You can do that using a for loop
clear,clc
sorted_grid = rand(24,365);
index = rand(24,365);
combined = [zeros(size(sorted_grid)),zeros(size(index))];
idx = 0;
for col = 1:2:2*size(sorted_grid,2)-1
idx = idx+1;
combined(:,col) = index(:,idx);
combined(:,col+1) = sorted_grid(:,idx);
end
EDIT:
More efficient and elegant code
clear,clc
sorted_grid = rand(24,365);
index = rand(24,365);
combined = [zeros(size(sorted_grid)),zeros(size(index))];
combined(:,1:2:end-1) = index;
combined(:,2:2:end) = sorted_grid;
