Plotting contour on surface created with trisurf

I have scattered data in form of (x,y,z) that are points on a sphere. I have plotted the sphere using trisurf command and have used colormap on the basis of a vector Pindex.

code: tri=delaunay(x,y); trisurf(tri,x,y,z,Pindex); shading ineterp

I wish to draw contour lines on the sphere such that all points that have same value of Pindex are joined together through a single line. I tried with tricontour but was not successful.

Does anyone have an idea to proceed?