Task 114

Using a Cloud-resolving Model to Simulate Lightning NOx Production During the TC4 Experiment

Principal Investigator(s):

K. Cummins

Sponsor(s):

K. Pickering

Last Updated:

October 26, 2012 15:25:24

Description of Problem

Lightning NOx production is the largest uncertainty related to the overall global NOx budget. Cloud-resolved chemistry simulations for observed thunderstorms can be used to make estimates of average NOx production per flash. Lightning and airborne chemistry observations are available from the Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere (SCOUT-O3) and Aerosol and Chemical Transport in Tropical Convection (ACTIVE) field campaign. Therefore, it is useful to simulate a convective event from SCOUT-O3/ACTIVE, in particular a tropical thunderstorm over the Tiwi Islands located north of Darwin, Australia, on 16 November 2005. NOx production from lightning throughout the storm duration can lead to the formation of ozone downwind of the storm anvil following storm dissipation.

Ozone production downwind of thunderstorms has a large impact on the upper tropospheric ozone budget. We will be testing the hypothesis from the literature that on average a tropical flash may make less NOx than a midlatitude flash and the application of a new lightning flash rate parameterization scheme in the Hector storm simulation.

Scientific Objectives and Approach

Our specific tasks are:

• Prepare a detailed description and set of background information on lightning-generated NOx in cloud-resolving models and flash rate parameterization schemes

• Prepare overviews of the SCOUT-O3/ACTIVE experiment and the associated aircraft flights, the 16 November 2005 convective event over the Tiwi Islands, the C-Band Polarimetric radar data, Lightning Location Network (LINET), and radiosonde data

• Use the Tropospheric Ultra-Violet (TUV) program to obtain nitrogen dioxide photolysis rates for the estimation of nitric oxide through the photostationary state approximation

• Learn to run the Weather and Research Forecasting Aqueous Chemistry (WRF-AqChem) model and prepare the initial condition input data

• Plan and conduct WRF-AqChem model simulations: (1) Meteorology-only, (2) Meteorology and Chemistry, and (3) Meteorology, Chemistry, and Lightning production

• Analyze WRF model results (plots of the vertical distribution of NOx and other chemistry species, storm evolution), and compare observations and simulations of the convective event

• Compare simulated lightning-NOx values from the Hector storm with the annual global production rate and estimates from midlatitude, subtropical, and other Hector storms

Accomplishments

We successfully incorporated meteorological and chemistry observations into the cloud-resolving/chemistry model to reproduce the single-cell Hector storm and its chemical composition. Meteorological simulations produced the storm roughly two hours earlier than observed, but successfully represented the observations in terms of storm evolution and intensity. Figure 1 shows the simulated evolution of NOx within this storm.

We concluded that nearly 500 moles of NO per flash were produced on average in this storm. This estimate provided lightning-NOx values that were similar to those observed by the Egrett aircraft (Figure 2). This production value was also similar to the lightning-NOx production rates suggested for midlatitude (DeCaria et al., 2000, 2005) and subtropical storms by Ott et al. (2010) and slightly greater than those determined by Huntreiser et al. (2009) using aircraft measurements for the 19 November 2005 Hector storm.

Other Publications and Conferences

Cummings, K. A., K. E. Pickering, M. C. Barth, T. Huntemann, W. C. Skamarock, G. Vaughan, A. Volz-Thomas, H. Schlager, and H. Holler, 2010. Application of a New Lightning-NOx Parameterization in a Hector Thunderstorm Cloud/Chemistry Simluation. 5th Conference on the Meteorological Applications of Lightning Data, January, Seattle, WA.

Task Figures

Fig. 1 –

Fig. 2 –