Fifteen-years of Tropopause Altitude monitoring by GNSS Radio Occultation Measurements

Abstract

<p>Tropopause altitude variability can be considered one of the most effective indicator  of climate changes.  In particular with warming/cooling of the troposphere, it works as  the mercury vertical column in an old analogic thermometers. Besides, tropopause location affects the stratosphere–troposphere energy and matter exchange,through  the overshooting of  the water vapor from the troposphere to the  stratosphere occurring in particular  at tropical latitudes. So, the monitoring of tropopause altitudes and determination of possible local/global trends, are extremely important for climate investigations.</p><p>In this work we plan to estimate and monitor tropopause altitudes on global scale for a period ranging from 2007 up to 2021, by processing millions of  GNSS Radio Occultation (RO) observations stacked thanks to  COSMIC (I & 2) FORMOSAT missions. An analysis over such time scale could be very helpful to understand the long periodic climate trends of Earth. For this task we apply    four different tropopause altitude definitions: the Lapse Rate Tropopause (LRT), the Cold Point Tropopause (CPT), a weak form of LRT as defined in (Andrisani & Vespe, 2021), and the tropopause altitude defined by (Vespe at al., 2017), based on the detections of bumps in bending angle (BA) profiles. This last definition could be more easily applied  than the LRT or the CPT , because  BA are raw data of level 1 provided by RO, while  temperature profiles are data of level 3  and   require additional assumptions and  , in somehow, a  more problematic modeling.</p>