Polarization profile differences between small and large zenith angle observations for PSRs J0636+5128 and J2033+1734, which contain enough number of observations. Panel (a), (b), (c) are the profile residuals for total intensity, linear and circular polarization, respectively. Panel (d) is the polarization profile from small zenith angle observations. The black, red, and blue represents total intensity, linear, and circular polarization, respectively. We normalize all the curves, such that the peak total intensity is 1.