We present a comprehensive model to study the atmospheric channel impairments within the low-and mid-latitude regions for the geostationary satellite-to-Earth-station (GEO-ES) links in the selective terahertz (THz) bands (140, 220, 345, and 410 GHz), in terms of dispersion, turbulence loss, as well as atmospheric attenuation in different seasons. Our analysis shows that dispersion effect in the channel above 300 GHz causes serious performance degradation in the low-latitude (LL) regions compared to mid-latitude regions, resulting in a need for a higher signal-to-noise-ratio (SNR) to achieve an expected bit-error-rate of, e.g., ^{10  −  3}. On the other hand, the GEO-ES link budget requirement becomes more stagnant due to turbulence loss in the LL regions compared to mid-latitude regions. In addition, seasonal variations investigation indicates that an improvement of 2- to 5-dB SNR can be obtained in the mid-latitude regions during winter. The influence of channel impairments on 16-QAM performance in an opto-electronic THz link with slant path geometry is analyzed as an example, and our results suggest that GEO-ES links operating in the 140- and 220-GHz bands are more foreseeably realistic in the low- and mid-latitude regions, whereas the 345-GHz band also shows a good potential for the future Earth-satellite THz links with high data capacity.