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gforget |
1.1 |
function [uvcurl]=calc_UV_curl(u,v,putCurlOnTpoints, doMask); |
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%[uvcurl]=calc_UV_curl(u,v,putCurlOnTpoints, [doMask]); |
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%object: compute curl of a vector field |
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%inputs: u,v is the vector field of interest |
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% putCurlOnTpoints states wherther to return the curl |
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% at curl points (0) or on tracer points (1) |
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% doMask: 0 to computer curl at all points (default) or 1 to |
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% mask so that curl is only computed at points that do not |
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% touch land (set to zero where touches land) |
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%output: [uvcurl] is the curl |
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gcmfaces_global; |
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if ~isfield(mygrid,'RAZfull'); |
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%get full RAZ (incl. 'extra line and column') |
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fprintf('\n calc_UV_curl requires loading (once) RAZfull \n'); |
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fprintf('into mygrid, so we now call grid_load_native_RAZ \n\n'); |
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grid_load_native_RAZ; |
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end; |
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if nargin < 4 |
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doMask=0; |
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end |
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if doMask |
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u(find(u==0))=NaN; v(find(v==0))=NaN; |
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end |
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%do the exchange: with sign changes for u and v, ... |
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nn=1; |
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[U,V]=exch_UV_N(u,v,nn); |
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%... without sign changes for DXC and DYC |
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[DXC,DYC]=exch_UV_N(mygrid.DXC,mygrid.DYC,nn); |
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U=U.*abs(DXC); V=V.*abs(DYC); |
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%compute the curl field |
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uvcurl=NaN*mygrid.RAZfull; |
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for iF=1:uvcurl.nFaces; |
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%define ucur, vcur as u,v on current face, with points that dont |
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%contribute to curl on that face removed. |
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ucur=U{iF}(2:end,:); |
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vcur=V{iF}(:,2:end); |
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tmpcurl=ucur(:,1:end-1)-ucur(:,2:end); |
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tmpcurl=tmpcurl-(vcur(1:end-1,:)-vcur(2:end,:)); |
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%deal with corners where only 3 point contribute to curl |
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if mod(iF,2)==1 %odd faces |
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vc=-vcur(1,1); %- S-W corner |
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tmpcurl(1,1) = (vcur(2,1)-ucur(1,2))+vc; |
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vc=vcur(end,1); %- S-E corner |
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tmpcurl(end,1) = (vc-ucur(end,2))-vcur(end-1,1); |
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vc=vcur(end,end); %- N-E corner |
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tmpcurl(end,end)=(vc-vcur(end-1,end))+ucur(end,end-1); |
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vc=-vcur(1,end); %- N-W corner |
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vc3=[vc vcur(2,end) ucur(1,end-1) vc vcur(2,end)]; |
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n=(iF+1)/2; |
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tmpcurl(1,end) = (vc3(n+2)+vc3(n+1))+vc3(n); |
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else %even faces |
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vc=-vcur(1,1); %- S-W corner |
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tmpcurl(1,1) = (vcur(2,1)-ucur(1,2))+vc; |
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vc=vcur(end,1); %- S-E corner |
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n=iF/2; |
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vc3=[-ucur(end,2) -vcur(end-1,1) vc -ucur(end,2) -vcur(end-1,1)]; |
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tmpcurl(end,1) = (vc3(n)+vc3(n+1))+vc3(n+2); |
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vc=vcur(end,end); %- N-E corner |
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tmpcurl(end,end)=(ucur(end,end-1)+vc)-vcur(end-1,end); |
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vc=-vcur(1,end); %- N-W corner |
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tmpcurl(1,end) = (vcur(2,end)+vc)+ucur(1,end-1); |
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end |
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tmpcurl=tmpcurl./mygrid.RAZfull{iF}; |
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%set points where NaN back to zero |
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tmpcurl(isnan(tmpcurl))=0; |
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%put to tracer points |
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if putCurlOnTpoints; |
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tmpcurl=1/4*(tmpcurl(1:end-1,2:end)+tmpcurl(1:end-1,1:end-1)+... |
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tmpcurl(2:end,2:end)+tmpcurl(2:end,1:end-1)); |
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end; |
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uvcurl{iF}=tmpcurl; |
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end; |
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