Land cover, lightning frequency, and turbulent fluxes over Southern Louisiana

Abstract

Lightning is one of the most impactful weather phenomena but little precise and accurate information is known about how its frequency is impacted by changes in land use/land cover (LULC). Similarly, little is known about the spatial and temporal variability of the convective (i.e., turbulent) fluxes of sensible and latent heat that fuel the updrafts associated with lightning under changing LULC. This research applies NOAA's gridded annual lightning data from the National Lightning Detection Network (NLDN), gridded annual mean convective flux data from the North American Regional Reanalysis database (NARR), and LULC classification data from the NOAA Coastal Change Analysis Program (C-CAP) to analyze frequency changes in lightning and the turbulent fluxes across a swath of Louisiana, U.S.A., over the years 1996–2011. Results suggest that urban areas have the highest means of CG lightning with a consistent mean of approximately 152 flashes per km−2. However, urban areas support less convective flux of sensible (latent) heat than five (four) of six other generalized land classes tested. Lightning frequency tends to be positively related to latent heat fluctuations but less directly related to sensible heat, at least at the annual time scale, as we see positive relationships in all land classes except unconsolidated shore (p < 0.05). Collectively, these results suggest that land use change should be considered carefully in models of future projections of severe weather events and climate.