The high spatial and temporal resolution observations of the middle and upper atmosphere can promote the study of atmospheric circulation coupling mechanisms and improve the accuracy of medium- and long-term weather forecasting. The Rayleigh Doppler lidar (RDLD) is able to detect atmospheric temperatures and wind speeds above 30 km altitude. However, the signal-to-noise ratio of the high-altitude Rayleigh backscatter signal received by RDLD is extremely low. To ensure measurement accuracy, it is normally required to increase the measurement spatial and temporal resolution, as well as to optimize the signal transceiver efficiency of the lidar system. Doppler shift wind speed measurement requires high frequency stability of the emitted laser, and the output frequency of the traditional seed injection laser cannot be kept strictly the same as the seed laser. In this paper, a new RDLD is designed using a new seeder multi-stage series direct amplification multiplier laser and a polarization-splitting-based time-division multiplexing transmitter system. The problems of long integration time and unstable laser frequency consistent with existing RDLD are solved. Higher spatial and temporal resolution atmospheric temperature and wind speed measurements are obtained.

The system is equipped with a new laser system to output high repetition frequency and high energy pulsed laser. The laser is emitted into the atmosphere in vertical, westward, and northward directions in sequence by a polarization-splitting-based time-division multiplexing transmitter system. The atmospheric Rayleigh backscatter signal is coupled into a multimode fiber by the receiving telescope, combined into one way by a 3-in-1 optical fiber and sent into a iodine cell frequency discriminating receiver for atmospheric wind speed and temperature measurements. The simulation method is used to calculate the expected detection performance of the new RDLD design, and verify the feasibility of the new design. Finally, we built a set of RDLD according to the new design. The real atmospheric echo signal, atmospheric temperature and wind speed measurement results are obtained through the observation experiments. The real performance of the new RDLD system will be analyzed by comparing with the simulation results, and the accuracy of the measurement results will be confirmed by comparing with the atmospheric model and satellite measurement results.

The simulation results of the new RDLD in Fig. 8 show that it can achieve simultaneous measurements of atmospheric temperature and zonal and meridional horizontal wind speed with a temporal resolution of 30 min and vertical distance resolution of 1 km. The detailed conditions of an integration time is 5 min for the vertical channel and 12.5 min for other two inclined channels. The theoretical measurement uncertainty of atmospheric temperature at 60 km altitude is 1.99 K, and the theoretical measurement uncertainty of zonal and meridional horizontal wind speed is 4.78 m/s. In the observation experiment (Fig. 9), the actual average measurement uncertainty of the atmospheric temperature of the new RDLD is 2.539 K, and the actual average measurement uncertainty of the zonal and meridional horizontal wind speed is 2.972 m/s and 2.575 m/s, respectively. The zonal and meridional horizontal wind speed average measurement result differs from the average model result by -2.327 m/s and -3.946 m/s in the altitude range from 30 km to 50 km, and the temperature average result differs from the average model result by 1.137 K (Fig. 10). In the altitude range from 50 km to 70 km, the zonal and meridional horizontal wind speed deviation increases to -5.904 m/s and -12.703 m/s, and the temperature deviation increases to 1.447 K. The difference between RDLD measurement and satellite measurement is 2.889 K and 4.038 K in the altitude ranges of 30-50 km and 50-70 km, respectively.

The proposed Rayleigh Doppler lidar applies a seeder multi-stage series direct amplification multiplier laser system for ground-based mid-atmosphere detection. The laser system provides high-frequency stability, high laser repetition frequency and high single pulse energy laser output through direct power amplification of the seeder by a multi-stage fiber amplifier and solid-state amplifier. The laser atmospheric echo signals received in three directions are combined by a 3-in-1 optical fiber and sent to the same set of iodine cells for Doppler discriminations, the wind speed measurement uncertainties introduced by calibration differences of multiple channels can be avoided. The simulations and experiments have shown that it can solve the problem of too-long signal integration. The polarization-splitting-based time-division multiplexing transmitter reduces the overall system's complexity. Experimental results demonstrate that the actual signal transceiving capability and measurement performance of the system have been close to that expected in theoretical simulation. After that, simultaneous measurements of atmospheric temperature and horizontal wind speed at vertical distance resolution of 1 km and time resolution of 30 min are obtained. The accuracy of the new RDLD measurement results is validated by the good agreement with the European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric model and Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite measurements.