Saharan dust, lightning and tropical cyclones in the eastern tropical Atlantic during NAMMA‐06

Abstract

During the summer of 2006, the downstream component of African Monsoon Multidisciplinary Analyses Campaign (NASA‐AMMA (NAMMA)) examined African Easterly Waves (AEWs) emerging from the coast of Africa. Six of these disturbances went on to become named systems in the Tropical Atlantic. Two of the six systems (Tropical storm Debby and Hurricane Helene) developed in the extreme eastern Atlantic and were associated with dust outbreaks, elevated ice contents and frequent lightning. Here we show that in the early tropical cyclo‐genesis stages of these systems there were thousands of cloud‐to‐ground (CG) lightning flashes as measured by a ground‐lightning network. TRMM overpasses show high precipitation ice content above the freezing level and high latent heat release. Super‐cooled water can be inferred in the lower parts of cloud systems in concert with observed high ice concentrations at high altitudes creating charge separation based on the large numbers of CG flashes.