Temporal stability of calibration functions in the traditional pure rotational Raman lidar technique

Abstract

Pure rotational Raman (PRR) lidars should be calibrated to measure atmospheric temperature. In the frame of the traditional PRR technique, the lidar calibration represents the determination of calibration function (CF) coefficients using a reference temperature profile from an atmosphere model or radiosonde data. When a measurement campaign lasts several days, the accuracy of temperature retrieval from PRR lidar signals depends on the temporal stability of the selected CF. In this paper, we present a simple way to intercompare different CFs and determine the most stable function in time among them. We study to what extent the CF coefficients determined on one of the measurement campaign days may be used for temperature retrieval on the other days. We also examine the situation when reference radiosonde data are absent on one of the measurement days and, therefore, the CF coefficients need to be determined from reference data over the remaining days. The 1-week and 3-day temporal stabilities of five CFs are studied on the example of nighttime temperature profiles retrieved from PRR lidar measurements of 1, 6, 7, and 8 April 2015. The stability of these CFs is studied for the first time. The measurements were performed in Tomsk (56.48°N, 85.05°E, Western Siberia, Russia) using a PRR lidar of the Institute of Monitoring of Climatic and Ecological Systems (IMCES). The CF retrieving temperature of the troposphere (3–9 km) with the highest accuracy for the considered 1-week and 3-day measurement periods is determined for the IMCES lidar.