- Director's Message
- Table of Contents
- Strategic Goals: Science, Facilities & Technology
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Strategic Goal #1, Strategic Priority #1:
Exploring atmospheric, Earth System, and solar processes, variability, and change -
Strategic Goal #1, Strategic Priority #2:
Investigating the interaction of the atmosphere, the broader Earth system, and human society -
Strategic Goal #1, Strategic Priority #3:
Improving prediction of weather, climate, and other atmospheric phenomena -
Strategic Goal #1, Strategic Priority #4:
Developing community models -
Strategic Goal #5, Strategic Priority #1:
Enabling innovative field experiments and measurement campaigns -
Strategic Goal #5, Strategic Priority #2:
Developing new instrumentation
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Strategic Goal #1, Strategic Priority #1:
- Research Catalog
Christelle Barthe
Postdoctoral Fellow
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Project Summary:
Click on picture to view the entire figure
Figure 1. Observed (thick line) and simulated (thin line) total lightning flash rate (min-1) for the 10 July 1996 STERAO storm (top) and the 12 July 1996 STERAO storm (bottom). The right figures correspond to the mean total flash rate per 10 min interval whereas the left figures represent the total flash rate per 1 min interval. The simulated total flash rate is calculated from the non-precipitation and the precipitation ice mass fluxes product. Convection is a key-process for the redistribution of chemical species from the boundary layer to the free troposphere and also for the cleansing of the atmosphere through scavenging. In deep convection events, production of nitrogen oxides (NOx) by lightning flashes is a major way to distribute NOx directly in the mid- and upper troposphere. Nitrogen oxides are important trace gases in the atmosphere since they are a precursor of the tropospheric ozone which is an important greenhouse gas. They also control the photochemical regimes of the troposphere and the hydroxyl radical concentration which is the main oxidant of numerous chemical species. The climatic impact of lightning-produced NOx (LNOx) is all the more important as they are produced in the upper troposphere where their lifetime is increased compared to the lower troposphere. However, a large uncertainty exists in LNOx production at the global scale with estimates ranging from 2 to 20 Tg(N) yr-1. So, in order to reduce the uncertainties of LNOx in global models, it is necessary to better know the processes involved in NO production by lightning flashes, and to display key-processes and important parameters with simulations at the cloud scale. A new lightning-produced NOx parameterization for cloud-resolving model has been developed. This parameterization consists of three parts: flash rate, spatial distribution of the lightning channel and NO production rate. First, the flash rate can be given by observations or deduced from model parameters. The flux hypothesis has been evaluated with the WRF model on different convective cases (the 10 and 12 July 1996 STERAO storms, and the 13 July 2005 Huntsville, AL, storm) in collaboration with Wiebke Deierling (EOL) and Mary Barth (ACD). This hypothesis correlates the precipitation and non-precipitation ice mass flux product with the total lightning flash rate in a thunderstorm, suggesting that some microphysics parameters can be used as a proxy of lightning in modeling studies (Figure 1). Several sensitivity tests have also been performed to investigate the sensitivity of this parameterization to the microphysics and to the horizontal resolution of the model domain (Barthe et al., manuscript in preparation). Secondly, the spatial distribution of the lightning channel is no more volumetric as in previous parameterizations, but attempts to reproduce the global morphology of a lightning flash. The NO molecules are then produced along a virtual lightning flash path in function of the pressure. This parameterization is tested on the 10 July 1996 STERAO storm and sensitivity tests are performed. In particular, the relative impact of short duration flashes, cloud-to-ground flashes and flash length distribution is investigated. First results suggest that previous parameterizations tended to overestimate the NO production rate per flash due to the assumption that NO molecules are instantly diluted over a large region of the cloud (Barthe and Barth, manuscript in preparation). The use of the non-precipitation and precipitation ice mass flux product as a proxy for the total lightning flash rate needs further investigation. In particular, several convective cases will be simulated to investigate if this relationship is invariant over land and ocean, and over mid-latitude and tropics. The LNOx parameterization will also be tested in different environment (STERAO, TROCCINOX, AMMA). A new way for parameterizing the total flash rate from ice microphysics at the global scale should also be investigated with the CAM model. |
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Publications: |
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Barth, M. C., S.-W. Kim, C. Wang, K. E. Pickering, L. E. Ott, G. Stenchikov, M. Leriche, S. Cautenet, J.-P. Pinty, C. Barthe, C. Mari, J. H. Helsdon, R. D. Farley, A. M. Fridlind, A. S. Ackerman, V. Spiridonov, B. Telenta, 2007: Cloud-scale model intercomparison of chemical constituent transport in deep convection. Atmos. Chem. Phys., 7, 4709-4731 Barth, M. C., S.-W. Kim, C. Wang, K. E. Pickering, L. E. Ott, G. Stenchikov, M. Leriche, S. Cautenet, J.-P. Pinty, C. Barthe, C. Mari, J. H. Helsdon, R. D. Farley, A. M. Fridlind, A. S. Ackerman, V. Spiridonov, B. Tosko, 2007: Cloud-scale model intercomparison of chemical constituent transport in deep convection. Atmos. Chem. Phys. Discuss., 7, 8035-8085 Barthe, C., J. P. Pinty, 2007: Simulation of a supercellular storm using a three-dimensional mesoscale model with an explicit flash scheme. J. Geophys. Res., 112, D06210, doi: 10.1029/2006JD007484 Barthe, C., J. P. Pinty, C. Mari, 2007: Lightning-produced Nox in an explicit electrical scheme tested in a stratosphere-troposphere experiment: Radiation, aerosols, and ozone case study. J. Geophys. Res., 112, D04302, doi: 10.1029/2006JD007402 |
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