I am skectching from excel importeed data but not getting smooth surfaces.

clc
data = xlsread('globalrd.xlsx','Sheet6') ; 
x = data(:,1) ; 
t = data(:,2) ; 
u = data(:,3) ; 
nx = length(unique(x)) ;
nt = length(unique(t)) ; 
X = reshape(x,nx,nt) ; 
T = reshape(t,nx,nt) ; 
U = reshape(u,nx,nt) ;
surf(T,X,U)
colorbar

[dpb]

That will be fully dependent upon the granularity/smoothness of the input data. To have a smoother surface will need more data points or to interpolate what you have.