Thunderstorm trends over Africa

Thunderstorms inflict death and damage worldwide due to lightning, heavy rains, hail, and strong winds. While the effect of global warming on future thunderstorm activity is still debatable, this work investigates how thunderstorm activity over Africa may have changed over the last 70 years. Thunderstorm data were obtained from the World Wide Lightning Location Network (WWLLN) and processed to produce thunderstorm clusters. The number and area of clusters in one year (2013) were compared with several climate parameters tied to thunderstorm development, taken from the NCEP-NCAR Reanalysis-1 product (NCEP). The two parameters that correlated best with thunderstorm number were lifted index and specific humidity, with correlations of 20.795 and 0.779, respectively. These parameters were used to construct an empirical model that predicts the number and area of thunderstorm clusters over Africa on a particular day, month, or year. The empirical model was run from 1948 to 2016, providing a reconstruction of long-term thunderstorm activity over Africa. The time series was compared to temperature data from NCEP, and showed that the number of clusters increased with rising surface temperature on annual and decadal time scales, particularly since the mid-1990s. On an annual time scale, the number and area of thunderstorm clusters exhibited a highly sensitive relationship with surface temperature, with a;40% increase in the number of thunderstorm clusters for every 1-K rise in temperature over Africa. The correlation coefficients with surface temperature were 0.745 and 0.743 for cluster number and area, respectively, indicating that surface temperature explains;55% of the variability in interannual thunderstorm clusters over the past 70 years.