Extreme Altitudes of Stratospheric Hydration by Midlatitude Convection Observed During the DCOTSS Field Campaign

Water vapor's contribution to Earth's radiative forcing is most sensitive to changes in its lower stratosphere concentration. One recognized pathway for rapid increases in stratospheric water vapor is tropopause-overshooting convection. Since this pathway has been rarely sampled, the NASA Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) field project focused on obtaining in situ observations of stratospheric air recently affected by convection over the United States. This study reports on the extreme altitudes to which convective hydration was observed. The data show that the overworld stratosphere is routinely hydrated by convection and that past documented records of stratospheric heights of convective hydration were exceeded during several DCOTSS flights. The most extreme event sampled is highlighted, for which stratospheric water vapor was increased by up to 26% at an altitude of 19.25 km, a potential temperature of 463 K, and an ozone mixing ratio >1500 ppbv.

Automated summary

The concentration of water vapor in the lower stratosphere is the most sensitive factor contributing to Earth's radiative forcing. Rapid increases in stratospheric water vapor are often caused by tropopause-overshooting convection. This study focuses on obtaining in situ observations of stratospheric air affected by recent convection over the United States. The findings show that convective hydration routinely affects the stratosphere, with records of previous heights of convective hydration being exceeded during the DCOTSS flights. The most extreme event observed indicates a 26% increase in stratospheric water vapor at an altitude of 19.25 km, a potential temperature of 463 K, and an ozone mixing ratio >1500 ppbv.