Comparative analysis of calibration functions in the pure rotational Raman lidar technique

Abstract

Calibration functions (CFs) are required for the pure rotational Raman (PRR) technique to retrieve atmospheric temperature profiles from raw lidar data. The accuracy of temperature retrievals essentially depends on the selected CF, especially in the troposphere where the molecular collision effect dominates over the Doppler one. In this paper, we theoretically and experimentally compare nine different CFs (five of which are suggested for the first time) to determine the best function for the tropospheric temperature retrievals. All the CFs represent special cases of the general CF that takes into account the collisional broadening of individual atmospheric N2 and O2 PRR lines. The comparative analysis of calibration errors ΔTerr produced using these CFs in a simulation study showed that the best CF among them gives |ΔTerr| < 4 × 10− 5 K. To determine the best CF from a practical standpoint, we apply all the functions to nighttime measurement data obtained in Tomsk (56.48°N, 85.05°E, Western Siberia, Russia) with a PRR lidar designed in the Institute of Monitoring of Climatic and Ecological Systems (IMCES). The CF best-suited for the tropospheric temperature measurements with the IMCES PRR lidar is the same as determined by simulation.