Either use writematrix, or use fprintf. See the documentation for examples.
If you use fprintf, be aware that it will go through an array column by column, but you read a file row by row.
Edit: here are examples for both.
SSS = rand(10,1);
Lat = rand(10,1)+1;
Lon = rand(10,1)+2;
writematrix([SSS Lat Lon],'test.txt');
type test.txt
fid = fopen('test2.txt','w');
fprintf(fid,'%.1f %.1f %.1f\n',[SSS,Lat,Lon].');
fclose(fid);
type test2.txt
