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Fig. 4.3.11 Cross-equatorial heat transport in petawatts (PW, 1015 W) as a function of time and latitude, from an Indian Ocean model driven with daily wind stresses (Loschnigg and Webster, 2000). earlier is (5i(x) 5y) pp. In the models, the Ekman transport augments the counterflow a few tens of metres below the surface downwind flow (Wacongne and Pacanowski, 1996 Garternicht and Schott, 1997). Some qualitative support for the idea that a Wacongne-Pacanowski cell may exist in the real ocean...

Interaction between eddies and mean flow

Spatial variability of the eddy Reynolds stress allows the study of the interaction between eddies and mean flow. Using only 1 year's worth of GEOSAT data, Tai and White (1990) showed some very interesting patterns of Reynolds stress convergence that suggested that the Kuroshio Extension was accelerated by a convergence of eddy momentum flux, while the mean flow was decelerated by a divergence to the north and south of the current. This finding is consistent with theoretical ideas of the growth...

The ocean general circulation

In the open ocean a few hundred km away from the equator, the large-scale oceanic flows are nearly in geostrophic and hydrostatic balance, leading to the integral form of the 'thermal wind' equation for the horizontal velocity at depth z where z0 is a reference level for the integration and v0 is the velocity at the reference level, p is the density of seawater, g is the earth's gravity acceleration, f is the Coriolis parameter defined as f 2ft sinwhere ft is the earth's rotation rate (7.292 x...

Interocean Exchange

Earth's climate, responding to the different thermodynamic properties of the land and ocean surfaces, is sensitive to the continental configuration and distribution of mountain ranges. This is clearly seen in the pattern of mean annual and seasonal range in such climate parameters as temperature and humidity and in the quasistationary patterns of atmospheric circulation, from small-scale sea breezes to planetary waves. Presumably because of the ocean-land configuration, each ocean basin is...

WCRP World Climate Research Programme

Prepared by the CLIVAR Scientific Steering Group, August 1995. World Climate Research Programme, WMO TD-No. 690, 157 pp. 7.4 WCRP (World Climate Research Programme), 1995b Comparison of TOGA tropical Pacific Ocean model simulations with the WOCE TOGA surface velocity programme drifter data set. Report Assembled by the Global Drifter Center and edited by WMO, June 1995. WCRP-No. 4 1995, 156 pp. 4.1 WCRP (World Climate Research Programme), 1998 CLIVAR Initial...

Applications how are SADCP and LADCP measurements changing our view of ocean currents and physics

The scientific role of ADCP observations is a function of their strengths and weaknesses relative to other types of observations. The main strengths are 1 measurement of absolute current profiles, in contrast with geostrophic profiles, which are always relative to an unknown reference 2 high horizontal and vertical resolution 3 measurement of both velocity components, also in contrast to geostrophic sections 4 low marginal cost, leading to a large data set. 1 accuracy limitations, particularly...

Estimation of current transport and variability

The temporal variability of the transport of surface currents can be readily determined from the difference in altimetric sea-surface-height anomalies (with temporal mean removed) across the domain of the current (Zlotnicki, 1991). Determination of the absolute velocity and transport of currents and eddies is problematic because the knowledge of the geoid at the mesoscale is not sufficiently accurate for oceanographic applications. Significant effort has been made to construct local geoid...

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Fig. 4.1.3 Schematic of SVP drifter. mounted on the upper portion. When the drogue was attached the surface float submerged often no submergence was observed when the drogue was detached. These drifters weighed about 24 kg when packed into biodegradable cardboard boxes that served also as deployment packages. When the drifters were deployed at sea, the transmitter emitted a 0.5-watt signal at 401.65 MHz, approximately every minute. This broadcast contained a...

Yz y

The essential feature of this Temporal-Residual-Mean (TRM) approach to the density equation is that it shows that the relevant three-dimensional density flux, namely the modified density flux, FM, can be decomposed into a non-divergent flux and a flux that is directed along the density surfaces, AVy. Moreover, this skew flux can be represented in the conservation equation as an extra advecting velocity (together with a different nondivergent flux). It can be shown that this same extra advecting...

Ocean Circulation And Climate Isbn 0126413517

Copyright 2001 Academic Press All rights of reproduction in any form reserved in-situ current measurements. At the time, direct current observations in the deep ocean were very limited, being restricted to about 20 locations in the Atlantic. Most were made by recording instruments suspended from anchored ships for durations between several hours and a few days. Bowden concluded there was great 'need for continuing the measurements at one station for a period of the order of a week to derive a...

Gf 9 8 7 6 5 4 3 2

Section 1 plates appear between pages 44 and 45 1.1.1 WOCE and the World Climate Research Programme 3 1.1.2 The scientific approach to the complex climate system 4 1.1.3 Ocean-atmosphere interaction and climate 5 1.1.4 Rapid changes related to the oceans 6 1.1.5 Cryosphere and the oceans 7 1.1.6 Anthropogenic climate change and the oceans 7 1.1.7 Future climate research and ocean observing systems 8 1.2 Ocean Processes and Climate Phenomena 11 Allyn Clarke, John Church and John Gould 1.2.1 A...

The WOCE Float Programme

There was, at the start of WOCE, great optimism that inverse analyses based on conserving transport of tracer water properties measured in the WOCE Hydrographic Programme could accurately estimate the absolute mean velocity of the general circulation. But for two reasons it was felt that direct observations of absolute subsurface flow should be included in the measurement programme. First, the precision that could be achieved by inverse analysis procedures was uncertain, but it was clear that...

Spacetime scales of ocean processes and models

The temporal and spatial scales of oceanic motions extend over many decades. A frequency-wave-number diagram is a convenient way to summarize scales of processes, even though it constitutes a linear view of a non-linear system and hence is necessarily limited in its interpretation. Figure 7.2.1 indicates the temporal and spatial scales of several relevant ocean processes. Also shown are the dispersion curves for gravity and planetary waves, in each case barotropic, and the first four baroclinic...

J S Godfrey G CJohnson MJ McPhaden G Reverdin and Susan EWijffels

4.3.1 Flow and water mass transformation patterns Most of the heat absorption into the global oceans, and much of the freshwater absorption, occurs in the tropics. Furthermore, Sea Surface Temperature (SST) is sufficiently high in the tropics that deep atmospheric convection can and does occur over it. Movements of deep convection patterns, which affect climate globally, depend sensitively on small changes in SST. Thus it is critically important for the improvement of global climate models that...

How the WHP defined standards for data and methods of measurement

The measurement techniques required for WOCE had been built up over a long period of time. But at the start of WOCE there were many parameters for which only a few groups in the world had the expertise to measure them to the required standard. Never before had a single coordinated hydro-graphic survey planned to draw on contributions from so many different institutions, investigators and countries. The question therefore arose of how to ensure that data were of a uniformly high standard,...

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Ekman Pumping

Fig. 5.3.1 (a) T S diagram from Iselin (1939) showing the T S relationship along the sea surface in winter in the western North Atlantic (open squares) and at depth (the solid line labelled Sargasso Sea) and along the sea surface in winter in the central North Atlantic (open circles) and at depth (the solid line labelled Eastern North Atlantic). Note that the surface and subsurface T S relationships are similar over only a small portion of the total temperature range shown. (b) T S diagram from...

Lowered ADCP systems

Although the LADCP and SADCP systems and algorithms are similar in many ways, there are some important differences relevant to LAD CP profile errors the LADCP depends much more critically on the inherent accuracy of the sonar. It is important to distinguish between the accuracy of the relative velocity profile as a function of vertical wavenumber, and the accuracy of the depth-averaged velocity - their error sources and characteristics are nearly independent. One must also distinguish...

Peter M Saunders

The deep and abyssal waters of the global ocean are produced at near-polar latitudes by the intense cooling of winter storms. The waters convect downwards and spread slowly equatorward, renewing the deepest and most distant layers of the global ocean on a time scale of several hundred years. In the south convection carries such water from the fringes of the Antarctic continent directly to great depths, particularly in the Weddell and Ross Seas. In the north, because of the topography of the...

DJWebb and N Suginohara

4.2.1 Processes in the ocean interior In this chapter we concentrate on the interior circulation of the ocean away from the equator and, for the most part, away from all boundaries. We will also generally concentrate on flows at scales larger than the Rossby radius. Our present knowledge about such flows comes from a mixture of hard in-situ observations and shrewd theoretical analysis. This combination works best in the top kilometre of the ocean where current velocities are relatively large....

Peter Niiler

Through many centuries mariners have observed ocean surface currents by noting how their vessels drift, and cartographers have prepared maps on the basis of these ship-drift reports. Instrumental observations of ocean currents on a global basis began about 115 years ago during the voyage of HMS Challenger. She left Portsmouth, England, on 21 December 1872, on an ocean expedition that was to navigate the globe in three and a half years. The measurements of the state of the ocean at 354 stations...

Nelson G Hogg

4.5.1 Deep circulation in the framework of WOCE During the design phase of the World Ocean Circulation Experiment (WOCE) it was recognized that various strategies were needed to 'divide and conquer' the massive problem of making a significant step forward in our understanding of the global circulation. One of these was a series of 'subject' meetings to contrast with the earlier 'sector' meetings at which different ocean basins had been the topic. One such meeting was held at Woods Hole in 1986...

Vertical coordinate systems

The choice of the vertical discretization is of particular importance for ocean circulation models. Currently, a variety of forms are used. Among these are models featuring alternative treatments of topography and the vertical coordinate. Examples include vertical coordinate systems based upon geopotential levels, isopycnal layers, and topography-following ('sigma') surfaces. While the first of these approaches is still the most prevalent, all three have by now been applied successfully to...

Extratropical Rossby waves

Westward propagation is a ubiquitous characteristic in a display of sea-level anomalies with a time-longitude section except within the vicinity of the equator (Fig. 3.3.7, see Plate 3.3.7, p. 172). Its interpretation in terms of Rossby waves has been documented in a large body of literature (Fu and Chelton, 2000). Identification of the source of these waves is not easy, but they are to a large extent forced by wind remotely. Because of the variability of the sea surface temperature associated...