A 3-year study of cloud-to-ground lightning flash characteristics of Mesoscale convective systems over the Western Mediterranean Sea

Abstract

In this paper cloud-to-ground (CG) lightning flashes of 33 Mesoscale Convective Systems (MCSs) over the Western Mediterranean area are analyzed. Mean values of 22% for the positive CG ratio, 1.1 (2.4) for positive (negative) CG multiplicity, 17 kA (22.6 kA) of peak current for the positive (negative) CG flashes and a mean flash rate of around 13 min(-1) are obtained. The percentage of positive CGs and the multiplicity of negative CG are higher, while the mean peak currents are lower than in previous studies on MCSs. A more detailed case analysis reveals that there are great differences among the CG characteristics of MCSs. The life cycle of CG lightning associated with MCSs is also analyzed. The growing stages of MCSs are characterised by high CG lightning activity. The positive CG flash rate generally reaches a maximum before the negative CG flash rate does. In both cases the peak is recorded before or when MCSs show the largest area. Maximum flash rate and densities coincide with the area where the MCS shows the minimum cloud-top temperatures and therefore shows highest vertical development.