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Author: Brian Chinn
Publisher:
ISBN:
Category :
Languages : en
Pages : 120
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Author: Brian Chinn
Publisher:
ISBN:
Category :
Languages : en
Pages : 120
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Book Description
Author: Ellen Dunning Brown
Publisher:
ISBN:
Category : Eddies
Languages : en
Pages : 880
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Book Description
This thesis addresses several aspects of the problem of determining the effect of the low-frequency eddy variability on the mean circulation of the Western North Atlantic. A framework for this study is first established by scale analysis of the eddy and mean terms in the mean momentum, vorticity, and heat balances in three regions of the Western North Atlantic -- the northern recirculation, the southern recirculation, and the mid-ocean. The data from the last decade of field experiments suggest somewhat different conclusions from the earlier analysis of Harrison (1980). In the momentum balance we confirm that the eddy terms are negligible compared to the lowest order mean geostrophic balance. The eddy term may be an 0(1) term in the vorticity balance only in the northern recirculation region where the mean flow is anisotropic. In the mean heat balance, if the mean temperature advection is scaled using the thermal wind relation, then the eddy heat flux is negligible in the mid-ocean, but it may be important in the recirculation areas. For all the balances the eddy terms are comparable to or an order of magnitude larger than the mean advective terms. We conclude from the scale analysis that the eddy field is most likely to be important in the Gulf Stream recirculation region. These balances are subsequently examined in more detail using data from the Local Dynamics Experiment (LDE). Several inconsistencies are first shown in McWilliams' (1983) model for the mean dynamical balances in the LDE. The sampling uncertainties do not allow us to draw conclusions about the long-term dynamical balances. However, it is shown that if we assume that the linear vorticity balance holds between the surface and the thermocline for a finite record, then the vertical velocity induced by the eddy heat flux divergence is non-zero. The local effect of the mesoscale eddy field on the mean potential vorticity distribution of the Gulf Stream recirculation region is determined from the quasigeostrophic eddy potential vorticity flux. This flux is calculated by finite difference of current and temperature time series from the Local Dynamics Experiment. This long-term array of moorings is the only experimental data from which the complete eddy flux can be calculated. The total eddy flux is dominated by the term due to the time variation in the thickness of isopycnal layers. This thickness flux is an order of magnitude larger than the relative vorticity flux. The total flux is statistically significant and directed 217° T to the southwest with a magnitude of 1.57 x 10 -5 cm/2s. The direction of the eddy flux with respect to the mean large scale potential vorticity gradient from hydrographic data indicates that eddies in this region tend to reduce the mean potential vorticity gradient. The results are qualitatively consistent with numerical model results and with other data from the Gulf Stream recirculation region. We find that the strength of the eddy transfer in the enstrophy cascade is comparable to the source terms in the mean enstrophy balance. The Austauch coefficient for potential vorticity mixing is estimated to be 0(107cm2/sec). An order of magnitude estimate of the enstrophy dissipation due only to the internal wave field shows that other processes must be important in enstrophy dissipation. The measured eddy potential vorticity fluxes are compared to the linear stability model of Gill, Green, and Simmons (1974). An earlier study (Hogg, 1984) has shown agreement between the empirical orthogonal modes of the data and the predicted wavenumbers, growth rates, and phase speeds of the most unstable waves. However, we show substantial disagreement in a comparison of the higher moments the eddy heat and potential vorticity fluxes. Because the critical layer of the model is located near the surface, the model predicts that most of the eddy potential vorticity and eddy heat flux should occur within about 300 meters of the surface. The data show much greater deep eddy heat flux than predicted by the model. It is suggested that the unstable modes in the ocean have a longer vertical scale because of the reduction in the buoyancy frequency near the surface. The evidence for in situ instability is also examined in the decay region of the Gulf Stream from an array of current and temperature recorders. Although there is vertical phase propagation in the empirical orthogonal modes for some of the variables at some of the moorings, there is not much evidence for a strong ongoing process of wave generation.
Author: Matthew Suchley
Publisher:
ISBN:
Category :
Languages : en
Pages : 43
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Author: June Raven Marion
Publisher:
ISBN:
Category : Eddies
Languages : en
Pages : 148
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In this thesis, data collected during the Dynamics of the Madden Julian Oscillation (DYNAMO) field campaign, conducted in the Indian Ocean in Fall of 2011, is used to compute heat fluxes at the air-sea interface by evaluating eddy covariances and bulk aerodynamic formulae. Errors in daily average gridded fluxes computed with the COARE version 3.5 bulk aerodynamic formula are assessed with respect to five independent in situ time series from DYNAMO and the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE) in the Western Pacific (Nov. 1992 - Feb. 1993). Oregon State University (OSU), the NOAA Physical Science Division (PSD), and University of Connecticut (UConn) deployed three nearly collocated covariance flux measurement systems on the R/V Revelle during DYNAMO. Covariance and bulk fluxes are compared among these systems, and the experimental setup and calculation methods used for the OSU system are described. OAFlux and TropFlux are two gridded flux products, both of which use global atmospheric reanalyses and in situ observations to produce estimates of surface heat and momentum flux. An array of 106 buoys deployed in the Pacific, Atlantic, and Indian Oceans provide valuable in situ observations of surface meteorological variables including air and ocean temperatures, wind speed and relative humidity. The buoy data is assimilated into the reanalyses and incorporated into the bias correction strategy employed by TropFlux, and the optimal interpolation weights of OAFlux. Locations not constrained by observations have higher root mean square difference between these two products than those near buoys. In fact, OAFlux and TropFlux can sometimes disagree by 100% of the mean flux when buoy data sources are not nearby. Estimating net air-sea surface heat flux to an accuracy of 10 W/m2 requires resolution of diurnal solar warming of the ocean surface, known as the diurnal warm layer (Price, et al., 1986), and diffusive cooling of the viscous sub-layer known as the cool skin (Saunders, 1967). Warm layer and cool skin corrections to the bulk ocean temperature are modeled in the COARE bulk flux algorithm (Fairall et al., 1996). Rigorously calibrated and quality controlled DYNAMO data is used to assess the sensitivity of bulk flux calculations to warm layer and cool skin phenomena. Ignoring both corrections results in positive biases of 1.9 W/m2 and 8.7 W/m2 for sensible and latent heat respectively, mostly because of systematic overestimates of the SST due to the prominence of the cool skin. Two new techniques for including the effects of the warm layer and cool skin on daily fluxes are presented and tested using DYNAMO observations. Both techniques make use of a simple solar radiation model that distributes the daily average solar radiation in a half cosine over 12 hours of the day at hourly resolution. In the first technique the COARE algorithm computes warm layer and cool skin corrections hourly with the solar radiation model. This reduces the root mean square errors of sensible and latent heat fluxes to 0.7 and 2.9 W/m2. This improvement requires more than 10 bulk aerodynamic computations per day, a considerable computational expense when evaluating fluxes for decades of global gridded data. In the second technique, the daily average flux is evaluated beforehand in COARE using the solar radiation model with a range of daily average radiation and wind speed values. The results are sorted by solar radiation and wind speed in a lookup table that specifies an adjustment to the fluxes due to the warm layer and cool skin corrections. The adjustment corrects the daily fluxes computed without the warm layer and cool skin corrections. Using the lookup table corrections reduces the root mean square errors to 0.96 and 3.5 W/m2, nearly as well as the more computationally intensive diurnal solar model. The cool skin correction makes the biggest difference to the fluxes. Ignoring it can cause 10% overestimation of sensible and latent heat flux. Though they ignore the cool skin, both OAFlux and TropFlux estimate the R/V Revelle sensible and latent fluxes to within 0.1% of the mean flux. It is possible that fortuitous errors in the gridded products compensate the neglected effect of the cool skin. Diurnal warm layers intermittently warm the surface temperature during the convectively suppressed phase of the MJO. The warmest net (warm layer minus cool skin) daily mean difference between the bulk and interface temperature reaches 1° C, which is significant compared to the sea-air temperature difference on the order of 2° C. Observations of stronger diurnal warm layers in the convectively suppressed phase suggest that systematic intraseasonal modulation of the warm layer affects air-sea interaction in the MJO.
Author: Gerold Siedler
Publisher: Academic Press
ISBN: 9780126413519
Category : Business & Economics
Languages : en
Pages : 826
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Book Description
This book presents the views of leading scientists on the knowledge of the global ocean circulation following the completion of the observational phase of the World Ocean Circulation Experiment. WOCE's in situ physical and chemical measurements together with satellite altimetry have produced a data set which provides for development of ocean and coupled ocean-atmosphere circulation models used for understanding ocean and climate variability and projecting climate change. This book guides the reader through the analysis, interpretation, modelling and synthesis of this data.
Author: A. Bennett
Publisher:
ISBN:
Category :
Languages : en
Pages : 8
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Book Description
Estimates of meridonal heat flux in the North Pacific are reviewed. The 1976-1980 TRANSPAC XBT data is used to estimate transient and standing eddy heat fluxes above 400 dbar. The latter is marginally significant, due to an offshore meander in the Kuroshio path.
Author: P.M. Malanotte-Rizzoli
Publisher: Springer Science & Business Media
ISBN: 9401108706
Category : Science
Languages : en
Pages : 449
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Book Description
One of the most crucial but still very poorly understood topics of oceanographic science is the role of ocean processes in contributing to the dynamics of climate and global change. This book presents a series of high level lectures on the major categories of ocean/atmosphere processes. Three of these major issues are the focus of the lectures: (1) air--sea interaction processes; (2) water mass formation, dispersion and mixing; (3) general circulation, with specific emphasis on the thermohaline component. Global examples in the world ocean are provided and discussed in the lectures. In parallel, the Mediterranean Sea is a laboratory basin in providing analogues of the above global processes relevant to climate dynamics. They include the Mediterranean thermohaline circulation with its own `conveyor belt'; intermediate and deep water mass formation and transformations, dispersion and mixing. No other book in the field provides a review of fundamental lectures on these processes, coupled with global examples and their Mediterranean analogues.
Author:
Publisher: Academic Press
ISBN: 0123918537
Category : Science
Languages : en
Pages : 893
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Book Description
The book represents all the knowledge we currently have on ocean circulation. It presents an up-to-date summary of the state of the science relating to the role of the oceans in the physical climate system. The book is structured to guide the reader through the wide range of world ocean circulation experiment (WOCE) science in a consistent way. Cross-references between contributors have been added, and the book has a comprehensive index and unified reference list. The book is simple to read, at the undergraduate level. It was written by the best scientists in the world who have collaborated to carry out years of experiments to better understand ocean circulation. Presents in situ and remote observations with worldwide coverage Provides theoretical understanding of processes within the ocean and at its boundaries to other Earth System components Allows for simulating ocean and climate processes in the past, present and future using a hierarchy of physical-biogeochemical models
Author:
Publisher:
ISBN:
Category : Marine geodesy
Languages : en
Pages : 524
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Author: Detlef Stammer
Publisher: CRC Press
ISBN: 1498743463
Category : Science
Languages : en
Pages : 617
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Book Description
Satellite remote sensing, in particular by radar altimetry, is a crucial technique for observations of the ocean surface and of many aspects of land surfaces, and of paramount importance for climate and environmental studies. This book provides a state-of-the-art overview of the satellite altimetry techniques and related missions, and reviews the most-up-to date applications to ocean dynamics and sea level. It also discusses related space-based observations of the ocean surface and of the marine geoid, as well as applications of satellite altimetry to the cryosphere and land surface waters; operational oceanography and its applications to navigation, fishing and defense.
