS-2) experiment in the tropical eastern Pacific Ocean. These measurements included direct estimates of heat, moisture, and momentum fluxes using direct covariance flux systems on R/V Roger Revelle and a 3 m discus buoy. These are the first successful direct measurements of evaporation from a buoy over an extended period. The atmospheric moisture budget is estimated from a combination of data, including measured freshwater fluxes, upper air sounding data, and satellite data. This analysis reconfirms the important role of moisture convergence beneath the Intertropical Convergence Zone in this region. We perform an analysis of the near-surface vertical salinity structure and its relationship to these surface fluxes, highlighting the roles of stabilization by solar insolation and precipitation and the effects of rainfall on mixing of the upper ocean.This research was supported by NASA under grants NNX15AF70G and NNX15AG20G

Investigations of air-sea gas exchange in the CoOP Coastal Air-Sea Chemical Exchange project

Author Posting. © Oceanography Society, 2008. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 21, 4 (2008): 34-45.The exchange of CO2 and other gases across the ocean-air interface is an extremely important component in global climate dynamics, photosynthesis and respiration, and the absorption of anthropogenically produced CO2. The many different mechanisms and properties that control the air-sea flux of CO2 can have large spatial and temporal variability, particularly in the coastal environment. The need for making short-time-scale and small-spatial-scale estimates of gas transfer velocity, along with the physical and chemical parameters that affect it, provided a framework for the field experiments of the Coastal Ocean Processes Program (CoOP) Coastal Air-Sea Chemical Exchange (CASCEX) program. As such, the CASCEX project provided an opportunity to develop some of the first in situ techniques to estimate gas fluxes using micrometeorological and thermal imagery techniques. The results reported from the CASCEX experiments represent the first step toward reconciling the indirect but widely accepted estimates of gas exchange with these more direct, higher-resolution estimates over the coastal ocean. These results and the advances in sensor technology initiated during the CASCEX project have opened up even larger regions of the global ocean to investigation of gas exchange and its role in climate change.Funding for this work was provided by the National Science Foundation (NSF) CoOP program under grants OCE-9410534 and OCE-9711285

Note and Comment

Constitutional Privileges in the Philippine Islands; A Laudatory Publication as a Cause of Action; The Cy-Pres Doctrine; Duty of Vendee to See to Investment of Funds; the Power to Declare a forfeiture and Sell Property Used in Violation of a Statute; Dying Declarations; Juvenile Courts and Jury Trials for Neglected, Delinquent, Children

A surface mooring for air–sea interaction research in the Gulf Stream. Part I : mooring design and instrumentation

Author Posting. © American Meteorological Society, 2012. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Atmospheric and Oceanic Technology 29 (2012): 1363–1376, doi:10.1175/JTECH-D-12-00060.1.The design of a surface mooring for deployment in the Gulf Stream in the Mid-Atlantic Bight is described. The authors' goals were to observe the surface meteorology; upper-ocean variability; and air–sea exchanges of heat, freshwater, and momentum in and near the Gulf Stream during two successive 1-yr deployments. Of particular interest was quantifying these air–sea fluxes during wintertime events that carry cold, dry air from the land over the Gulf Stream. Historical current data and information about the surface waves were used to guide the design of the surface mooring. The surface buoy provided the platform for both bulk meteorological sensors and a direct covariance flux system. Redundancy in the meteorological sensors proved to be a largely successful strategy to obtain complete time series. Oceanographic instrumentation was limited in size by considerations of drag; and two current meters, three temperature–salinity recorders, and 15 temperature recorders were deployed. Deployment from a single-screw vessel in the Gulf Stream required a controlled-drift stern first over the anchor sites. The first deployment lasted the planned full year. The second deployment ended after 3 months when the mooring was cut by unknown means at a depth of about 3000 m. The mooring was at times in the core of the Gulf Stream, and a peak surface current of over 2.7 m s−1 was observed. The 15-month records of surface meteorology and air–sea fluxes captured the seasonal variability as well as several cold-air outbreaks; the peak observed heat loss was in excess of 1400 W m−2.This work was funded by the National Science Foundation Grant OCE04-24536 as part of the CLIVAR Mode Water Dynamics Experiment (CLIMODE). The Vetlesen Foundation is also acknowledged for the early support of SB.2013-03-0

Coastal mixing and optics experiment moored array data report

To investigate vertical mixing processes influencing the evolution of the stratification over continental shelves a moored array was deployed on the New England shelf from August 1996 to June 1997 as part of the Office of Naval Research's Coastal Mixing and Optics program. The array consisted of four mid-shelf sites instrumented to measure oceanic (currents, temperature, salinity, pressure, and surface gravity wave spectra) and meteorological (winds, surface heat flux, precipitation) variables. This report presents a description of the moored array, a summary of the data processing, and statistics and time-series plots summarizing the data. A report on the mooring recovery cruise and a summary of shipboard CTD surveys taken during the mooring deployment are also included.Funding was provided by the Office of Naval Research under Contract No. N00014-95-1-0339

Sea-to-air fluxes from measurements of the atmospheric gradient of dimethylsulfide and comparison with simultaneous relaxed eddy accumulation measurements

We measured vertical profiles of dimethylsulfide (DMS) in the atmospheric marine boundary layer from R/P FLIP during the 2000 FAIRS cruise. Applying Monin-Obukhov similarity theory to the DMS gradients and simultaneous micrometeorological data, we calculated sea-to-air DMS fluxes for 34 profiles. From the fluxes and measured seawater DMS concentrations, we calculated the waterside gas transfer velocity, kw. Gas transfer velocities from the gradient flux approach are within the range of previous commonly used parameterizations of kw as a function of wind speed but are a factor of 2 smaller than simultaneous determinations of transfer velocity using the relaxed eddy accumulation technique. This is the first field comparison of these different techniques for measuring DMS flux from the ocean; the accuracy of the techniques and possible reasons for the discrepancy are discussed