Observation And Analysis Of Atmospheric Water Vapor Flux In Xi'an Area

Water vapor is one of the most dynamic components in the atmosphere.Water vapor flux,also known as water vapor transportation,is a very important water vapor parameter.It can represent both the intensity and direction of water vapor transportation.It has great scientific importance and research value to study the variation of water vapor and the law of water vapor transportation.Firstly,the paper studied the system correction method of Raman lidar.Based on the traditional calibration method of fixed-point radiosonde,the correction method based on the regression analysis in a fixed area is proposed.Combined with the data of radiosonde,the correction equation of lidar system in a best fixed area of 1-5km is obtained,which is w_cal=48.94386×w_lidar-0.28926.The correlation analysis results of the lidar data after calibration and the radiosonde data obtained the show that the linear correlation rate reaches 0.969,and the average relative error below 3km is less than 8.133%.It shows that the correction method of fixed area regression analysis is used to correct the atmospheric water vapor mixing ratio of Raman lidar.It is more conducive to the accurate detection of atmospheric water vapor mixing ratio.Using the Raman lidar water vapor detection system,the water vapor detection experiment and the result analysis over some areas in Xi'an are carried out.The atmospheric water vapor detection was carried out in the daytime and at night under sunny and cloudy weather conditions respectively,and the effective detection and inversion of atmospheric water vapor under 6km at night and 2.5km in day were realized.At the same time,the continuous observation experiments of atmospheric water vapor were carried out,and the mixing ratio of water vapor and specific humidity of the atmosphere were retrieved,and the characteristics of high spatial and temporal variation of atmospheric water vapor content were obtained.A Coherent Doppler wind lidar system was used to detect the atmospheric wind field,and the inversion of vertical and horizontal wind profiles below 3km was realized under different weather conditions.Then,combined with the Raman lidar system and the Doppler wind lidar system,a joint observation experiment is carried out to detect the atmospheric water vapor flux.The vertical and horizontal water vapor flux profiles and their temporal and spatial distribution characteristics under different weather conditions were obtained by using the synchronous atmospheric specific humidity profile and wind speed profile,and the HYSPLIT model was used to analyze the atmospheric water vapor transport.From the water vapor flux profile,it can be seen that the water vapor flux changes gently in sunny days,but more obviously in cloudy days,and the water vapor flux shows a great growth trend in a certain range above and below the clouds.Finally,according to the stratified variation characteristics of atmospheric water vapor flux,the data analysis and statistical average of the water vapor flux in different altitude layers are carried out.The results show that the water vapor flux in the upper clouds increases sharply before the rainfall,and the water vapor transport is enhanced,which provides strong water vapor transport for the subsequent rainfall.