Ionosphere has importance for civilian and military Short Wave (SW) and satellite communications. Earthquakes, Solar Explosions and geomagnetic storms have effects on this layer. Electron density of ionosphere provides necessary information to investigate the ionospheric variability. In this study ionospheric variability over the Turkey are investigated using Cross Correlation Coefficient on IONOLAB-STEC data. The Slant Total Electron Content (STEC) data that are used are obtained from Turkish National Permanent GPS Network (TNPGN) stations.