On the origin of pronounced O₃ gradients in the thunderstorm outflow region during DC3

Abstract

Unique in situ measurements of CO, O3, SO2, CH4, NO, NOx, NOy, VOC, CN, and rBC were carried out with the German Deutsches Zentrum für Luft‐ und Raumfahrt (DLR)‐Falcon aircraft in the central U.S. thunderstorms during the Deep Convective Clouds and Chemistry experiment in summer 2012. Fresh and aged anvil outflow (9–12 km) from supercells, mesoscale convective systems, mesoscale convective complexes, and squall lines were probed over Oklahoma, Texas, Colorado, and Kansas. For three case studies (30 May and 8 and 12 June) a combination of trace species, radar, lightning, and satellite information, as well as model results, were used to analyze and design schematics of major trace gas transport pathways within and in the vicinity of the probed thunderstorms. The impact of thunderstorms on the O3 composition in the upper troposphere/lower stratosphere (LS) region was analyzed. Overshooting cloud tops injected high amounts of biomass burning and lightning‐produced NOx emissions into the LS, in addition to low O3 mixing ratios from the lower troposphere. As a dynamical response, O3‐rich air from the LS was transported downward into the anvil and also surrounded the outflow. The ΔO3/ΔCO ratio was determined in the anvil outflow region. A pronounced in‐mixing of O3‐rich stratospheric air masses was observed in the outflow indicated by highly positive or even negative ΔO3/ΔCO ratios (+1.4 down to −3.9). Photochemical O3 production (ΔO3/ΔCO = +0.1) was found to be minor in the recently lofted pollution plumes. O3 mixing ratios within the aged anvil outflow were mainly enhanced due to dynamical processes.

Aerosol characteristics and particle production in the upper troposphere over the Amazon Basin

“…The precision of the O 3 measurements is 2 % or 1 ppb, whichever is larger; the accuracy is 5 %. Details on the use of this instrument can be found in Huntrieser et al (2016).…”

Introduction to the Deep Convective Clouds and Chemistry (DC3) 2012 Studies

“…Measurements found stratospheric ozone mixing into storm anvils (Huntrieser et al, ; Schroeder et al, ) and even wrapping around the anvil in one case (Pan et al, ), bringing high ozone concentrations into the upper troposphere. Analysis of aged convective outflow air revealed enhanced ozone mixing ratios by 20–50 ppbv mainly from dynamical processes (Huntrieser et al, ). Although we expect ozone to be formed in the upper troposphere convective outflow plumes, transport of ozone from the stratosphere also contributes to increased upper troposphere ozone mixing ratios, and this dynamical process needs to be better represented in chemistry transport models.…”

A cloud-ozone data product from Aura OMI and MLS satellite measurements

“…The enhanced ozone over southern Africa suggests that ozone produced from regional pollution including biomass burning, which is largest around SeptemberOctober each year in the Southern Hemisphere, reaches the upper regions of the clouds. However, the regional elevated ozone over southern Africa may be caused by other sources including lightning NO x , transport by the Walker circulation, and mixing of stratospheric air that is transported into the troposphere in response to cloud tops overshooting the tropopause (e.g., Huntrieser et al, 2016, and references therein). The low ozone VMR in the western Pacific in Fig.…”

“…Huntrieser et al (2016, and references therein) combined aircraft and cloud measurements with a model to study ozone distributions and sources associated with deep convective clouds over the central US. Huntrieser et al (2016) identified upward transport of lower tropospheric ozone and ozone precursors into the upper troposphere within thick clouds.…”

“…Huntrieser et al (2016, and references therein) combined aircraft and cloud measurements with a model to study ozone distributions and sources associated with deep convective clouds over the central US. Huntrieser et al (2016) identified upward transport of lower tropospheric ozone and ozone precursors into the upper troposphere within thick clouds. They also showed that cloud tops overshoot the tropopause and inject high amounts of biomass burning pollutants (largely CO and NO x ) and lightning-produced NO x into the low stratosphere, while at the same time ozone-rich air from the low stratosphere is transported downward into the cloud anvil and surrounding outflow regions as a dynamical response to overshooting.…”