Seasonal forecasting of lightning and thunderstorm activity in tropical and temperate regions of the world.

Andrew J Dowdy

doi:10.1038/srep20874

Abstract

Thunderstorms are convective systems characterised by the occurrence of lightning. Lightning and thunderstorm activity has been increasingly studied in recent years in relation to the El Niño/Southern Oscillation (ENSO) and various other large-scale modes of atmospheric and oceanic variability. Large-scale modes of variability can sometimes be predictable several months in advance, suggesting potential for seasonal forecasting of lightning and thunderstorm activity in various regions throughout the world. To investigate this possibility, seasonal lightning activity in the world’s tropical and temperate regions is examined here in relation to numerous different large-scale modes of variability. Of the seven modes of variability examined, ENSO has the strongest relationship with lightning activity during each individual season, with relatively little relationship for the other modes of variability. A measure of ENSO variability (the NINO3.4 index) is significantly correlated to local lightning activity at 53% of locations for one or more seasons throughout the year. Variations in atmospheric parameters commonly associated with thunderstorm activity are found to provide a plausible physical explanation for the variations in lightning activity associated with ENSO. It is demonstrated that there is potential for accurately predicting lightning and thunderstorm activity several months in advance in various regions throughout the world.

Highlights

Thunderstorms can have a wide range of impacts on natural and built environments
Results are examined in relation to the potential for seasonal forecasting of lightning and thunderstorm activity, including through the use of hindcast NINO3.4 values obtained from the National Oceanic and Atmospheric Administration (NOAA)
There are some locations where Northern Annular Mode44 (NAM), North Atlantic Oscillation (NAO) and Quasi-Biennial Oscillation (QBO) are significantly correlated with lightning flash density, ranging from 3–8% of the study region, it is noted that these values are relatively small given that 5% of the study region on average could be expected to have a significant correlation at the 95% confidence level based on random chance

Summary

Introduction

Thunderstorms can have a wide range of impacts on natural and built environments. The lightning associated with thunderstorms can directly result in loss of life and damage to infrastructure[1,2,3,4], as well as lead to the occurrence of hazards such as wildfires[5,6,7,8]. The lightning data are examined in relation to seven different modes of variability: the El Niño/Southern Oscillation[43] (ENSO, as represented by the NINO3.4 index), an ocean-atmosphere coupled mode with strong interaction between the Walker Circulation and the Pacific Ocean; the Northern Annual Mode[44] (NAM, referred to as the Arctic Oscillation: AO) and the Southern Annular Mode[45] (SAM), both of which are characterised by north-south shifts in atmospheric mass between the polar regions and the middle latitudes; the North Atlantic Oscillation[46] (NAO), characterised by anomalous atmospheric pressure in the North Atlantic region; the Pacific-North American Pattern[46] (PNA), characterised by anomalous strength and location of the East Asian jet stream; the Indian Ocean Dipole[47] (IOD, as represented by the Dipole Mode Index, DMI), a coupled ocean-atmosphere phenomenon located in the tropical Indian Ocean; and the Quasi-Biennial Oscillation (QBO)[48], a quasi-periodic variation in stratospheric zonal winds in the tropics. Results are examined in relation to the potential for seasonal forecasting of lightning and thunderstorm activity, including through the use of hindcast (i.e. reforecast) NINO3.4 values obtained from the National Oceanic and Atmospheric Administration (NOAA)

Methods

Results

Conclusion