cdtcurldocumentation
cdtcurlcalculates the z component of curl for gridded vectors on an ellipsoidal Earth.
See also:cdtgradient,cdtdivergenceandekman.
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Contents
Syntax
Cz = cdtcurl(lat,lon,U,V)
Description
Cz = cdtcurl(lat,lon,U,V)usescdtdimto estimate the dimensions of each grid cell in thelat,longrid, then computes the curl of the gridded vectorsU,V.
Example
Load this sample of 10-meter windsuandv. Note that when we load the wind data, we're just taking the mean winds for this example.
文件名='ERA_Interim_2017.nc'; u = mean(ncread(filename,'u10'),3); v = mean(ncread(filename,“v10”),3); lat = double(ncread(filename,'latitude')); lon = double(ncread(filename,'longitude')); [Lat,Lon] = meshgrid(lat,lon);
The raw data are on a grid that goes from 0 to 360 longitude. I'd rather put the prime meridian in the middle of the map, so let'srecenterthe grids. This step isn't necessary, but it's a preference:
[Lat,Lon,u,v] = recenter(Lat,Lon,u,v);
Here are the winds on a global map:
figure earthimage holdonq = quiversc(Lon,Lat,u,v,'density',75); legend(q,'wind speed')
To illustrate the use of thecdtcurl函数,我们可以recreateFigure S11.03aof the Sixth Edition of Talley et al.'s book,Descriptive Physical Oceanography.
Start by using thewindstressfunction to convert the 10 meter wind speed vectors to wind stress in N/m^2:
[Taux,Tauy] = windstress(u,v);
Now usecdtcurlto get the global wind stress curl:
C = cdtcurl(Lat,Lon,Taux,Tauy);
Useislandto mask out the grid cells corresponding to land, and following Talley et al., multiply southern hemisphere curls by negative 1:
% Mask out land:land = island(Lat,Lon); C(land) = NaN; Taux(land) = NaN; Tauy(land) = NaN;% Multiply southern hemisphere curl by negative 1:C = C.*sign(Lat);
Now we're ready to recreate Talley et al.'s map relating wind stress to wind stress curl:
figure pcolor(Lon,Lat,C) shadingflatholdon% Overlay continents:边界('countries','facecolor',rgb('gray'),'edgecolor','none');% Overlay wind stress vectors:quiversc(Lon,Lat,Taux,Tauy,'k','density',100)% Jet is never a good idea, but we'll do it to mimic the published figure:colormap(jet(20))% Set the color axis limits and make a colorbar:caxis([-2 2]*1e-7) cb = colorbar('location','southoutside'); xlabel(cb,'wind stress curl x sign(lat) (\times10^{-7} N/m^3)')% Set map extents:axis([10 150 -60 30])% Format tick labels as degrees:xtickformat('degrees') ytickformat('degrees')
In case you're curious, here's the same figure with a more appropriate, divergent colormap fromcmocean(Thyng et al., 2016)
cmoceanbal
Author Info
This function is part of theClimate Data Toolbox for Matlab. The function and supporting documentation were written by Chad A. Greene of the University of Texas at Austin.