•Horizontal LIDAR performance assessed via comparative study without experiment data.•Atmosphere model employed real visibility data and MODTRAN® solar spectral radiance.•Shiina LIDAR had better range resolution but inferior maximum detection range.•VAST LIDAR had superior detection and signal quality but very poor laser safety.•Hypothetical setup showed more balanced performance and met case study requirements. LIDAR performance is often evaluated after assembled prototypes are deployed for field tests. However, this approach is resource-intensive, which necessitates more cost-effective ways to detect flaws and improve LIDAR design. In this work, we present numerical assessment of horizontal scanning LIDAR performance via comparative study method. This assessment method could evaluate LIDAR performance without physically assembling the unit, hence save resources and time. We demonstrate this using a hypothetical atmospheric LIDAR. In our assessment, Python™ was used to develop simulation algorithm based on LIDAR equation, while Koschmieder visibility theory was used in atmosphere modeling. Daytime visibility and MODTRAN® solar spectral radiance data were also incorporated for analysis. We then evaluated LIDAR performance based on signal-to-noise and range-corrected signal profiles. Lastly, we conducted comparative study of this hypothetical LIDAR setup with Shiina (light emitting diode) LIDAR and VAST (ground-based) LIDAR for horizontal distance of 1 km. Numerical analysis showed that hypothetical LIDAR could operate up to 1 km at night. During daytime, detection was limited to 94 m and 220 m for 532 nm and 808 nm channels respectively. Comparative study demonstrated that the hypothetical LIDAR excelled in nighttime detection range with acceptable daytime performance. Overall, the hypothetical LIDAR has met case study requirements. We demonstrate the feasibility of this numerical assessment via comparative study method by identifying possible improvements in laser module without experimental data verification.