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  • Author or Editor: Clive E. Dorman x
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Clive E. Dorman and J. F. T. Saur

Abstract

Over the eight years of expendable bathythermograph observations from merchant ship transits between San Francisco and Honolulu have been analyzed to determine the nature of subsurface temperature anomalies. The irregularly distributed data were interpolated for 0, 90, 170 and 400 m by an objective analysis and then contoured. Statistical properties which had to be computed for the gridding procedure are described and presented.

The statistical properties and anomaly patterns in the upper layers are contrastingly different from those in the main thermocline and below. In the upper layers the significant correlation of anomalies is limited to time separation of less than 40 days, but extends to distance separations beyond 900 km. At the 170 m level in the main thermocline, anomalies are correlated to 100 days, but extend to only 190 km. The standard deviation increases from the surface to 170 m and then decreases to a minimum at 500 m. The peak of the standard deviation at a level shifts west as depth increases. Vertical correlations reveal that temperature anomalies at the surface are uncorrelated with those in the main thermocline. The main thermocline anomalies move along the route toward Honolulu at about 2.9 cm s−1, which is suggestive of baroclinic Rossby waves.

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Clive E. Dorman, C. A. Paulson, and W. H. Quinn

Abstract

Meteorological and oceanographic data for Ocean Station Vessel N (30N, 14OW) are analyzed over 20 years (1951–70) and 7 years (1964–70), respectively. A rainfall estimate is constructed for the 20-year period. The yearly average rainfall is 23 cm, far less than existing estimates. Daily and seasonal variations are presented. Heat budgets of the surface show that the two decades (1951–60, 1961–70) are distinctly different. Anomalies of the 20 years of all meteorological variables are calculated. The pressure anomaly appears to be loosely correlated with anomalous large-scale events in the equatorial Pacific. Time series cross sections are shown of the mixed layer depth, bottle temperature and salinity. The near-surface density appears to be largely controlled by temperature.

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Raymond W. Schmitt, Philip S. Bogden, and Clive E. Dorman

Abstract

Estimates of evaporation (E) over the North Atlantic Ocean by Bunker have been combined with estimates of precipitation (P) by Dorman and Bourke to produce new annual and seasonal maps of EP and surface density flux. Although uncertainties about precipitation algorithms and exchange coefficients still presist, it is felt that the high spatial resolution of these data set permits an estimate of EP that is a significant improvement over previous work. The maps of EP show considerably more detail than earlier maps, including a previously uncharted minimum with a northeast to southwest trend across the subtropical gyre. The two regions of maximal EP display a close connection with continental air flows off Africal and North America, suggesting that the relative narrowness of the North Atlantic contributes to its status as a net evaporation basin. The zonally integrated EP values are combined with river runoff estimates to obtain the meridional flux of freshwater, which can be compared with fluxes calculated from oceanographic sections.

Maps of the surface density flux are also presented for the annual and seasonal averages. Areas of net density gain by the ocean correspond to formation regions of subpolar mode water at high latitudes, 18°C water south of the Gulf Stream, and salinity maximum water at low latitudes in midgyre. The contributions of heat and salt to the density flux are separately computed. This reveals that the thermal density flux dominates at high and low latitudes whereas the haline density flux is most important in the subtropics, particularly on the eastern side of the basin. These data should facilitate the development of models of the thermohaline circulation, and aid the identification of regional differences in the dominant air–sea interaction processes.

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Darko Koračin, Clive E. Dorman, and Edward P. Dever

Abstract

Month-long simulations using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) with a horizontal resolution of 9 km have been used to investigate perturbations of topographically forced wind stress and wind stress curl during upwelling-favorable winds along the California and Baja California coasts during June 1999. The dominant spatial inhomogeneity of the wind stress and wind stress curl is near the coast. Wind and wind stress maxima are found in the lees of major capes near the coastline. Positive wind stress curl occurs in a narrow band near the coast, while the region farther offshore is characterized by a broad band of weak negative curl. Curvature of the coastline, such as along the Southern California Bight, forces the northerly flow toward the east and generates positive wind stress curl even if the magnitude of the stress is constant. The largest wind stress curl is simulated in the lees of Point Conception and the Santa Barbara Channel. The Baja California wind stress is upwelling favorable. Although the winds and wind stress exhibit great spatial variability in response to synoptic forcing, the wind stress curl has relatively small variation. The narrow band of positive wind stress curl along the coast adds about 5% to the coastal upwelling generated by adjustment to the coastal boundary condition. The larger area of positive wind stress curl in the lee of Point Conception may be of first-order importance to circulation in the Santa Barbara Channel and the Southern California Bight.

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