Research On Doppler Wind Lidar System With Wind Detection Of High Temporal And Spatial Resolution

In recent year, middle upper atmosphere is paid much attention from those who relate to space science research and Geospace applicaition. and it is very important to know the atmosphere environment of this area. The distribution of wind field is one of the most important parameters to understand kinematics and dynamics of atmosphere. The aim of this research contains two aspects, one is offering reliable wind information for better understanding of atmospheric change regulation and local characteristic of space environment in lower stratosphere; the other is optimization of the compactness of lidar system and the key technique of frequency discrimination, therefore, it forms the foundation for the engineering of Doppler wind lidar.There are mainly four parts in this dissertation. The significance and ways of atmospheric wind detection, state of the art and basic priciple of wind lidar are introduced in the first two chapters. In the third chapter, the Doppler wind lidar for lower stratosphere and the promotion compared to the previous lidar are discripted, respectively.The efficiency of optical receiver is increased by expanding the area of telescope to a diameter of800mm. The detection and samping system is updated, as a result, the dynamic range of signal is increased by1-2orders. With all-fiber optical receiver, the system is of much more stability and easy adjustment. The temperature fluctuation around frequency discriminator and seeder, which would cause frequency drift, will be eliminated or relieved using a temperature chamber. The algorithms of wind retrieve results higher sensitivity, and thus the smaller error. After that, the the locking error of relative laser frequency is analyzed and it turns out to be the relative error of calibrated constant and the resolution of locking filter that affect. With the high accuracy measurement of calibrated constant by appling integrating sphere, the locking filter is optimaized and the corresponding locking error of laser frequency is calculated to be0.53m/s.The result of wind observation for lower stratosphere, which contains30-day data of horizontal wind profiles, is presented in chapter4. Comparison with radiosonde shows the average error of wind speed is1.5m/s with a deviation of 3.9m/s while the one for direction is-0.9°with a deviation of4.9°. Comparison with another wind lidar for15-60km is also made with good agreement at the overlap range. The comparison with radiosonde and lidar demonstrates the reliability of this lidar and the wind detection ranging from5km to35km with high temporal and spatial resolution.In the last chapter, the wind bias during wind observation is analyzed. The elements that cause the wind bias are seeder’s frequency and transmission of F-P interferometer. Theoretically, ambient temperature change of1K for FPI will causes the relative laser frequency drift of799MHz wihile the one for seeder laser is1650MHz. During the wind observation, temperature inside the chamber deviated relatively large because of the very low temperature outside. This would result that the locking of relative laser frequency can not match the frequency drift caused by temperature fluctuation. Therefore, the trend of radial speed drift is in accordance to the one of locking postion of FPI. At the end, a solution is proposed for the wind bias. Specifically, the null Doppler shift Rayleigh signal is coupled into the signal channels before atmospheric backscatter shot by shot. Therefore, the null-bias wind detection is performed by substracting the wind bias retrieved by the null Doppler signal from the one retrieved by backscatter using the same algorithm.