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% |
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% [JBz] = compute_JBz(SNAPSHOT) |
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% |
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% Here we compute the PV flux due to diabatic processes as |
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% JFz = - alpha * f * Qnet / MLD / Cw |
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% where: |
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% alpha = 2.5*E-4 1/K is the thermal expansion coefficient |
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% f = 2*OMEGA*sin(LAT) is the Coriolis parameter |
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% Qnet is the net surface heat flux (W/m^2), positive downward |
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% MLD is the mixed layer depth (m, positive) |
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% Cw = 4187 J/kg/K is the specific heat of seawater |
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% |
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% Files names are: |
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% INPUT: |
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% ./netcdf-files/<SNAPSHOT>/<netcdf_Qnet>.<netcdf_domain>.<netcdf_suff> |
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% ./netcdf-files/<SNAPSHOT>/<netcdf_MLD>.<netcdf_domain>.<netcdf_suff> |
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% OUTPUT: |
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% ./netcdf-files/<SNAPSHOT>/JBz.<netcdf_domain>.<netcdf_suff> |
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% |
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% with: netcdf_* as global variables |
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% |
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% 06/27/06 |
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% gmaze@mit.edu |
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|
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function varargout = compute_JBz(snapshot) |
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|
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global sla toshow |
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global netcdf_suff netcdf_domain |
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global netcdf_Qnet netcdf_MLD |
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pv_checkpath |
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|
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|
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% Path and extension to find netcdf-files: |
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pathname = strcat('netcdf-files',sla); |
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ext = netcdf_suff; |
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|
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% Load files: |
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ferfile = strcat(pathname,sla,snapshot,sla,netcdf_Qnet,'.',netcdf_domain,'.',ext); |
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ncQ = netcdf(ferfile,'nowrite'); |
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[Qlon Qlat Qdpt] = coordfromnc(ncQ); |
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|
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ferfile = strcat(pathname,sla,snapshot,sla,netcdf_MLD,'.',netcdf_domain,'.',ext); |
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ncMLD = netcdf(ferfile,'nowrite'); |
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[MLDlon MLDlat MLDdpt] = coordfromnc(ncMLD); |
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|
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|
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|
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%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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% surface PV flux |
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%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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|
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% Define axis: |
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nx = length(Qlon) ; |
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ny = length(Qlat) ; |
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nz = length(Qdpt) ; |
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|
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|
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% Planetary vorticity: |
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f = 2*(2*pi/86400)*sin(Qlat*pi/180); |
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[a f] = meshgrid(Qlon,f); clear a c |
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|
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|
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% Net surface heat flux: |
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Qnet = ncQ{4}(:,:,:); |
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|
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|
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% Mixed layer Depth: |
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MLD = ncMLD{4}(:,:,:); |
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|
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|
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% Coefficient: |
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alpha = 2.5*10^(-4); % Surface average value |
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Cw = 4187; |
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coef = - alpha / Cw; |
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|
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|
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% JBz: |
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JBz = zeros(nz,ny,nx).*NaN; |
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JBz(1,:,:) = coef*f.*Qnet./MLD; |
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|
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|
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|
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%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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% Record |
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%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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if toshow, disp('record'), end |
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|
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% General informations: |
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netfil = 'JBz'; |
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units = 'kg/m3/s2'; |
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ncid = 'JBz'; |
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longname = 'Vertical PV flux due to diabatic processes'; |
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uniquename = 'JBz'; |
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|
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% Open output file: |
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nc = netcdf(strcat(pathname,sla,snapshot,sla,netfil,'.',netcdf_domain,'.',ext),'clobber'); |
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|
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% Define axis: |
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nx = length(Qlon) ; |
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ny = length(Qlat) ; |
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nz = 1 ; |
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|
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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'} = 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'}(:) = Qlon; |
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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'}(:) = Qlat; |
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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'}(:) = Qdpt(1); |
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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}(:,:,:) = JBz; |
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|
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nc=close(nc); |
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close(ncQ); |
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close(ncMLD); |
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|
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|
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|
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% Output: |
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output = struct('JBz',JBz,'lat',Qlat,'lon',Qlon); |
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switch nargout |
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case 1 |
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varargout(1) = {output}; |
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end |
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