Direct covariance air-sea CO2 flux measurements over the open ocean are reported. These measureme... more Direct covariance air-sea CO2 flux measurements over the open ocean are reported. These measurements were performed during June 1998 in the North Atlantic within a significant CO2 sink. These direct estimates are in general agreement with the traditional geochemical isotope constraints. The covariance, or eddy correlation, technique directly measures the air-sea CO2 flux over hour timescales by correlating the fluctuations of CO2 with the turbulent vertical velocity fluctuations in the atmospheric surface layer. These measurements quantify the transfer of CO2 between the atmosphere and ocean over a range of wind speeds and improve the understanding of the environmental factors controlling the flux. The relatively large flux of CO2 in the study region, together with improved analytical techniques, facilitated the measurements. The half-hour mean wind speeds varied from 0.9 to 16.3 ms-1 over the month-long experiment. The mean pCO2 during the study period was -85.8+/-16.0muatm, and the mean covariance CO2 flux was estimated at 4.6 molm-2yr-1. The average observed wind speed was 7.7 ms-1. This is in close agreement with 3.9 molm-2yr-1, the approximate CO2 flux based on 14C parameterizations at this wind speed. At high winds, where the relationship between gas physical properties, surface processes, and air-sea gas exchange is still elusive, direct CO2 flux measurements are crucial. The measurements for winds in excess of 11 ms-1 show a general enhancement of gas transfer velocity over previous indirect measurements, and it is believed that this enhancement can be explained by the fact that the indirect methods cannot discriminate surface process variability such as atmospheric stability, upper ocean mixing, wave age, wave breaking, or surface films.
Surface flux, wind profiler, oceanic temperature and salinity, and atmospheric moisture, cloud, a... more Surface flux, wind profiler, oceanic temperature and salinity, and atmospheric moisture, cloud, and wind observations gathered from the R/V Altair during the North American Monsoon Experiment (NAME) are presented. The vessel was positioned at the mouth of the Gulf of California halfway between La Paz and Mazatlan (∼23.5°N, 108°W), from 7 July to 11 August 2004, with a break from 22 to 27 July. Experiment-mean findings include a net heat input from the atmosphere into the ocean of 70 W m−2. The dominant cooling was an experiment-mean latent heat flux of 108 W m−2, equivalent to an evaporation rate of 0.16 mm h−1. Total accumulated rainfall amounted to 42 mm. The oceanic mixed layer had a depth of approximately 20 m and both warmed and freshened during the experiment, despite a dominance of evaporation over local precipitation. The mean atmospheric boundary layer depth was approximately 410 m, deepening with time from an initial value of 350 m. The mean near-surface relative humidity ...
Because of the discovery of two errors in the calculations of long-wave radiative fluxes from the... more Because of the discovery of two errors in the calculations of long-wave radiative fluxes from the Eppley radiometers, a recalculation of the ice pack and surface energy budgets during the Arctic Leads Experiment (LEADEX) was necessary. The error princi- pally contributing to the observed differences was in the relationships that have been used for obtaining long-wave radiative fluxes from Eppley radiometers for the past 20 years. This paper focuses on the impacts on the LEADEX data. The main impacts of the correc- tions of these errors are decreases in the amplitudes of the diurnal variations of the long- wave fluxes and the skin temperature; an increase in the estimate of the sensible heat transfer coefficient (Ca) and the removal of its apparent diurnal cycle; and an interpretation of a more stable near-surface background atmosphere during the deployment to Lead 4. Average 10-m neutral values of the drag coefficient (Co) and Ca are now found to be 1.46 x 10 -3 and 1.40 x 10 -3, respectively.
Direct covariance air-sea CO2 flux measurements over the open ocean are reported. These measureme... more Direct covariance air-sea CO2 flux measurements over the open ocean are reported. These measurements were performed during June 1998 in the North Atlantic within a significant CO2 sink. These direct estimates are in general agreement with the traditional geochemical isotope constraints. The covariance, or eddy correlation, technique directly measures the air-sea CO2 flux over hour timescales by correlating the fluctuations of CO2 with the turbulent vertical velocity fluctuations in the atmospheric surface layer. These measurements quantify the transfer of CO2 between the atmosphere and ocean over a range of wind speeds and improve the understanding of the environmental factors controlling the flux. The relatively large flux of CO2 in the study region, together with improved analytical techniques, facilitated the measurements. The half-hour mean wind speeds varied from 0.9 to 16.3 ms-1 over the month-long experiment. The mean pCO2 during the study period was -85.8+/-16.0muatm, and the mean covariance CO2 flux was estimated at 4.6 molm-2yr-1. The average observed wind speed was 7.7 ms-1. This is in close agreement with 3.9 molm-2yr-1, the approximate CO2 flux based on 14C parameterizations at this wind speed. At high winds, where the relationship between gas physical properties, surface processes, and air-sea gas exchange is still elusive, direct CO2 flux measurements are crucial. The measurements for winds in excess of 11 ms-1 show a general enhancement of gas transfer velocity over previous indirect measurements, and it is believed that this enhancement can be explained by the fact that the indirect methods cannot discriminate surface process variability such as atmospheric stability, upper ocean mixing, wave age, wave breaking, or surface films.
Surface flux, wind profiler, oceanic temperature and salinity, and atmospheric moisture, cloud, a... more Surface flux, wind profiler, oceanic temperature and salinity, and atmospheric moisture, cloud, and wind observations gathered from the R/V Altair during the North American Monsoon Experiment (NAME) are presented. The vessel was positioned at the mouth of the Gulf of California halfway between La Paz and Mazatlan (∼23.5°N, 108°W), from 7 July to 11 August 2004, with a break from 22 to 27 July. Experiment-mean findings include a net heat input from the atmosphere into the ocean of 70 W m−2. The dominant cooling was an experiment-mean latent heat flux of 108 W m−2, equivalent to an evaporation rate of 0.16 mm h−1. Total accumulated rainfall amounted to 42 mm. The oceanic mixed layer had a depth of approximately 20 m and both warmed and freshened during the experiment, despite a dominance of evaporation over local precipitation. The mean atmospheric boundary layer depth was approximately 410 m, deepening with time from an initial value of 350 m. The mean near-surface relative humidity ...
Because of the discovery of two errors in the calculations of long-wave radiative fluxes from the... more Because of the discovery of two errors in the calculations of long-wave radiative fluxes from the Eppley radiometers, a recalculation of the ice pack and surface energy budgets during the Arctic Leads Experiment (LEADEX) was necessary. The error princi- pally contributing to the observed differences was in the relationships that have been used for obtaining long-wave radiative fluxes from Eppley radiometers for the past 20 years. This paper focuses on the impacts on the LEADEX data. The main impacts of the correc- tions of these errors are decreases in the amplitudes of the diurnal variations of the long- wave fluxes and the skin temperature; an increase in the estimate of the sensible heat transfer coefficient (Ca) and the removal of its apparent diurnal cycle; and an interpretation of a more stable near-surface background atmosphere during the deployment to Lead 4. Average 10-m neutral values of the drag coefficient (Co) and Ca are now found to be 1.46 x 10 -3 and 1.40 x 10 -3, respectively.
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Papers by Chris Fairall