Trace gas transport in the vicinity of frontal convective clouds

Abstract

Airborne measurements of NOx, NOy, CO, and O3 were conducted in the vicinity of a line of towering cumulus and cumulonimbus clouds (approximate altitude, 9 km) in south‐central Oklahoma, on the afternoon of June 17, 1985. NOx, NOy, and CO concentrations in the upper tropospheric outflow region of these clouds were near environmental levels. Meteorological analyses show that these clouds were located above a cold front, which prevented the entry of air from the boundary layer directly below and near the cloud. Examination of the [NOy]/[CO] and [NOx]/[CO] ratios, as well as determination of the lifting condensation level and other thermodynamic analyses, indicated that the most likely origin of the air in the cloud outflow region was the layer immediately above the top of the boundary layer, which was quite clean. It appears that very little NOy was available to be scavenged by the clouds. The results for this case suggest that the large amount of vertical trace gas transport that has been noted in previous observations and model results cannot simply be extrapolated to all convective cells. The results also show the usefulness of CO as a conserved tracer.

Evidence of the impact of deep convection on reactive Volatile Organic Compounds in the upper tropical troposphere during the AMMA experiment in West Africa

“…In the last two decades, some observational campaigns have been conducted worldwide to better understand the role of deep convection and its efficiency to transport gaseous species from the boundary layer to the upper troposphere (UT). Many studies over midlatitudes (Dickerson et al, 1987;Hauf et al, 1995;Pickering et al, 1988) showed that deep convection could pump low tropospheric air to the tropopause region and proved effective transport of trace gases (e.g. CO, O 3 ; Ström et al, 1999;Fischer et al, 2003) even highly reactive and short-lived (e.g.…”

Relationship between level of neutral buoyancy and dual-Doppler observed mass detrainment levels in deep convection

“…The most efficient method for transporting heat, moisture, and chemical tracers from the boundary layer to the upper troposphere and lower stratosphere is through moist convection (e.g., Dickerson, 1987;Pickering et al, 1988;Mullendore et al, 2005) . Deep convection allows constituents from the boundary layer to be transported within tens of minutes into the upper troposphere and lower stratosphere, where longer chemical residence times can increase their impact on the radiative budget, and higher wind speeds can increase their influence region from local to regional or even global (e.g., Dickerson, 1987;Pickering et al, 1993;Thompson et al, 1997).…”

Deep convective injection of boundary layer air into the lowermost stratosphere at midlatitudes

“…Large scale mixing of pollution throughout the troposphere is accomplished by frontal activity (e.g. Bethan et al, 1998;Fischer et al, 2002) and deep convection, a particularly efficient process for fast Correspondence to: H. Fischer (hofi@mpch-mainz.mpg.de) transport of boundary layer air into the upper troposphere (Dickerson et al, 1987;Pickering et al, 1988;Hauf et al, 1995;Ström et al, 1999). Tropospheric air enters the stratosphere predominantely in the tropics as part of the large scale Brewer-Dobson-circulation (Holton et al, 1995), with a small contribution from deep convection penetrating the tropical tropopause (Danielsen, 1982(Danielsen, , 1993.…”