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% |
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% [] = B_COMPUTE_RELATIVE_VORTICITY(SNAPSHOT) |
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% |
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% For a time snapshot, this program computes the |
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% 3D relative vorticity field from 3D |
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% horizontal speed fields U,V (x,y,z) as: |
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% OMEGA = ( -dVdz ; dUdz ; dVdx - dUdy ) |
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% = ( Ox ; Oy ; ZETA ) |
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% 3 output files are created. |
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% |
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% 06/07/2006 |
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% gmaze@mit.edu |
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% |
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|
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function [] = B_compute_relative_vorticity(snapshot) |
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|
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|
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%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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% Setup |
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%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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global sla netcdf_UVEL netcdf_VVEL netcdf_domain netcdf_suff |
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pv_checkpath |
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|
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|
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%% U,V files name: |
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filU = strcat(netcdf_UVEL,'.',netcdf_domain); |
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filV = strcat(netcdf_VVEL,'.',netcdf_domain); |
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|
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|
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%% Path and extension to find them: |
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pathname = strcat('netcdf-files',sla,snapshot,sla); |
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ext = strcat('.',netcdf_suff); |
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|
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|
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%% Load files: |
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ferfile = strcat(pathname,sla,filU,ext); |
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ncU = netcdf(ferfile,'nowrite'); |
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[Ulon Ulat Udpt] = coordfromnc(ncU); |
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|
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ferfile = strcat(pathname,sla,filV,ext); |
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ncV = netcdf(ferfile,'nowrite'); |
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[Vlon Vlat Vdpt] = coordfromnc(ncV); |
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|
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clear ext ferfile |
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|
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%% Optionnal flags |
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computeZETA = 1; % Compute ZETA or not ? |
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global toshow % Turn to 1 to follow the computing process |
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|
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|
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%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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% VERTICAL COMPONENT: ZETA % |
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%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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|
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% U field is on the zonal side of the c-grid and |
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% V field on the meridional one. |
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% So computing meridional gradient for U and |
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% zonal gradient for V makes the relative vorticity |
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% zeta defined on the corner of the c-grid. |
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|
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%%%%%%%%%%%%%% |
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%% Dimensions of ZETA field: |
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if toshow,disp('Dim'),end |
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ny = length(Ulat)-1; |
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nx = length(Vlon)-1; |
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nz = length(Udpt); % Note that Udpt=Vdpt |
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ZETA_lon = Ulon(1:nx); |
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ZETA_lat = Vlat(1:ny); |
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|
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%%%%%%%%%%%%%% |
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%% Pre-allocation: |
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if toshow,disp('Pre-allocate'),end |
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ZETA = zeros(nz,ny-1,nx-1).*NaN; |
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dx = zeros(ny-1,nx-1); |
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dy = zeros(ny-1,nx-1); |
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|
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%%%%%%%%%%%%%% |
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%% Compute relative vorticity for each z-level: |
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if computeZETA |
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for iz=1:nz |
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if toshow |
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disp(strcat('Computing \zeta at depth : ',num2str(Udpt(iz)),... |
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'm (',num2str(iz),'/',num2str(nz),')' )); |
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end |
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|
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% Get velocities: |
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U = ncU{4}(iz,:,:); |
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V = ncV{4}(iz,:,:); |
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|
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% And now compute the vertical component of relative vorticity: |
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% (TO DO: m_lldist accepts tables as input, so this part may be |
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% done without x,y loop ...) |
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for iy = 1 : ny |
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for ix = 1 : nx |
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if iz==1 % It's more efficient to make this test each time than |
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% recomputing distance each time. m_lldist is a slow routine. |
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% ZETA axis and grid distance: |
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dx(iy,ix) = m_lldist([Vlon(ix+1) Vlon(ix)],[1 1]*Vlat(iy)); |
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dy(iy,ix) = m_lldist([1 1]*Vlon(ix),[Ulat(iy+1) Ulat(iy)]); |
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end %if |
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% Horizontal gradients and ZETA: |
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dVdx = ( V(iy,ix+1)-V(iy,ix) ) / dx(iy,ix) ; |
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dUdy = ( U(iy+1,ix)-U(iy,ix) ) / dy(iy,ix) ; |
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ZETA(iz,iy,ix) = dVdx - dUdy; |
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end %for ix |
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end %for iy |
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|
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end %for iz |
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|
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%%%%%%%%%%%%%% |
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%% Netcdf record: |
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|
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% General informations: |
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netfil = strcat('ZETA','.',netcdf_domain,'.',netcdf_suff); |
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units = '1/s'; |
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ncid = 'ZETA'; |
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longname = 'Vertical Component of the Relative Vorticity'; |
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uniquename = 'vertical_relative_vorticity'; |
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|
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% Open output file: |
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nc = netcdf(strcat(pathname,sla,netfil),'clobber'); |
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|
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% Define axis: |
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nc('X') = nx; |
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nc('Y') = ny; |
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nc('Z') = nz; |
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|
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nc{'X'} = 'X'; |
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nc{'Y'} = 'Y'; |
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nc{'Z'} = 'Z'; |
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|
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nc{'X'} = ncfloat('X'); |
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nc{'X'}.uniquename = ncchar('X'); |
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nc{'X'}.long_name = ncchar('longitude'); |
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nc{'X'}.gridtype = nclong(0); |
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nc{'X'}.units = ncchar('degrees_east'); |
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nc{'X'}(:) = ZETA_lon; |
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|
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nc{'Y'} = ncfloat('Y'); |
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nc{'Y'}.uniquename = ncchar('Y'); |
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nc{'Y'}.long_name = ncchar('latitude'); |
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nc{'Y'}.gridtype = nclong(0); |
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nc{'Y'}.units = ncchar('degrees_north'); |
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nc{'Y'}(:) = ZETA_lat; |
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|
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nc{'Z'} = ncfloat('Z'); |
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nc{'Z'}.uniquename = ncchar('Z'); |
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nc{'Z'}.long_name = ncchar('depth'); |
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nc{'Z'}.gridtype = nclong(0); |
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nc{'Z'}.units = ncchar('m'); |
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nc{'Z'}(:) = Udpt; |
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|
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% And main field: |
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nc{ncid} = ncfloat('Z', 'Y', 'X'); |
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nc{ncid}.units = ncchar(units); |
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nc{ncid}.missing_value = ncfloat(NaN); |
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nc{ncid}.FillValue_ = ncfloat(NaN); |
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nc{ncid}.longname = ncchar(longname); |
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nc{ncid}.uniquename = ncchar(uniquename); |
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nc{ncid}(:,:,:) = ZETA; |
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|
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nc=close(nc); |
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|
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clear x y z U V dx dy nx ny nz DVdx dUdy |
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|
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end %if compute ZETA |
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|
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|
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%%%%%%%%%%%%%%%%%%%%%%%%% |
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% HORIZONTAL COMPONENTS % |
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%%%%%%%%%%%%%%%%%%%%%%%%% |
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if toshow, disp('') |
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disp('Now compute horizontal components of relative vorticity ...'); end |
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|
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% U and V are defined on the same Z grid. |
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|
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%%%%%%%%%%%%%% |
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%% Dimensions of OMEGA x and y fields: |
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if toshow,disp('Dim'),end |
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O_nx = [length(Vlon) length(Ulon)]; |
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O_ny = [length(Vlat) length(Ulat)]; |
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O_nz = length(Udpt) - 1; % Idem Vdpt |
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|
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%%%%%%%%%%%%%% |
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%% Pre-allocations: |
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if toshow,disp('Pre-allocate'),end |
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Ox = zeros(O_nz,O_ny(1),O_nx(1)).*NaN; |
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Oy = zeros(O_nz,O_ny(2),O_nx(2)).*NaN; |
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|
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%%%%%%%%%%%%%% |
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%% Horizontal components: |
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|
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%% Vertical grid differences: |
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dZ = diff(Udpt); |
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Odpt = Udpt(1:O_nz) + dZ/2; |
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|
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%% Zonal component of OMEGA: |
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if toshow,disp('Zonal direction ...'); end |
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[a dZ_3D c] = meshgrid(Vlat,dZ,Vlon); clear a c |
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V = ncV{4}(:,:,:); |
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Ox = - ( V(2:O_nz+1,:,:) - V(1:O_nz,:,:) ) ./ dZ_3D; |
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clear V dZ_3D % For memory use |
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|
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%% Meridional component of OMEGA: |
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if toshow,disp('Meridional direction ...'); end |
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[a dZ_3D c] = meshgrid(Ulat,dZ,Ulon); clear a c |
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U = ncU{4}(:,:,:); |
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Oy = ( U(2:O_nz+1,:,:) - U(1:O_nz,:,:) ) ./ dZ_3D; |
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clear U dZ_3D % For memory use |
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|
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clear dZ |
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|
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%%%%%%%%%%%%%% |
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%% Record Zonal component: |
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if toshow,disp('Records ...'); end |
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|
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% General informations: |
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netfil = strcat('OMEGAX','.',netcdf_domain,'.',netcdf_suff); |
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units = '1/s'; |
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ncid = 'OMEGAX'; |
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longname = 'Zonal Component of the Relative Vorticity'; |
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uniquename = 'zonal_relative_vorticity'; |
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|
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% Open output file: |
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nc = netcdf(strcat(pathname,sla,netfil),'clobber'); |
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|
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% Define axis: |
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nc('X') = O_nx(1); |
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nc('Y') = O_ny(1); |
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nc('Z') = O_nz; |
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|
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nc{'X'} = 'X'; |
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nc{'Y'} = 'Y'; |
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nc{'Z'} = 'Z'; |
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|
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nc{'X'} = ncfloat('X'); |
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nc{'X'}.uniquename = ncchar('X'); |
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nc{'X'}.long_name = ncchar('longitude'); |
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nc{'X'}.gridtype = nclong(0); |
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nc{'X'}.units = ncchar('degrees_east'); |
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nc{'X'}(:) = Vlon; |
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|
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nc{'Y'} = ncfloat('Y'); |
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nc{'Y'}.uniquename = ncchar('Y'); |
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nc{'Y'}.long_name = ncchar('latitude'); |
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nc{'Y'}.gridtype = nclong(0); |
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nc{'Y'}.units = ncchar('degrees_north'); |
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nc{'Y'}(:) = Vlat; |
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|
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nc{'Z'} = ncfloat('Z'); |
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nc{'Z'}.uniquename = ncchar('Z'); |
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nc{'Z'}.long_name = ncchar('depth'); |
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nc{'Z'}.gridtype = nclong(0); |
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nc{'Z'}.units = ncchar('m'); |
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nc{'Z'}(:) = Odpt; |
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|
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% And main field: |
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nc{ncid} = ncfloat('Z', 'Y', 'X'); |
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nc{ncid}.units = ncchar(units); |
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nc{ncid}.missing_value = ncfloat(NaN); |
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nc{ncid}.FillValue_ = ncfloat(NaN); |
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nc{ncid}.longname = ncchar(longname); |
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nc{ncid}.uniquename = ncchar(uniquename); |
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nc{ncid}(:,:,:) = Ox; |
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|
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nc=close(nc); |
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|
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%%%%%%%%%%%%%% |
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%% Record Meridional component: |
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% General informations: |
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netfil = strcat('OMEGAY','.',netcdf_domain,'.',netcdf_suff); |
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units = '1/s'; |
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ncid = 'OMEGAY'; |
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longname = 'Meridional Component of the Relative Vorticity'; |
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uniquename = 'meridional_relative_vorticity'; |
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|
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% Open output file: |
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nc = netcdf(strcat(pathname,sla,netfil),'clobber'); |
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|
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% Define axis: |
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nc('X') = O_nx(2); |
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nc('Y') = O_ny(2); |
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nc('Z') = O_nz; |
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|
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nc{'X'} = 'X'; |
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nc{'Y'} = 'Y'; |
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nc{'Z'} = 'Z'; |
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|
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nc{'X'} = ncfloat('X'); |
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nc{'X'}.uniquename = ncchar('X'); |
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nc{'X'}.long_name = ncchar('longitude'); |
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nc{'X'}.gridtype = nclong(0); |
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nc{'X'}.units = ncchar('degrees_east'); |
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nc{'X'}(:) = Ulon; |
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|
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nc{'Y'} = ncfloat('Y'); |
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nc{'Y'}.uniquename = ncchar('Y'); |
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nc{'Y'}.long_name = ncchar('latitude'); |
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nc{'Y'}.gridtype = nclong(0); |
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nc{'Y'}.units = ncchar('degrees_north'); |
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nc{'Y'}(:) = Ulat; |
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|
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nc{'Z'} = ncfloat('Z'); |
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nc{'Z'}.uniquename = ncchar('Z'); |
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nc{'Z'}.long_name = ncchar('depth'); |
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nc{'Z'}.gridtype = nclong(0); |
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nc{'Z'}.units = ncchar('m'); |
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nc{'Z'}(:) = Odpt; |
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|
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% And main field: |
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nc{ncid} = ncfloat('Z', 'Y', 'X'); |
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nc{ncid}.units = ncchar(units); |
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nc{ncid}.missing_value = ncfloat(NaN); |
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nc{ncid}.FillValue_ = ncfloat(NaN); |
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nc{ncid}.longname = ncchar(longname); |
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nc{ncid}.uniquename = ncchar(uniquename); |
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nc{ncid}(:,:,:) = Oy; |
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|
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nc=close(nc); |
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