Read Ocean Current Data from NetCDF File in Matlab

Before create a script, make sure your Matlab has integrated with NetCDF toolbox, if don't have, you can search in google or any search engine to get toolbox, but in this post I use nctoolbox, for further information such as installation, guide and download nctoolbox open this site.

• Sea current data used here is NetCDF file, for example I use current data from Ocean Surface Current Analyses - Real time (OSCAR) NOAA which can be downloaded here.
• Download GSHHS shapefile here as a coastline.
• Open Matlab and use this script.

clc
clear all
close all

uc=ncgeodataset('arusindian.nc');

lat=uc.data('lat');
lon=uc.data('lon');
for i=find(lon>180):length(lon)
    lon(i)=lon(i)-360;
end

time=uc.time('time');%result 754324
tgl=datestr(time);

north =   max(lat);  % batas utara
south =   min(lat);  % batas selatan
west  =   min(lon);  % batas barat
east  =   max(lon);  % batas timur

s=gshhs('gshhs_l.b',[double(south) double(north)], [double(west) double(east)]);

    
arus_u=uc{'u'}(1,1,:,:);
arus_u=reshape(arus_u,size(arus_u,3),size(arus_u,4));

arus_v=uc{'v'}(1,1,:,:);
arus_v=reshape(arus_v,size(arus_v,3),size(arus_v,4));

dx=0.1;
[lon_r,lat_r]=meshgrid(west:dx:east+2,south:dx:north+2);
ucur=interp2(lon,lat,arus_u,lon_r,lat_r,'cubic'); 
vcur=interp2(lon,lat,arus_v,lon_r,lat_r,'cubic');

da=1.7;
[lon_a,lat_a]=meshgrid(west:da:east,south:da:north);
ucura=interp2(lon,lat,arus_u,lon_a,lat_a,'cubic');
vcura=interp2(lon,lat,arus_v,lon_a,lat_a,'cubic');

mag=sqrt(ucur.^2+vcur.^2);

quiver(lon_a,lat_a,ucura,vcura,'k','LineWidth',1.13);
hold on
pcolorjw(lon_r,lat_r,mag);
geoshow(s,'facecolor',[0 0 0]);
z=colorbar;
set(get(z,'ylabel'),'String','Speed (Knots)','fontweight','bold');

axis equal
axis([west east south north]);
caxis([0 1])
xlabel('Longitude','fontweight','bold');
ylabel('Latitude','fontweight','bold');
title(['Arus Muka Laut Pada ' tgl(1,:)],'fontweight','bold');
set(gcf,'renderer','zbuffer','paperpositionmode','auto');

here some sample I get,

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Read Wind Data from NetCDF File in Matlab

The steps similar with previous post about how to read SST file ......

Before create a script, make sure your Matlab has integrated with NetCDF toolbox, if don't have, you can search in google or any search engine to get toolbox, but in this post I use nctoolbox, for further information such as installation, guide and download nctoolbox open this site.

• Wind data used here are data from EMCWF which can be downloaded here.
• Download coastline data, you can use GSHHS or Coastline extractor from NOAA here,  both Matlab Script is a bit different, if you use GSHHS, the script to show coastline is similar with previous post, so in here I use coastline from Coastline extractor. 
• Open Matlab and use this script.

clc
clear all
close all

coast_line=load('korea-japan.dat');

north =   max(coast_line(:,2));  
south =   min(coast_line(:,2));  
west  =   min(coast_line(:,1));  
east  =   max(coast_line(:,1));  

nc=ncgeodataset('korea-japan-angin.nc');

lat=nc.data('latitude'); 
lon=nc.data('longitude');

tgl=nc.time('time'); 
date=datestr(tgl); 

v=nc{'v10'}(1,:,:);
v=reshape(v,size(v,2),size(v,3)); 
u=nc{'u10'}(1,:,:);
u=reshape(u,size(u,2),size(u,3));
        
dx_r=0.5;       
[lon_x,lat_x]=meshgrid(west:dx_r:east+2,south:dx_r:north+2);

u_wind_x=interp2(lon,lat,u,lon_x,lat_x,'spline');       
v_wind_x=interp2(lon,lat,v,lon_x,lat_x,'spline');

u_mag=sqrt(u_wind_x.^2+v_wind_x.^2);

pcolorjw(lon_x,lat_x,u_mag);shading('interp')
hold on
quiver(lon_x,lat_x,u_wind_x,v_wind_x,'k','Linewidth',1.2);
plot(coast_line(:,1),coast_line(:,2),'k','LineWidth',1.2)
axis equal
axis([min(coast_line(:,1)) max(coast_line(:,1)) min(coast_line(:,2)) max(coast_line(:,2))])
caxis([1 10])
     
h=colorbar;
set(get(h,'title'),'String','v (m/s)','FontWeight','Bold');
title(['Kecepatan Angin Pada ' date(1,:)],'FontWeight','Bold'); 
set(gcf,'PaperPositionMode','auto');    

Here some sample I have,

Refference
agusset.files.wordpress.com/2008/02/modul_membaca_netcdf.pdf‎

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Read Sea Surface Temperature (SST) Data from NetCDF File in Matlab

It's simple, just follow this step.....

Before create a script, make sure your Matlab has integrated with NetCDF toolbox, if don't have, you can search in google or any search engine to get toolbox, but in this post I use nctoolbox, for further information such as installation, guide and download nctoolbox open this site.

• SST file used here is NetCDF file, for example I use SST data from Earth System Research Laboratory (ESRL) NOAA which can be downloaded here.
• Download GSHHS Shapefile here as a coastline.
• Open Matlab and use this script.

clc
clear all
close all

utara=7;
selatan=-11;
barat=95;
timur=140;

negara=gshhs('gshhs_l.b',[selatan utara],[barat timur]);

dt=ncgeodataset('sst.mnmean.nc');

lon=dt.data('lon');
lat=dt.data('lat');
time=dt.data('time');
tgl=datestr(dt.time('time'));

for i=find(lon>180):length(lon)
    lon(i)=lon(i)-360;
end

sst=dt{'sst'}(length(time),:,:);
sst=reshape(sst,size(sst,2),size(sst,3));

dx=1;
[lon_r,lat_r]=meshgrid(barat:dx:timur+2,selatan:dx:utara+2);
sst_x=interp2(lon,lat,sst,lon_r,lat_r,'spline');
pcolorjw(lon_r,lat_r,sst_x); shading interp;
hold on
geoshow (negara,'FaceColor',[.1 .7 .1]);
level=[negara.Level];
geoshow(negara(level==2),'Facecolor',[0 0 1]);

axis equal
axis([barat timur selatan utara])
%caxis([25 30])
title(['Suhu Permukaan Laut Pada ' tgl(length(time),:)],'FontWeight','Bold');
xlabel('Longitude','FontWeight','Bold');
ylabel('Latitude','FontWeight','Bold');

h=colorbar;
set(get(h,'title'),'String','Suhu (^{\circ}C)','FontWeight','Bold');
set(gcf,'PaperPositionmode','auto');

here some sample I get,

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Create Bathymetry Map in Matlab from xyz Data

Matlab is a high-level computing language. There are many purpose using this program. In this post, I will describe how to make bathymetry map from xyz data in Matlab. Main idea of the process is only make x data, y data and z data to be a grid because of use surf command, so simple.

OK lets start .....

Before make a Matlab script, you must have xyz data, as an example I use data from  ETOPO 1 National Geophysical Data Center (NGDC) NOAA, you can download here. Select your area of interest and choose xyz data as an output format.

Steps in Matlab :

• Load your xyz data.
• x data is longitude, y data is latitude and z data is depth.
• Use unique command for x data and y data.

lon = unique(yourdata(:,1));
lat = unique(yourdata(:,2));

• Make a grid from lon and lat data

[LAT LON]=meshgrid(lat,lon);

• Make z data as a grid using this command.

for n=1:length(yourdata)
   ilon = find(lon==yourdata(n,1));
   ilat = find(lat==yourdata(n,2));
   depth(ilon,ilat) = yourdata(n,3);
end

• Use surf command.

surf(LON,LAT,depth);
shading interp;

• Run your matlab script.

This is example of resulting display

Bathymetry Map of England

Bathymetry Map of Indonesia

Bathymetry Map of Japan

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