Upper Troposphere and Lower Stratosphere Break out Chairs: Laura Pan and Mark Zondlo Contributors: Alan Fried, Sue Schauffler, Andreas Fix, Steve Cohen, …

Upper Troposphere & Lower Stratosphere - A region of coupled dynamics, chemistry and cloud microphysics

A Set of Inter-Related Problems Chemistry-climate interaction Water vapor, ozone, clouds and aerosols - species of significant climate impact Transport and mixing - dynamical processes of a range of scales (planetary - synoptic - meso) Transformation- Multi-phase chemistry and cloud microphysics

What controls the tropopause temperature What controls the tropopause temperature? Competing Hypos: the tropical tropopause T is driven by the large scale dynamics, Extratropical forcing (EP flux) vs. tropical wave (convection)? Need better wind data in the UT

Theories of Dehydration Convective Dehydration Sherwood and Dessler, GRL, 27, 2513-2516, 2000; JAS, 58, 765-779, 2001. Two current theories of dehydration “cold trap” dehydration: air detrains near the bottom of the TTL, moist relative to the stratosphere. It then slowly ascends. As it does, some in situ process dehydrates it. Because the tropopause is the coldest point in the temp profile, the trop temp sets the amount of water vapor entering the strat. Conceptually appealing, model by holton and gettelman gets realistic water vapor profiles Convective dehydration: air detrains throughout the TTL, with air detraining at higher altitudes being much drier. This air then ascends into the stratosphere. There’s a recent paper by Steve Sherwood and myself showing that this theory fits the observations. Both theories decouple STE w/ dehydration “Cold Trap” Dehydration Holton and Gettelman, GRL, 28, 2799-2802, 2001.

Water vapor Facilities Needs: in-situ isotopes (HDO, H2O-18) profiling of hydrometeors (phase) and updraft velocities from aircraft in-cloud, near-cloud fast temperature other Critical need for calibration facility under known conditions climate observation network for reference sensor, long-term history

Dynamic Coupling of stratosphere and troposphere: Tracer-correlation as a tool for constrain new generation of Chemistry-climate models

Profiling capability Dynamic parameters: ground based and airborne radars, winds, T profilers Chemical transport tracers: LIDAR for both ozone and water vapor,

DLR H2O DIAL on Falcon water vapor curtain q (g/kg) R west east

UTLS Chemical Processes Lower Stratosphere RO2 or HOx NOx CH2O H2O2 CH3OOH CH3C(O)CH3 O3 Upper Troposphere Entrainment-Detrainment Mid-Troposphere Re-evaporation Schematic diagram of Processes relevant to chemistry in the Upper Troposphere/Lower Stratosphere Region Boundary layer species (including urban emission, biogenic emissions, biomass burning emissions, marine emissions) can be drawn into Cb cloud base. Species move through the cloud and encounter other species in the gas phase as well as in the condensed phase (liquid water and ice) which may transform the species. Species may be entrained and/or detrained throughout the cloud (a “leaky pipe”). Species in the liquid phase may rainout; rain may evaporate and redistribute species in the mid-troposphere or elsewhere. NOx (and possibly other species) is produced from lightning that can lead to perturbations of the chemistry. Species (including HOx precursors) are ejected from the cloud at high altitudes; gas phase chemical processes are potentially perturbed by these species – perturbations that can remain for perhaps days after the transport. Upper tropospheric chemistry including HOx budgets and aerosol formation and growth may be impacted by these convective processes. Pilot studies have examined some of these processes (STERAO), which demonstrated some of the tools needed for such studies, including the need for a well-equipped high altitude aircraft platform (such as HIAPER or the WB-57). Successful new science will come from use of multiple observational and numerical model tools. This is not meant to describe convection in detail, but only point out those issues related to UTLS chemistry. Scavenging & rainout Boundary Layer UTLS Chemical Processes

Ozone and convective cloud chemistry Radical measurements: in situ HOx, Nox (in development) fast VOC measurements (fast formaldehyde, methanol, acetone, peroxides, formic acid, etc. - 1-10s of seconds) (has gaps) fast inorganic bromine and iodine

Other facility needs inlet testing facility (aerosols, reactive gases, adsorption, evaporation, etc.) climate observation network (UT/LS water vapor and trop. ozone trends) calibration facilities, intercomparisons, airflow studies Lagrangian ballon exp. in UT/LS Dense network balloons vs. aircraft studies Improved capabilities to track urban, biomass plumes spatial and temporal