The GPS radio occultation (RO) technique is used to study sporadic E (<i>E<sub>S</sub></i>) layer plasma irregularities of the Earth’s ionosphere on a global scale using GPS signal-to-noise ratio (SNR) profiles from the COSMIC/FORMOSAT-3 satellite. The maximum deviation from the mean SNR can be attributed to the height of the <i>E<sub>S</sub></i> layer. <i>E<sub>S</sub></i> are generally accepted to be produced by ion convergence due to vertical wind shear in the presence of a horizontal component of the Earth magnetic field, while the wind shear is provided mainly by solar tides. Here we present analyses of quarterdiurnal (QDT) signatures in <i>E<sub>S</sub></i> occurrence rates. We find from a local comparison with mesosphere/lower thermosphere wind shear obtained with a meteor radar at Collm (51:3°N, 13:0°E), that the phases of the QDT in <i>E<sub>S</sub></i> agree well with those of negative wind shear for all seasons except for summer, when the QDT amplitudes are small. We also compare the global QDT <i>E<sub>S</sub></i> signal with numerical model results. The global distribution of <i>E<sub>S</sub></i> occurrence rates qualitatively agrees with the modeled zonal wind shears. The results indicate that zonal wind shear is indeed an important driving mechanism for the QDT seen in <i>E<sub>S</sub></i>.