Ground-based GPS ZTD Data Quality Control And Assimilation Application In East China Regional Model

Water vapor observations are important for numerical prediction.The Zenith Total Delay(ZTD)of the Global Positioning System(GPS)can reflect the a tmospheric water vapor content,which has an important supplementary role in water vapor observation.The quality control and assimilation application in numerical mode of GPS ZTD data have important practical significance.In this paper,a series of quality control processes are established for the ground-based GPS ZTD data,and the observation errors of the GPS ZTD data are counted and assimilate the data in numerical mode.The main findings are as follows:Quality analysis of ground-based GPS ZTD data: The quality analysis of the ground-based GPS ZTD is performed in terms of missing,solving errors and bias.The analysis results show that there is a certain lack of measurement at the national GPS ZTD stations and it is more serious in stations in the Northeast region.The GPS ZTD data of Liaoning Province is decoded by Liaonin g and and there is almost no missing data.Therefore,the ZTD data decoded by Liaoning Province can complement the missing data in Northeast China.The average settlement error is below 16 mm and the settlement error in the Southe ast station is relatively small.Stations in the southeast region are dominated by positive bias while other regions are dominated by negative bias.Quality control quantity control of ground-based GPS ZTD data: As eries of quality control processes were established for ground-based GPS ZTD data,and the quality of the data before and after quality control was compared.The quality control process mainly includes site height difference check,stability check,extreme value check,double weight check,deviation correction,standard deviation check and space thinning.The quality comparison results of the data before and after the quality control show that the standard deviation,deviation,and Gaussian distribution of the GPS ZTD data are significantly improved after the quality control.Observation error estimation of ground-based GPS ZTD data in East China: For the East China regional model and GPS ZTD data,the method proposed by Holliswort in 1986,the method proposed by Desroziers G in 2001,the method proposed by Desroziers G in 2005 and the monthly maximum OMB standard deviation method were used to calculate the observation errors of GPS ZTD data.The results show that the the first three statistical methods of observation error are approximately 0.8cm,while the result of the last method is 1.99 cm.Therefore,0.8cm is used as the observation error of GPS ZTD data for the East China Regional Model.Ground-based GPS ZTD data assimilation experiment: Based on the East China regional numerical prediction model,GPS ZTD data assimilation tests were performed for the 2019 super typhoon "Lekima" and the effect of GPS ZTD data assimilation on the typhoon "Lekima" was studied.The results of the incremental analysis from the assimilation of GPS ZTD data show that the assimilation of GPS ZTD data can have an effect on the water vapor and temperature of the initial field,of which the effect on water vapor is the largest,and it can affect the circulation field after the cycle assimilation.Precipitation prediction results show that GPS ZTD assimilation can improve the location and intensity of typhoon precipitation.