Tropospheric Gravity Waves Increase the Likelihood of Double Tropopauses

The tropopause region is crucial for the stratosphere-troposphere exchange (STE) and acts as an indicator of climate change. Double tropopauses (DTs) act to increase the STE process but their driving mechanisms remain an open question. The present assessment offers for the first time the linkage between tropospheric gravity waves (GWs) and DT events by exploring a global data set of multi-year radiosonde measurements. In the extratropics, the occurrence frequency of DT events keeps a remarkably consistent spatial-temporal structure with GW total energy. Under the DT scenario, GW total energy has increased by 37.67% compared to single tropopause events. Based on a statistical assessment, the upward propagating GWs throughout the second tropopause region can probably raise Kelvin-Helmholtz instability or turbulence, leading permanent irregularities in thermodynamic structure, and consequently, increasing the likelihood of DT. Atmospheric disturbances above the troposphere are predominantly associated with waves generated in the troposphere. Among others, gravity waves (GWs) play major roles in transport of energy and momentum from the lower to the upper atmosphere. The double tropopause (DT) caused by irregular temperature changes is a common phenomenon in the lowermost stratosphere, which has an indicative significance for climate change. The upward propagating GWs sourced from the troposphere can probably alter the temperature variability in the tropopause region, and therefore, they are likely associated with the occurrence of DTs. By analyzing a large amount of global radiosonde data, simultaneous measurements of tropospheric GWs and irregularities in the tropopause enable us to argue that GWs sourced from troposphere could increase the likelihood of DTs. A good level of agreement in spatial-temporal variability has been identified between Double tropopause (DT) events and tropospheric gravity wave (GW) total energySubstantial tropospheric GW and Kelvin-Helmholtz instability frequency enhancements in the tropopause region can be observed with DT phenomenaThe tropospheric GWs may increase the likelihood of DT events by introducing permanent localized irregularities or instabilities