Analysis Of Tropospheric Delay And Water Vapor Content Using GPS During Fog And Haze

In recent years,the serious haze weather has appeared in many big cities in China.The content of contaminated particles(PM2.5)in air is the key indicator of haze.A sharp rise of the content of PM2.5 in the air will appear during haze formation period.The hydroscopicity of air suspended particles makes both the tropospheric delay and moisture content changes.Then,in the haze weather,the accurate detection of tropospheric delay and moisture content in the atmosphere may have a certain directive effect on the monitoring of haze weather..The traditional tropospheric atmosphere detection methods have weakness of low temporal and spatial resolution and high price,while the rise of ground-based GPS/GNSS meteorology can provide real-time,high-precision,high spatial and temporal resolution of tropospheric delay and moisture content monitoring in near-earth space.rise of the foundation GPS/GNSS meteorology can provide real-time,high precision and high temporal spatial resolution for the troposphere delay and water vapor content in the near earth space.Therefore,this paper uses PM2.5 data and GPS observational data to study the change of GPS tropospheric delay and water vapor content in haze weather,analyzing the regularity of time series change in haze weather,then provide certain reference for the formation and prediction of haze weather.The main contents and results are as follows:1)We systematically studied the method of using ground-based GPS to inverse the precipitable water.By analyzing the effect of GMF,VMF1 and NMF in actual data processing,we found that the difference among the three in actual data processing is not obvious.2)We selected the PM2.5 data from January 2014 to February 2014 and the data of the BJFS,CHAN,SHAO stations provided by the National Center for Atmospheric Research(NCAR).(NCAR can provide the troposphere and precipitable water data with 2-hour resolution of IGS stations),analysis of the change trend of ZTD,ZWD and PWV in the three stages of haze occurrence,duration and dissipation during severe haze weather in the two months.The results show that ZTD,ZWD and PWV are in good agreement with the change trend of PM2.5,but the time and stop time of the change are not necessarily synchronized.Heavy haze has a positive effect on maintaining high levels of ZTD,ZWD and PWV.3)We selected the GPS data of BJFS station January,February,June,July,November and December 2015,and calculated the ZTD,ZWD and PWV through GAMIT solution.Analyzing the haze weather according to the historical weather.It is concluded that severe haze weather has an impact on ZTD's changes,and higher PM2.5 can help ZTD maintain a higher value.In summer,strong convective weather has created diffusion conditions for atmospheric pollutants,and frequently rainfall.So that in some frequent rainfall period the tendency of PM2.5 and ZWD has no obvious consistency,which is mainly reflected in the continuous maintenance of PM2.5 at low levels while ZWD fluctuates repeatedly,and the extremely short time precipitation weather will reduce a small amount of ZWD.It will definitely lead to a significant decrease in PM2.5.In spring,autumn and winter,high value PM2.5 does not necessarily occur with high value ZWD,and the obvious change of PM2.5 will be consistent with the change trend of ZWD in most cases.4)We selected the 2015 BJFS station for a number of short-term periods(3-7 days)to analyze the change of PWV in haze weather and the analysis of the correlation between PWV and PM2.5.The conclusion is that there is a certain correlation between PWV and PM2.5,but the correlation coefficient is unstable,the correlation coefficient is also higher when there is a significant change between PM2.5 and PWV.And PM2.5 values remain very low,when the correlation between PWV and PM2.5 is low.The correlation coefficient is obviously different from the selection of experimental data,and there is no general rule,therefore the ground-based GPS can not be used as a perfect method of haze monitoring.