Heidi Huntrieser

Transport and production of NO X in electrified thunderstorms: Survey of previous studies and new observations at midlatitudes

First airborne NOx (NO+NO2) measurements in anvils of active thunderstorms in Europe were performed in summer 1996 over southern Germany and Switzerland (47°-49°N). This field experiment LINOX (lightning-produced NOx) was designed to study the production of NOx by lightning discharges and the transport in convective storms. With the research aircraft Falcon of the Deutsches Zentrum fur Luft- und Raumfahrt, about 20 anvil penetrations were performed including measurements of NO, NO2, CO2, O3, and meteorological parameters. In thunderstorm anvils, mean NOx mixing ratios between 0.8 and 2.2 ppbv were measured with peak values reaching up to 4 ppbv. A considerable part of these enhancements could be attributed to the transport of polluted air from the planetary boundary layer (PBL) using CO2 as tracer for PBL air. NOx produced by lightning can be obtained by subtracting the fraction of NOx transported from the PBL from total NOx measured in the anvil. The NOx/CO2 correlation in larger cumulus clouds without lightning was used as reference for the transport of PBL air in the anvils. In smaller LINOX thunderstorms the contribution from lightning, respectively, PBL transport to anvil NOx, was about equal. However, in medium and large LINOX thunderstorms the contribution from lightning dominated (60–75%). For these kind of thunderstorms it was estimated that ∼1.0±0.5 ppbv NOx resulted from lightning production. The observations were used to quantify the NOx production per thunderstorm and to give a rough estimate of the annual production of NOx. For the global lightning nitrogen budget the uncertainties were considerable (0.3–22 Tg(N) yr−1). The mean value for the global NOx production rate by lightning in the upper troposphere was estimated to 4 Tg(N) yr−1.

The Deep Convective Clouds and Chemistry (DC3) Field Campaign

AbstractThe Deep Convective Clouds and Chemistry (DC3) field experiment produced an exceptional dataset on thunderstorms, including their dynamical, physical, and electrical structures and their impact on the chemical composition of the troposphere. The field experiment gathered detailed information on the chemical composition of the inflow and outflow regions of midlatitude thunderstorms in northeast Colorado, west Texas to central Oklahoma, and northern Alabama. A unique aspect of the DC3 strategy was to locate and sample the convective outflow a day after active convection in order to measure the chemical transformations within the upper-tropospheric convective plume. These data are being analyzed to investigate transport and dynamics of the storms, scavenging of soluble trace gases and aerosols, production of nitrogen oxides by lightning, relationships between lightning flash rates and storm parameters, chemistry in the upper troposphere that is affected by the convection, and related source character...

Thunderstorms enhance tropospheric ozone by wrapping and shedding stratospheric air

A significant source of ozone in the troposphere is transport from the stratosphere. The stratospheric contribution has been estimated mainly using global models that attribute the transport process largely to the global scale Brewer-Dobson circulation and synoptic scale dynamics associated with upper tropospheric jet streams. We report observations from research aircraft that reveal additional transport of ozone-rich stratospheric air downward into the upper troposphere by a leading-line-trailing-stratiform (LLTS) mesoscale convective system (MCS) with convection overshooting the tropopause altitude. The fine-scale transport demonstrated by these observations poses a significant challenge to global models that currently do not resolve storm scale dynamics. Thus the upper tropospheric ozone budget simulated by global chemistry-climate models where large-scale dynamics and photochemical production from lightning-produced NO are the controlling factors may require modification.

Lightning-produced NOx (linox) : Experimental design and case study results

This paper investigates the role of lightning in the production of nitrogen oxides (NOx) and their subsequent distribution by thunderstorms. These questions were addressed by the field experiment LINOX (lightning produced NOx), which was performed in southern Germany in July 1996. The structure of thunderstorms was observed by radar and satellite, the lightning activity was recorded by a lightning detection network, and airborne chemical measurements were performed aboard a jet aircraft penetrating the storm anvils. NOx concentrations in the storm anvils were found to typically range from 1 to 4 parts per billion by volume. The NO contribution to the total NOx was found to be dominant in narrow peaks produced by flashes as well as near cloud boundaries, probably because of increased photolysis rates of NO2. Using CO2 as an air mass tracer, the lightning-produced NOx amount was discriminated from the contribution due to transport of air from the boundary layer. It was found from a case study of a large storm anvil that lightning-produced NOx was present in the same order of magnitude as the amount of NOx originating from lower levels; during later stages of cloud development, the content of the former even exceeded the latter one. A simple two-dimensional model of advection and dispersion of the lightning-produced NOx was able to reproduce the general structure of the anvil NOx plume. Some NOx peaks could directly be attributed to flash observations close to the aircraft track.

Airborne quantification of upper tropospheric NOx production from lightning in deep convective storms over the United States Great Plains

The reported range for global production of nitrogen oxides (NOx = NO + NO2) by lightning remains large (e.g., 32 to 664 mol NOx flash−1), despite incorporating results from over 30 individual laboratory, theoretical, and field studies since the 1970s. Airborne and ground-based observations from the Deep Convective Clouds and Chemistry experiment in May and June 2012 provide a new data set for calculating moles of NOx produced per lightning flash, P(NOx), in thunderstorms over the United States Great Plains. This analysis utilizes a combination of in situ observations of storm inflow and outflow from three instrumented aircraft, three-dimensional spatial information from ground-based radars and satellite observations, and spatial and temporal information for intracloud and cloud-to-ground lightning flashes from ground-based lightning mapping arrays. Evaluation of two analysis methods (e.g., a volume-based approach and a flux-based approach) for converting enhancements in lightning-produced NOx from volume-based mixing ratios to moles NOx flash−1 suggests that both methods equally approximate P(NOx) for storms with elongated anvils, while the volume-based approach better approximates P(NOx) for storms with circular-shaped anvils. Results from the more robust volume-based approach for three storms sampled over Oklahoma and Colorado during DC3 suggest a range of 142 to 291 (average of 194) moles NOx flash−1 (or 117–332 mol NOx flash−1 including uncertainties). Although not vastly different from the previously reported range for storms occurring in the Great Plains (e.g., 21–465 mol NOx flash−1), results from this analysis of DC3 storms offer more constrained upper and lower limits for P(NOx) in this geographical region.

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

Unique in situ measurements of CO, O3, SO2, CH4, NO, NOx, NOy, VOC, CN, and rBC were carried out with the German Deutsches Zentrum fur 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.

Injection of Lightning-Produced NOx, Water Vapor, Wildfire Emissions, and Stratospheric Air to the UT/LS as Observed from DC3 Measurements

During the Deep Convective Clouds and Chemistry (DC3) experiment in summer 2012, airborne measurements were performed in the anvil inflow/outflow of thunderstorms over the Central U.S. by three research aircraft. A general overview of Deutsches Zentrum fur Luft- und Raumfahrt (DLR)-Falcon in situ measurements (CO, O3, SO2, CH4, NO, NOx, and black carbon) is presented. In addition, a joint flight on 29 May 2012 in a convective line of isolated supercell storms over Oklahoma is described based on Falcon, National Science Foundation/National Center for Atmospheric Research Gulfstream-V (NSF/NCAR-GV), and NASA-DC8 trace species in situ and lidar measurements.

Thunderstorms: Trace Species Generators

In the upper troposphere, both natural and anthropogenic processes control the budget of nitric oxide (NO), a highly reactive and pollutant trace gas. The main local NO sources in the upper troposphere are emissions from aircraft and production by lightning. In the past 20 years, DLR studied the latter source in airborne field experiments accompanied with model simulations. The global lightning NO source is found to be distinctly larger than that from aircraft (factor ~5, uncertainty ~50–100 %). Lightning flashes in tropical regions seem to produce less NO per flash compared to other regions.

Long-Range Transport of Air Pollutants

Air pollutants may be transported over several 1 000 km ranges, across continents, oceans (intercontinental), hemispheres, or even globally, depending on lifetime and other properties. Transported emissions include primary pollutants emitted from industry and vehicles (e.g., nitric oxide) and natural pollutants released by forest fires (e.g., soot). Also secondary pollutants (e.g., ozone) that are formed near the source region undergo transport. Recent advances in understanding atmospheric transport pathways, source-receptor relationships, and transformation of pollutants during transport are described.

Lightning and NOX Production in Global Models

In the upper troposphere lightning is the major contributor to the production of nitric oxide, which is a critical precursor gas for ozone production. It is therefore important that this source is simulated with a high accuracy in global chemical transport models and global chemistry/climate models. This chapter reviews development of the parameterization of lightning-produced nitric oxide in such models and the various components required such as flash rate distribution, NO production per flash and its vertical distribution. The results from simulations with different global models, the uncertainties and the impact on ozone are discussed.