Identification of Tropopause Height Using COSMIC-2 Occultation Atmospheric Refractivity

The radio occultation (RO) observation data provided by the second generation of The Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) were used to study and verify the method of determining the tropopause height based on atmospheric refractivity covariance transform. The principle of selecting the scale factor a in the atmospheric refractivity covariance transform is discussed based on the occultation events of GPS and GLONASS. It is found that the vertical variation of the refractivity in the lower troposphere region is smoother when a is taken as 30 km, and the prominent peaks of the refractivity profiles are more conducive to the determination of the tropopause. Comparing the atmospheric refractivity with the covariance-transformed atmospheric refractivity, it is found that the change of latter is more obvious and prominent, which can be used for the determination of the tropopause. According to the RO data in the low, middle and high latitudes, the tropopause heights obtained by the atmospheric refractivity covariance transform was compared with the cold point tropopause (CPT) and the temperature lapse rate tropopause (LRT) heights determined by the occultation temperature profile in the same occultation event, and the results show that there is a remarkable consistency between the three results at different latitudes, which means that the method used to determine the tropopause height after the covariance transformation of the atmospheric refractivity is feasible.