A lightning climatology of the South-West Indian OceanNatural Hazards and Earth System Science, 12, 2659-2670, 2012Author(s): C. Bovalo, C. Barthe, and N. BègueThe World Wide Lightning Location Network (WWLLN) data have been used to
perform a lightning climatology in the South-West Indian Ocean (SWIO) region
from 2005 to 2011. Maxima of lightning activity were found in the Maritime
Continent and southwest of Sri Lanka (>50 fl km−2 yr−1)
but also over Madagascar and above the Great Lakes of East Africa
(>10–20 fl km−2 yr−1). Lightning flashes within tropical
storms and tropical cyclones represent 50 % to 100 % of the total
lightning activity in some oceanic areas of the SWIO (between 10° S
and 20° S).
The SWIO is characterized by a wet season (November to April) and a dry
season (May to October). As one could expect, lightning activity is more
intense during the wet season as the Inter Tropical Convergence Zone (ITCZ) is present over all the basin.
Flash density is higher over land in November–December–January with values
reaching 3–4 fl km−2 yr−1 over Madagascar. During the dry
season, lightning activity is quite rare between 10° S and
25° S. The Mascarene anticyclone has more influence on the SWIO
resulting in shallower convection. Lightning activity is concentrated over
ocean, east of South Africa and Madagascar.
A statistical analysis has shown that El Niño–Southern Oscillation mainly
modulates the lightning activity up to 56.8% in the SWIO. The Indian Ocean
Dipole has a significant contribution since ~49% of the variability
is explained by this forcing in some regions. The Madden–Julian Oscillation
did not show significative impact on the lightning activity in our study.