Identification of the tropopause height using the covariance transform method from GPS radio occultation bending angles

This paper focuses on the study of the covariance transform method used to identify the tropopause height directly from bending angle profiles of GPS radio occultation (RO) observations. The principle of this method is introduced and the choice of scale factor ais discussed. Different values of scale factor a are tested and it is found that a=35 km is the optimal choice which can identify the larger scale tropopause transition and filter small scale variations associated with lower troposphere temperature and humidity gradients. The tropopause height determined with the covariance transform method is compared with the lapse rate tropopause (LRT) and the cold point tropopause (CPT) determined from the temperature profiles of the corresponding RO events, as well as with the LRT and the CPT derived from the radiosonde observations occur within 3 hours and 300 km of the RO events. The results show that this method is feasible to identify the tropopause directly from the bending angle profiles of GPS RO observations and it performs even better than other ways over high latitude regions.