[A-AS09] [EE] Stratosphere - Troposphere Interaction

[AAS09-21] Is convection important for controlling stratospheric humidity?

*Rei Ueyama¹, Mark Schoeberl², Eric Jensen¹, Leonhard Pfister¹, Melody Avery³ (1.NASA Ames Research Center, 2.Science and Technology Corporation, 3.NASA Langley Research Center)

Keywords:tropical tropopause layer, water vapor, cirrus clouds, stratosphere, convection, climate

We investigate the role of convection on stratospheric water vapor and upper tropospheric cloud fraction using two sets of complementary transport and microphysical models driven by MERRA-2 and ERA-Interim meteorological analyses: (1) computationally efficient ensembles of forward trajectories with simplified cloud microphysics, and (2) one-dimensional simulations with detailed microphysics along back trajectories. Convective influence along the trajectories is diagnosed based on TRMM/GPM rainfall products and geostationary infrared satellite cloud-top measurements, with convective cloud-top height adjusted to match the CloudSat, CALIPSO, and CATS measurements. We evaluate and constrain the model results by comparison with satellite observations and high-altitude aircraft campaigns (e.g., ATTREX, POSIDON).

Convection moistens the lower stratosphere by approximately 0.6 ppmv (about 15% increase) and increases the cloud fraction in the upper troposphere by roughly 15%. Convection moistens the upper troposphere and lower stratospheric region mostly by saturating the convectively-influenced parcels. Including lofted ice in the microphysics has a negligible impact on lower stratospheric humidity. The highest convection has a disproportionately large impact on stratospheric water vapor enhancement. Implications of these model results on the role of convection on present and future climate will be discussed.