Abstract. Lightning-produced nitrogen oxides (LNOx=LNO+LNO2) are an important source of upper tropospheric ozone. Typical parameterizations of LNOx in chemistry-climate models introduce a constant amount of NOx per flash or per flash type. However, recent satellite-based NO2 measurements suggest that the production of LNOx per flash depends on the lightning flash frequency. In this study, we implement a new parameterization of LNOx production per flash based on the lightning flash frequency into a chemistry-climate model to investigate the implications for the chemical composition of the atmosphere. We find that a larger injection of LNOx in weak thunderstorms leads to a larger mixing ratio of NOx in the lower and the middle troposphere, and to a lower mixing ratio of NOx in the upper troposphere. The mixing ratios of O3, CO, HOx, HNO3 and HNO4 in the troposphere are influenced by the simulated changes of LNOx. Our findings indicate a larger release of nitrogen oxides from lightning in the lower and the middle atmosphere, producing a slightly better agreement with the measurements of tropospheric ozone at a global scale. In turn, we obtain a small decrease of the lifetime of methane and of carbon monoxide.
Abstract. Lightning is an important natural source of nitrogen oxide especially in the middle and upper troposphere. Hence, it is essential to represent lightning in chemistry transport and coupled chemistry-climate models. Using ERA-Interim meteorological reanalysis data we compare the lightning flash density distributions produced using several existing lightning parametrisations, as well as a new parametrisation developed on the basis of upward cloud ice flux at 440 hPa. The use of ice flux forms a link to the non-inductive charging mechanism of thunderstorms. Spatial and temporal distributions of lightning flash density are compared to tropical and subtropical observations for 2007–2011 from the Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measuring Mission satellite. The well-used lightning flash parametrisation based on cloud-top height has large biases but the derived annual total flash density has a better spatial correlation with the LIS observations than other existing parametrisations. A comparison of flash density simulated by the different schemes shows that the cloud-top height parametrisation has many more instances of moderate flash densities and fewer low and high extremes compared to the other parametrisations. Other studies in the literature have shown that this feature of the cloud-top height parametrisation is in contrast to lightning observations over certain regions. Our new ice flux parametrisation shows a clear improvement over all the existing parametrisations with lower root mean square errors and better spatial correlations with the observations for distributions of annual total, and seasonal and interannual variations. The greatest improvement with the new parametrisation is a more realistic representation of the zonal distribution with a better balance between tropical and subtropical lightning flash estimates. The new parametrisation is appropriate for testing in chemistry transport and chemistry-climate models that use a lightning parametrisation.
Abstract. An air pollution plume from Southern and Eastern Asia, including regions in India and China, was predicted by the FLEXPART particle dispersion model to arrive in the upper troposphere over Europe on 24–25 March 2006. According to the model, the plume was exported from Southeast Asia only six days earlier, transported into the upper troposphere by a warm conveyor belt, and travelled to Europe in a fast zonal flow. This is confirmed by the retrievals of carbon monoxide (CO) from AIRS satellite measurements, which are in excellent agreement with the model results over the entire transport history. The research aircraft DLR Falcon was sent into this plume west of Spain on 24 March and over Southern Europe on 25 March. On both days, the pollution plume was indeed found close to the predicted locations and, thus, the measurements taken allowed the first detailed characterization of the aerosol content and chemical composition of an anthropogenic pollution plume after a nearly hemispheric transport event. The mixing ratios of CO, reactive nitrogen (NOy) and ozone (O3) measured in the Asian plume were all clearly elevated over a background that was itself likely elevated by Asian emissions: CO by 17–34 ppbv on average (maximum 60 ppbv) and O3 by 2–9 ppbv (maximum 22 ppbv). Positive correlations existed between these species, and a ΔO3/ΔCO slope of 0.25 shows that ozone was formed in this plume, albeit with moderate efficiency. Nucleation mode and Aitken particles were suppressed in the Asian plume, whereas accumulation mode aerosols were strongly elevated and correlated with CO. The suppression of the nucleation mode was likely due to the large pre-existing aerosol surface due to the transported larger particles. Super-micron particles, likely desert dust, were found in part of the Asian pollution plume and also in surrounding cleaner air. The aerosol light absorption coefficient was enhanced in the plume (average values for individual plume encounters 0.25–0.70 Mm−1), as was the fraction of non-volatile Aitken particles. This indicates that black carbon (BC) was an important aerosol component. During the flight on 25 March, which took place on the backside of a trough located over Europe, a mixture of Asian pollution and stratospheric air was found. Asian pollution was mixing into the lower stratosphere, and stratospheric air was mixing into the pollution plume in the troposphere. Turbulence was encountered by the aircraft in the mixing regions, where the thermal stability was low and Richardson numbers were below 0.2. The result of the mixing can clearly be seen in the trace gas data, which are following mixing lines in correlation plots. This mixing with stratospheric air is likely very typical of Asian air pollution, which is often lifted to the upper troposphere and, thus, transported in the vicinity of stratospheric air.
The structures of severe mesoscale precipitation systems (MPS) in Switzerland have been classified by analyzing radar images obtained over a 5-yr period. Severe MPSs were defined to be those producing most of the damage on days on which at least 5 (out of 2400) communities reported water and/or at least 20 reported hail damage. Of 94 MPSs selected, 82 had radar reflectivity of 47 dBZ or greater and were referred to as mesoscale convective systems (MCS). The 12 remaining MPSs consisted of less intense, long-lasting, and widespread frontal or orographic rainfall. Subclasses of MCSs were defined according to their internal arrangements of cell complexes (CC). A CC was defined as an echo contour of 40 dBZ surrounding echo maxima of at least 47 dBZ. Four general categories of organization were found: isolated CC, a group of CCs, and a broken or continuous line of CCs. All categories can be purely convective at the mature stage, or the CCs may be juxtaposed with a stratiform precipitation area, usually behind moving convection. The stratiform region often developed as a decaying convective area. These categories were examined in relation to sounding, surface mesonet, synoptic weather type, and severe weather information. In 26 cases, the MCS had “leading line-trailing stratiform” structure. These MCSs were graded according to a classification scheme previously used to characterize spring rainstorms in Oklahoma. Only moderately and weakly classifiable storm systems occurred in Switzerland. The mountain barriers apparently interfered with the airflow such that MCSs were prevented from having enough time and space to develop to a higher degree of organization as is possible over the relatively flat terrain of Oklahoma. In addition, the instability and the wind shear in the Swiss storm environment was found to be weaker.
Wetlands in the high northern latitudes are a major, yet poorly known contributor to the global methane (CH4) budget. In wetlands, peat bogs and lakes, CH4 is produced by organic degradation processes. These natural emissions are affected by climate change though, e.g. by changing temperatures and permafrost thaw. A better understanding is essential also for discussing the human role in the budget of this important greenhouse gas and mitigation options.However, the data coverage in the region is still thin: accessibility is limited, satellite sensors struggle with the high solar zenith angle, difficult surface and thermodynamic conditions, or clouds. Corresponding emission inventories and models differ significantly, in the distribution as well as in the amount of emissions. Based in Kiruna/Sweden, the French MAGIC initiative addressed these knowledge gaps by bringing together a multitude of instruments on three research aircraft (Safire ATR-42, BAS Twin Otter, DLR Cessna) and various other platforms for measurements in northern Scandinavia in August 2021.Here we focus on airborne in-situ measurements with the DLR Cessna. The suite of instruments aboard the aircraft included a meteorological sensor package, a Picarro, and an Aerodyne QCLS, providing CH4,CO2, C2H6, 13C(CH4), temperature, H2O, 3d-wind, all along the flight track.The Cessna conducted 12 scientific flights in the region, which mostly targeted and scouted hotspots of CH4 emissions indicated by wetland emission inventories. The flights were coordinated as often as possible with other airborne, ground-based and satellite platforms to allow for intercomparisons and for providing ground truth for remote sensing instruments. Estimating CH4 emission fluxes is another major objective, which is challenging because of spatial and temporal heterogeneity of these area sources. To this end we tried a combination of different methods and flight patterns. We provide an overview of the measurements, discuss the different flight strategies and show first results of the analyses that are ongoing in the frame of the ESA MAGIC4AMPAC project.
Abstract 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 für Luft‐ und Raumfahrt (DLR)‐Falcon in situ measurements (CO, O 3 , SO 2 , CH 4 , NO, NO x , 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. During DC3 some of the largest and most destructive wildfires in New Mexico and Colorado state's history were burning, which strongly influenced air quality in the DC3 thunderstorm inflow and outflow region. Lofted biomass burning (BB) plumes were frequently observed in the mid‐ and upper troposphere (UT) in the vicinity of deep convection. The impact of lightning‐produced NO x (LNO x ) and BB emissions was analyzed on the basis of mean vertical profiles and tracer‐tracer correlations (CO‐NO x and O 3 ‐NO). On a regular basis DC3 thunderstorms penetrated the tropopause and injected large amounts of LNO x into the lower stratosphere (LS). Inside convection, low O 3 air (~80 nmol mol −1 ) from the lower troposphere was rapidly transported to the UT/LS region. Simultaneously, O 3 ‐rich stratospheric air masses (~100–200 nmol mol −1 ) were present around and below the thunderstorm outflow and enhanced UT‐O 3 mixing ratios significantly. A 10 year global climatology of H 2 O data from the Aura Microwave Limb Sounder confirmed that the Central U.S. is a preferred region for convective injection into the LS.
Airborne trace gas measurements carried out over southern Brazil during TROCCINOX-1 with the Falcon aircraft are compared to results from three global models: ECHAM, MATCH and TM4. The agreement between the models, with different parameterizations for lightning-produced NOX (=NO+NO2), and the measurements is investigated along single flight tracks. A new parameterization based on the mass flux in the updrafts [Grewe et al., 2001; Kurz and Grewe, 2002] shows promising results in comparison to the more commonly used parameterization based on the cloud top height [Price and Rind, 1992]. The most realistic model results for the total amount of lightning-produced NOX on the global scale were achieved with 5 Tg(N) yr-1.
