The tropical tropopause layer (TTL) is a gateway of air and equatorial waves entering the stratosphere. Waves propagating through the TTL to the stratosphere contribute to driving the mean tropical upwelling and quasi-biennial oscillation (QBO) of stratospheric wind. The chemical and physical processes in the TTL determine transport of atmospheric constituents into the stratosphere. Wave-induced temperature variations affect TTL cloud formation that regulates water vapor and ozone depleting substances entering the stratosphere. Cirrus clouds and stratospheric water vapor, together with their influence on stratospheric ozone chemistry, have significant impacts on the global radiation budget. Therefore, proper representations of TTL waves in climate models will be critical to simulate stratospheric water vapor, cirrus clouds in the TTL, and wave-driven mean circulation.

Here we will present characteristics of waves in the TTL observed in radiosondes, COSMIC GPS, and NASA’s aircraft measurements during the Airborne Tropical TRopopause Experiment (ATTREX) mission. The ATTREX data include temperatures and cirrus clouds, providing useful information on how waves affect cirrus occurrence in the TTL. The measurements show that cirrus clouds preferentially exist in cold temperature anomalies (T’<0) in addition to the importance of cooling (dT’/dt). We will show that thin layers of cirrus clouds are highly related to vertical structures of waves. Vertical wavelet analysis with radiosondes and GPS reveals that a significant wave spectrum is contributed by shallow waves at vertical wavelengths shorter than ~3 km, scales that current climate and (re)analysis models cannot resolve due to limited vertical resolution. Our results suggest that coarse vertical resolution of current climate models will underrepresent the wave impacts on the TTL process es and their feedback, and will prohibit proper propagation of waves into the stratosphere.

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*email: jieunk@colorado.edu
*Preference: Oral