Using Fengyun 3C Occultation Data To Analyze The Variation Characteristics Of Tropopause Parameters In China

Since the 21 st century,Global Navigation Satellite System(GNSS)Radio Occultation technology has become more mature and widely used in atmospheric sounding.This technology uses the signal delay between GNSS and LEO satellites to invert the global high-precision atmospheric profile parameters.Therefore,GNSS radio occultation technology has important application prospects in atmospheric sounding and weather forecasting.The tropopause is the transition region between the troposphere and the stratosphere.In the tropopause,the stratosphere and troposphere exchange water vapor,energy,etc.frequently,which can provide physical and chemical boundary conditions for the air from the troposphere to enter the stratosphere.The spatial distribution and temporal variability of atmospheric parameters at the tropopause have important implications for global climate change and energy changes.Traditional observation techniques have high cost and low resolution,while GNSS radio occultation technology has many advantages and scientific significance for studying the tropopause.This paper estimates and studies the tropopause variation in China from 2015-2019 based on FY-3C GNSS radio occultation observations.Firstly,the GNSS radio occultation technique is introduced,and the quality of FY-3C radio occultation data is analyzed,and finally the spatial and temporal variation characteristics of the tropopause structure in China are analyzed using the FY-3C radio occultation data.The main results of this paper are summarized as follows:(1)The FY-3C radio occultation data products are examined using COSMIC occultation products,global radiosonde data,and ECMWF products.The results show that the detection capability is significantly enhanced for FY-3C GNOS detectors with dual systems,and their data products have high reliability.(2)The spatial resolution of 2°×2° is used to divide the whole Chinese region into 608 grids,and then the number of occultation profiles in each grid is counted.The LRT(Lapse Rate Tropopause)and CPT(Cold Point Tropopause)algorithms are used to calculate the tropopause parameters respectively,which are compared with the global radio sounding data and the ECMWF product,and the results show a good agreement.(3)More than 500,000 FY-3C GNSS Radio Occultation profiles from 2015 to 2019 are used to calculate the relevant tropopause parameters in China.It is found that the structure of the tropopause parameters has obvious latitudinal distribution and seasonal variation characteristics.The median slope regression method is used to study interannual variations of the tropopause parameters.The tropopause height increases by 0.046 km,the tropopause temperature decreases by 0.07 K,and the pressure decreases by 0.96 mbar per year on average in the study period of 2015-2019 in the Chinese region.