Convective transport of water vapor into the lower stratosphere observed during double-tropopause events

Abstract

We present in situ observations of convectively injected water vapor in the lower stratosphere from instruments aboard two aircraft operated during the Deep Convective Clouds and Chemistry experiment. Water vapor mixing ratios in the injected air are observed to be 60–225 ppmv at altitudes 1–2 km above the tropopause (350–370 K potential temperature), well above observed background mixing ratios of 5–10 ppmv in the lower stratosphere. Radar observations of the responsible convective systems show deep overshooting at altitudes up to 4 km above the lapse rate tropopause and above the flight ceilings of the aircraft. Backward trajectories from the in situ observations show that convectively injected water vapor is observed from three distinct types of systems: isolated convection, a convective line, and a leading line‐trailing stratiform mesoscale convective system. Significant transport of additional tropospheric or boundary layer trace gases is observed only for the leading line‐trailing stratiform case. In addition, all observations of convective injection are found to occur within large‐scale double‐tropopause events from poleward Rossby wave breaking. Based on this relationship, we present a hypothesis on the role of the large‐scale lower stratosphere during convective overshooting. In particular, the reduced lower stratosphere stability associated with double‐tropopause environments may facilitate deeper levels of overshooting and convective injection.

Long-range transport pathways of tropospheric source gases originating in Asia into the northern lower stratosphere during the Asian monsoon season 2012

“…Therefore, the spatial structure of young air masses characterized by enhanced values of emission tracers from India/China resembles a bubble within the upper troposphere. These air masses are transported eastwards along the subtropical jet and most likely enter the extratropical lower stratosphere driven by Rossby wave breaking events associated with double tropopauses (e.g., Vaughan and Timmis, 1998;Castanheira and Gimeno, 2011;Ungermann et al, 2013;Homeyer and Bowman, 2013;Homeyer et al, 2014). Our simulations show that after entering the lower stratosphere, these air masses are mixed irreversibly with the surrounding stratospheric air.…”

“…Previous studies also found intrusions of tropospheric air into the lower stratosphere associated with extratropical double tropopauses (e.g., Pan et al, 2009;Homeyer et al, 2011;Vogel et al, 2011b;Schwartz et al, 2015;Wu and Lü, 2015). Further, it was shown that double tropopauses are frequently associated with Rossby wave breaking events along the subtropical jet (e.g., Vaughan and Timmis, 1998;Castanheira and Gimeno, 2011;Ungermann et al, 2013;Homeyer and Bowman, 2013;Homeyer et al, 2014).…”

“…In addition to this large-scale transport process of water vapor by air mass exchange between the tropics and the extratropics, convection-induced injections of water vapor in midlatitudes can also occur in large storm systems such as tropical cyclones and by deep continental convection (e.g., Anderson et al, 2012;Homeyer et al, 2014;Vogel et al, 2014).…”

The Deep Convective Clouds and Chemistry (DC3) Field Campaign

“…lofting biomass-burning plumes, penetrating into the lowermost stratosphere, and generating stratospheric intrusions along the sides of storms. Additional studies show that the aircraft data, especially the DC-8 lidar data, provided unique depictions of convectiveinduced mixing between the stratosphere and troposphere, via both direct injections of water into the stratosphere (Homeyer et al 2014) and wrapping of stratospheric air around the anvil of storms (Pan et al 2014). The DC3 data are also being analyzed to characterize different anthropogenic and biogenic sources of volatile organic compounds and the tropospheric distribution of aerosol composition, including brown carbon (Liu et al 2014).…”

Composition and Thermal Structure of the Upper Troposphere and Lower Stratosphere in a Penetrating Mesoscale Convective Complex Determined by Satellite Observations and Model Simulations

“…This topic has attracted much recent attention with the development of satellite observations [1][2][3][4][5][6]. Penetrating mesoscale convective complexes (MCCs) are deep convective systems that have important effects on stratospheric-tropospheric exchange and the structure of the upper troposphere and lower stratosphere.…”