85th AMS Annual Meeting

Tuesday, 11 January 2005: 2:45 PM
Application of ground-based lightning flash network data in flight planning for the NASA Intercontinental Chemical Transport Experiment North America (INTEX-NA)
K. Pickering, University of Maryland, College Park, MD; and A. M. Thompson, T. Kucsera, L. Pfister, H. B. Selkirk, M. A. Avery, E. V. Browell, and R. Cohen
Lightning flashes produce nitric oxide (NO) in quantities that remain relatively uncertain. However, it is well known that lightning can produce sufficient NO to strongly influence ozone photochemistry, especially in upper tropospheric outflow regions downwind of thunderstorms. The NASA INTEX-NA experiment was designed to characterize the export of tropospheric trace gases and aerosols from North America to the North Atlantic through a series of flights of the NASA DC-8 aircraft in Summer 2004. Considerable planning went into each flight to maximize the scientific return. A flight planning forecast product that we produced prior to each flight was a set of maps of the accumulated influence of lightning on air parcels in the middle and upper troposphere over the previous 5 days. We construct this product in the following manner. National Lightning Detection Network flash counts on a 1 x 1 deg. grid are determined for each hour of the day. Five-day back trajectories are initialized at each point on the grid at specific middle and upper tropospheric levels, and lightning flash counts are accumulated along the trajectory paths and the resulting sums are assigned to the grid boxes corresponding to where the trajectories are initialized. A color-coded map is then constructed based on the entire array of these grid values. Accumulation of flashes along trajectories is valid because NOx has a 5-10 day lifetime in the upper troposphere. We compare our forecast product with chemical data collected on DC-8 flights with considerable convection/lightning influence. Enhancement of NO and NO2 mixing ratios will be examined in regions downwind of convection. We will also compare the locations of enhanced NOx oxidation products (PANs and nitric acid) with the locations of aged lightning-influenced air parcels. Upper tropospheric ozone enhancements were noted in the in-situ measurements as well as in vertical profiles observed by lidar in regions predicted to have air parcels with large amounts of aged lightning influence.

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