NWC REU 2016
May 23 - July 29



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Modeling the Physical, Dynamical, and Chemical Characteristics of Extreme Extratropical Convection in the Upper Troposphere and Lower Stratosphere

Russell Manser, Cameron Homeyer, and Daniel Phoenix


What is already known:

  • Convection that penetrates the tropopause transports gases into the stratosphere.
  • Numerical models can resolve gravity wave breaking and lofting of cirrus clouds in convection, which is a mechanism for transporting gases into the stratosphere.
  • Stratosphere-troposphere exchange impacts the chemistry of the upper troposphere and lower stratosphere, the radiation budget through modification of greenhouse gases and, in turn, climate.

What this study adds:

  • The ARW-WRF model coupled with chemistry is capable of simulating a real case of convection that penetrates the tropopause and has an above-anvil cirrus plume.
  • Numerical models can resolve the irreversible transport of trace gases into the stratosphere. While water vapor is enhanced at all levels the cloud reaches in the stratosphere, transport of carbon monoxide (a tropospheric pollutant) is limited to the maximum height of the simulated radar reflectivity echo top, which typically lies 2 km below the cloud top.


Stratosphere-troposphere exchange via extreme extratropical convection has implications for climate change. We test the ability of the ARW-WRF model to simulate the physical aspects of a real case of extreme extratropical convection that injected cloud particles into the stratosphere. We find that the model resolves storm structure sufficiently, and proceed to examine the representation of trace gas transport within the same case of convection. Additionally, distributions of trace gas concentrations across the nested model domain are considered in diagnosing irreversible transport. Trace gas transport is seen in model output within the cloud, but little evidence exists for out of cloud transport.

Full Paper [PDF]