May 31, 2011 variations of the bifurcation latitude with season is simulated in a purely wind driven model and is found to be in agreement with recent observations. The wind stress is affected by the wind speed, the shape of the wind waves and the atmospheric. In no event shall the providers be liable for any damages, including without limitation, damages resulting from lost profits or revenue, or any special, incidental, or consequential damages, arising out of the use of these data. Evaluation of cmip3 and cmip5 wind stress climatology using. Bifurcation of the pacific north equatorial current in a wind. Monthly averaged wind stress curl climatology contour interval is 5 x 10 9 dyn. The climatology of surface pressure over the north pacific is. Chelton the scatterometer climatology of ocean winds scow was first released in november 2008 based on 8 years september 1999 august 2007 of quikscat scatterometer data. The central american wind jets extend at least 500 km into the pacific and produce distinctive curl dipoles as. This function determines the wind stress curl from wind data.
Climatological wind stress curl a and wind stress b distributions for aprilmay in the area off the west coast of the iberian. Scow seasonal cycles are compared with seasonal cycles estimated from ncepncar reanalysis wind fields. Climatological differences 198219771976 1971 for top wind stress and bottom surface. Effects of wind stress and wind stress curl variability on coastal. The relation of wind stress curl and meridional transport in. Oct 23, 2018 a close relationship between tropical instability wave tiw. The central american wind jets extend at least 500 km into the pacific and produce distinctive curl dipoles as wind strength. Gierach jet propulsion laboratory, california institute of technology, pasadena, california manuscript received 31 july 2012, in. Global wind stress magnitude fields oregon state university.
Influence of highresolution wind forcing on hydrodynamic. It is one of the components of the airsea interaction, with others being the atmospheric pressure on the water surface, as well as the exchange of heat and mass between the water and the atmosphere. Wind stress curl from wind data file exchange matlab central. Wind stress is extremely difficult to measure, but can be approximated by a bulk aerodynamic approach. The pat terns of wind stress curl are consistent with the existence of an equatorward sverdrup transport off. Cape frio, the coupling is intensified by up to 40%75%. Coupled effects of ocean current on wind stress in the bay. Impact of nearshore wind stress curl on coastal circulation.
Evaluation of cmip3 and cmip5 wind stress climatology using satellite measurements and atmospheric reanalysis products article pdf available in journal of climate 2616. Alongshore wind along the west coast of south america is an important component of typical eastern boundary upwelling systems driving offshore ekman transport near the surface and producing favorable wind stress curl near the shore hill et al. Comparison of wind speed and wind stress in the southern ocean. Variability of the wind stress curl over the north pacific. Comparisons with the ncepncar, ecmwf, uwmcoads, and hellerman and rosenstein datasets, journal of physical oceanography on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Ocean carbon uptake and storage influenced by wind bias in. The wind stress curl and hence ekman pumping anomalies were negative, which also is consistent with relatively weak entrainment. The cause of the biases in cmip wind stress climatology needs to be examined. Pdf evaluation of cmip3 and cmip5 wind stress climatology. This implies that given a stratification close to the observed, it.
The determinant influence of wind stress curl was evidenced, both in the representation of a mesoscale eddy structure and in the generation of a specific upwelling cell in the northwestern part of the gulf. May climatology from satellite observations for a vector wind stress, b magnitude of sst gradient, c wind stress curl, and d columnar water vapor, along with sst in contours. Risien and chelton 2008 present global and regional maps of wind stress, wind stress divergence, and curl annual, january and july means from eight years 19992007 of quikscat scatterometer data. Theories that explain the winddriven ocean circulation harald sverdrup 1947 showed that the circulation in the upper kilometer or so of the ocean is directly related to the curl of the wind stress if the coriolis force varies with latitude. The last relevant part here is that this kind of motion suppresses ocean mixing. The seasonal cycle is nearly independent of the wind climatology, but the annual average latitude depends on the wind stress curl. A close relationship between tropical instability wave tiw. North pacific intermediate water response to a modern climate. Annual mean annualmean climatologies of the wind stress and sst are shown in fig. The aim of this paper is to provide an overview of the resultant surface wind field accuracy and the gridded wind stress features. The dominant mechanisms involve basinscale wind stress curl forcing associated with, for example, a deepening of the aleutian low, rossby wave propagation and spinup of the subtropical gyre, which increases sst in the koe.
The scatterometer climatology of ocean winds scow c. Introduction the eastern tropical pacic displays a distinct meridional asymmetry, with cold sea surface temperatures. S, coaps has weaker correlation of wind stress with reanalysis data. The wind stress curl is of particular interest because it is the primary forcing mechanism for largescale ocean circulation. A global climatology of surface wind and wind stress fields. Hi,all of you if i have sea surface wind field u,v, how to obtain the curl of wind stress by ferret.
The wind stress curl is considered to be very important as it primarily drives largescale surfaceocean gyres or large circulating surface current systems and it has large seasonal variability. This dataset, referred to as the scatterometer climatology of. This dataset, referred to as the scatterometer climatology. P denotes the stress vector pa is the density of air which was considered to vi is the observed wind speed v is the observed wind. In the present work, many years of monthly mean surface wind curl is analysed to study the interannual variability. Gierach jet propulsion laboratory, california institute of technology, pasadena, california. Modeled sverdrup flow in the north atlantic from 11 different.
This drag force at the surface slows the wind speed and forms a boundary layer in the atmosphere. Broad regions of wsc result from largescale wind patterns, while mesoscale features of wsc accompany strong wind jets. A line of zero wind stress curl parallels the coast 200 to 300 km offshore, except off central baja california. Modeled sverdrup flow in the north atlantic from 11. Strong crossshelf and alongshore variability is apparent in the temporal mean and seasonal climatology of all four variables. Deep atmospheric response to the north pacific oceanic. During periods of high wind stress directional steadiness off. Wind stress curl variability over the north pacific from the.
The vertical component of the mathematical curl of the surface wind stress y. The curl of the wind stress was calculated from directly measured turbulent stress components. These features are similar to those described by milleret al. While this atlas, referred to here as the scatterometer climatology of ocean winds scow, consists of 12 variables, the focus here is on the wind stress and wind stress derivative curl and divergence fields. Thomas,4 timothy cowles,1 corinne james,1 luis sotomardones,5 and carlos cabrera2 received 3 august 2007.
Tiw, respectively has been identified from satellite observations. Pdf effects of wind stress and wind stress curl variability. The biases in cmip wind stress climatology are not sensitive to the decades over which the climatology was defined for cmip models and for the reference datasets see appendix. The wind stress curl is positive near the coast and negative in the region offshore.
This dataset, referred to as the scatterometer climatology of ocean winds scow, contains global seasonal cycles of the wind and wind stress fields estimated from the 122month record september 1999 october 2009 of wind measurements by the nasa quikscat scatterometer. We use these data to investigate the wind stress variability in the region around madagascar. The choice of wind stress climatology can be significant when studying largescale ocean dynamics since different wind stress products yield substantial differences in flow patterns, transport. The wsc exhibits seasonal variations along the coast and is in general much stronger in january than in july. The curl of the wind stress was calculated from directly. Global wind stress curl fields oregon state university. Bifurcation of the pacific north equatorial current in a. Evaluation of cmip3 and cmip5 wind stress climatology.
Two latitudinal regions are identified and separated at 44 46 n, where the coastal ocean experiences a change in the direction of the mean alongshore wind. Oceanography center flux climatology and referred to as noc hereafter. Ekman pumping and wind stress curl balance between coriolis and the vertical friction mixing of momentum, or stress, leads to ekman currents. Average a wind stress change in mn m 2, vectors indicate direction, b zonal surface velocity change in m s 1, and c vertical entrainment change averaged from 2. Variability of wind stress curl over the indian ocean during. A global climatology of surface wind and wind stress. Climatology of the 10m wind along the west coast of south. Read wind stress forcing of the ocean in the soc climatology. Variations of the bifurcation latitude with season is simulated in a purely winddriven model and is found to be in agreement with recent observations. Figure 8 shows time series of wind stress curl climatology averaged over the regions ac, bc, cc, and dc. Variables include scalar, zonal and meridional winds at 10meter high, and zonal and meridional components of wind stress. Aumont 2010, impact of nearshore wind stress curl on coastal circulation and primary productivity in the peru upwelling system, j.
Wind stress forcing of the ocean in the soc climatology. In physical oceanography and fluid dynamics, the wind stress is the shear stress exerted by the wind on the surface of large bodies of water such as oceans, seas, estuaries and lakes. Wind blowing over the sea surface exerts a stress on the ocean that imparts momentum. The wind stress curl is curl x y, where the components of the wind stress vector are and. The wind stress is affected by the wind speed, the shape of the wind waves and the atmospheric stratification. During ers1 live a regularly spaced wind vector, wind stress, wind divergence and wind stress curl with several key parameters are calculated from scatterometer wind observations.
The largescale, longterm averaged wind stress curl contains the principal information to calculate the winddriven mass transport. It is the force component parallel to the surface, per unit area, as applied by the wind on the water surface. The largescale, longterm averaged wind stress curl contains the principal information to calculate the winddriven mass. Satellitederived variability in chlorophyll, wind stress, sea surface height, and temperature in the northern california current system roberto m. Moreover, the scatterometer stable instrument records and era anomalies are statistically compared for quality assurance at the. The upper ocean response to winds wind stress and drag coefficients. Scow seasonal cycles are compared with seasonal cycles. Pdf oscat wind stress and wind stress curl products. This is the case in both hemispheres, because the sign of curl wind stress and f both differ, so w e climatology of ocean winds scow c. Using wind stress products with realistic nearshore patterns is therefore crucial for the modeling of coupled physical.
A global climatology of surface wind and wind stress fields from. The variability of regional weather is also related to largescale climate modes such. Wind stress curl and ocean conditions in the northeast. Influence of the meridional shifts of the kuroshio and the. For 18 models that submitted windstress fields to the world climate research programmes cmip3 archive 9, a monthly zonal windstress climatology was created using the last 100 years of the pre. The convergencesdivergences are directly related to the wind stress curl. Integrating this balance vertically in practice over the top few tens of meters gives us the ekman transport these components of ekman transport describe depth integrated flow in m 2 s1 i.
Wind stress and wind stress curl over the california current. Sensitivity to the meridional wind stress climatology andrew t. Wind stress curl from wind data file exchange matlab. Ted strub,1 emilio beier,2 ricardo letelier,1,3 andrew c. Henry stommel 1948 showed that the circulation in oceanic. Wind stress and curl anomalies along western north america. The maximum wsc peaks at ac in the spring, at bc in the summer, and at cc in the late summer. North pacific intermediate water response to a modern.
Waswind wave and anemometerbased sea surface wind provides a biascorrected marine surface wind dataset over the global oceans. P denotes the stress vector pa is the density of air which was considered to vi is the observed wind speed v is the observed wind velocity vector cd is an empirical drag coefficient. Objectively analyzed airsea fluxes for the global oceans. It is also shown that in the upper ocean, the poleward shift in bifurcation latitude with depth is realistic in our simple model. The offshore increase of the meridional wind stress component hereby contributes substantially to the formation of negative cyclonic wind stress curl wsc along the southwest african coast as shown in fig.
Effect of ocean surface currents on wind stress, heat flux. The accuracy of the computed curl was estimated to be adequate to map the spatial structure. The observed wind stress shows the prevailing southwesterly over the bay with a maximum of 0. The observed geostrophic current estimated from the soda features the narrow northeastwardflowing eicc in excess of 0. Evaluation of cmip3 and cmip5 wind stress climatology using satellite measurements and atmospheric reanalysis products tong lee,duane e. Conclusions climatological wind anomalies are investigated and being linked to other geophysical parameters for the cmems ocean state report. A numerical study of wind stress curl effects on eddies and. Satellitederived variability in chlorophyll, wind stress.
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