Transport from convective overshooting of the extratropical tropopause and the role of large‐scale lower stratosphere stability

Abstract

Simulations of observed convective systems with the Advanced Research Weather Research and Forecasting (ARW‐WRF) model are used to test the influence of the large‐scale lower stratosphere stability environment on the vertical extent of convective overshooting and transport above the extratropical tropopause. Three unique environments are identified (double tropopause, stratospheric intrusion, and single tropopause), and representative cases with comparable magnitudes of convective available potential energy are selected for simulation. Convective injection into the extratropical lower stratosphere is found to be deepest for the double‐tropopause case (up to 4 km above the lapse‐rate tropopause) and at comparable altitudes for the remaining cases (up to 2 km above the lapse‐rate tropopause). All simulations show evidence of gravity wave breaking near the overshooting convective top, consistent with the identification of its role as a transport mechanism in previous studies. Simulations for the double‐tropopause case, however, also show evidence of direct mixing of the overshooting top into the lower stratosphere, which is responsible for the highest levels of injection in that case. In addition, the choice of bulk microphysical parameterization for ARW‐WRF simulations is found to have little impact on the transport characteristics for each case.

Numerical simulations of extratropical tropopause‐penetrating convection: Sensitivities to grid resolution

“…Figure shows that the domain‐averaged echo top in the model is largely biased low compared to observation. This result is comparable to that demonstrated in previous studies [e.g., Homeyer et al , ] and is likely due to limited representation of ice particle shapes and densities and differential sedimentation of precipitable particles in the BMP. However, the domain‐averaged cloud top is found to be 1.5–2 km higher than that observed by radar and is expected based on the limitations of the measurement, providing confidence in the representativeness of the simulated storms.…”

“…Many of these studies focus on individual cases of overshooting storms. Since direct measurement of convective overshoots is not possible with current research aircraft and alternative instrumentation, studies of tropopause‐penetrating convection in the extratropics with high‐resolution numerical models have also been common [e.g., Stenchikov et al , ; Gray , ; Wang , ; Mullendore et al , ; Lane and Sharman , ; Luderer et al , ; Chagnon and Gray , , ; Lane and Sharman , ; Homeyer et al , ; Bigelbach et al , ]. These modeling studies have identified important mechanisms for irreversible troposphere‐to‐stratosphere transport including gravity wave breaking and turbulent mixing.…”

The impact of overshooting deep convection on local transport and mixing in the tropical upper troposphere/lower stratosphere (UTLS)

“…Problems may arise due to prescribed aerosol loads acting as condensation nuclei which do not reflect actual aerosol amounts . Homeyer et al (2014) indicate that the vertical resolution of the meteorological input fields, particularly in the UTLS, can impact the model representation of the crosstropopause transport. Also, the horizontal resolution has been shown to be an important factor in order to resolve the convective processes (Bryan et al, 2003).…”

“…Folkins et al, 2002;Barth et al, 2007;Pommereau, 2010;Romps and Kuang, 2010), especially in the mid-latitudes (e.g. Wang, 2003;Hegglin et al, 2004;Mullendore et al, 2005;Homeyer et al, 2014), only few studies look at the downward transport of tracers triggered by convection (Lu et al, 2000;Hu et al, 2010;Barthe et al, 2011). However, these upper-level downdrafts, which are either direct convective downdrafts or related to gravity waves, may also transport dry and ozone-rich stratospheric air across the tropopause (Lu et al, 2000).…”

Microphysical Characteristics of Frozen Droplet Aggregates from Deep Convective Clouds

“…Vigorous turrets associated with deep convection generate intense precipitation that influences the hydrological cycle and large anvil shields that modulate radiation due to their extensive spatial and temporal coverage (Feng et al, 2011;Wang et al, 2015). Overshooting tops associated 15 with strong updrafts are responsible for stratosphere-troposphere exchange (Homeyer et al, 2014;Frey et al, 2015) and can be an indicator of a severity of thunderstorm (Proud, 2015).…”