Saturation correction near the ground for pure rotational Raman lidar

Saturation correction for photon counting near the Earth's surface can improve the accuracy of temperature measurement in the troposphere by pure rotational Raman lidar (PRRL). The PRRL system uses a 532-nm band as a light source, and the echo signals of high-J and low-J channels separated by a double grating monochromator are used for temperature profile inversion. The pulse-height distribution and the discriminator level selection in the system, which comprise a photomultiplier and a photon counter, saturate photon counting near the ground and affect the echo signals from the higher layer for calibration. Given its nonlinear effect on the photomultiplier tubes, the correction method is applied to the echo signals of the calibration interval in troposphere temperature measurements. The method not only reduces the error in temperature measurement (the root-mean-square error of temperature reaches 1.5 K), but also accurately indicates the distribution of the inversion layer within the boundary layer. It can be applied to deal with the saturation phenomenon of a photomultiplier tube.