Tmax below Mixed Layer

Tianyu Zhou, 11/10/2021, at UDel

Quality control and binning

Load data located within Nares Strait (pre-selected and stored in a '.mat' file) and perform quality control procedures.

% run the binning code that is the same as what is used before
preproce_binning

The depth of the first stability maximum and Tmax below it

depth_Nmax = ones(profi_num,1);
Tmax = ones(profi_num,1);
depth_Tmax = ones(profi_num,1);
depth_max = ones(profi_num,1);
S_Tmax = ones(profi_num,1);
for cast = 1:profi_num
    depth_max(cast) = max(output{cast,5}(:,2));
    % calculate pressure, absolute salinity and potential temperature
    lat = output{cast,4};
    lon = -output{cast,3};
    P =	gsw_p_from_z(-depth(cast,:),lat); 	     %pressure
    SA = gsw_SA_from_SP(S(cast,:),P,lat,lon);    %absolute salinity
    pT = gsw_pt_from_t(SA,T(cast,:),P,0);        %potential temperature
    
    % calculate conservative temperature and the stability frequency
    CT = gsw_CT_from_t(SA,T(cast,:),P);          %conservative temperature
    [N2, ~] = gsw_Nsquared(SA,CT,P,lat);
    
    % the first stability maximum
    diff_N2 = diff(N2);
    index = find(diff_N2 >= 0);
    n = 1;
    while diff_N2(index(n)+1) >= 0
        n = n+1;
    end
    depth_Nmax(cast) = depth(1,index(n)+1);
    pT(1:index(n)+1) = -999;
    pT(1:20) = -999;   % rule out the upper 20 m
    pT(end) = [];
    [Tmax(cast),index_Tmax] = max(pT);
    depth_Tmax(cast) = depth(1,index_Tmax);
    S_Tmax(cast) = S(cast,index_Tmax);    
end

Save results related to Tmax into a data file

year = cell2mat(output(:,1));
lon = -cell2mat(output(:,3));
lat = cell2mat(output(:,4));
outfile = [lat,lon,year,Tmax,depth_Tmax,S_Tmax];
save('WHW_10.dat','outfile','-ascii')

Plotting figures based on the results

% Temporal variation of Tmax, D(Tmax) and S(Tmax)

f = figure;

set(f,'units','centimeters','position',[1,1,13*1.5,9*1.5],'color','w')

FontSize = 15;

subplot(3,1,1)

plot(year,Tmax,'.','MarkerSize',12)

xlim([2015.5 2021.5])

ylim([-1 4.5])

ylabel('Tmax','FontWeight','bold')

set(gca,'FontSize',FontSize,'tickdir','out')

subplot(3,1,2)

plot(year,depth_Tmax,'.','MarkerSize',12)

hold on

depth_max = floor(depth_max);

plot(year(depth_Tmax==depth_max),depth_Tmax(depth_Tmax==depth_max),'.','MarkerSize',12,'Color','r')

xlim([2015.5 2021.5])

ylabel('D(Tmax)','FontWeight','bold')

set(gca,'FontSize',FontSize,'tickdir','out')

subplot(3,1,3)

plot(year,S_Tmax,'.','MarkerSize',12)

xlim([2015.5 2021.5])

ylim([28 36])

ylabel('S(Tmax)','FontWeight','bold')

xlabel('Years','FontWeight','bold')

set(gca,'FontSize',FontSize,'tickdir','out')

% T-S space

f = figure;

set(f,'units','centimeters','position',[1,1,15.5*1.5,10*1.5],'color','w')

FontSize = 20;

color = jet;

c_max = 800;

c_min = 200;

range = linspace(c_min,c_max,256);

for n = 1:profi_num

[~,pos] = min(abs(depth_Tmax(n)-range));

plot(S_Tmax(n),Tmax(n),'.','color',color(pos,:),'MarkerSize',17)

hold on

end

colormap("jet")

colorbar

caxis([c_min c_max])

cbarrow

xlabel('S(Tmax)','FontWeight','bold')

ylabel('Tmax (^{o}C)','FontWeight','bold')

title('D(Tmax) and Water Properties','FontWeight','bold')

set(gca,'FontSize',FontSize,'tickdir','out')

% Spatial distribution

lat_start = 77.5;

lat_end = 83.3;

lon_start = -85;

lon_end = -47;

f = figure;

set(f,'units','centimeters','position',[1,1,12*1.5,9*1.5],'color','w')

m_proj('mercator','lon',[lon_start lon_end],'lat',[lat_start lat_end]);

hold on

m_grid('box','on','linest','none','fontname','times','linewidth',0.1,'tickdir','out','backcolor',[1 1 1],'Fontsize',20);

m_gshhs_h('patch',[0.6 0.6 0.6]);

color = jet;

c_max = 1;

c_min = -0.5;

range = linspace(c_min,c_max,256);

for n = 1:profi_num

[~,pos] = min(abs(Tmax(n)-range));

m_plot(lon(n),lat(n),'.','color',color(pos,:),'markersize',20)

end

% Colorbar settings

colormap(color)

colorbar

caxis([c_min c_max])

cbarrow('up')

title('Spatial Distribution of Tmax')

set(gca,'fontsize',16,'color','w');