The convective storm system during IOP 2a of MAP: Cloud-to-ground lightning flash production in relation to dynamicsc and microphysics

Seity, Y. ; S. Soula ; P. Tabary ; G. Scialom

Année de publication
2003

This paper presents a study about correlation between cloud-to-ground <br>lightning flash (CG) activity, and the dynamics and microphysics of <br>thunderclouds. Data collected during Intense Observation Period (MAP <br>IOP) 2a of the Mesoscale Alpine Programme Special Observing Period (SOP)<br> over the Lago Maggiore Target Area (LMTA) in northern Italy are used. <br>IOP 2a was the most electrically active period during the SOP, <br>representing 75% of the total CG activity. Thunderclouds were strongly <br>vertically developed (the 30 dBZ echo tops were sometimes higher than 12<br> km) and produced large amounts of rainfall and some hail. Doppler and <br>polarimetric radar data allow us to retrieve the three-dimensional wind <br>and radar-reflectivity fields from two synchronous Doppler radars, and <br>particle-type fields in the thunderclouds from the S-Pol polarimetric <br>radar. Both polarities of CGs are distinguished. Temporal and spatial <br>relationships from the global activity over the LMTA are first studied. <br>Then, the temporal correlation between CG rates and dynamics or <br>microphysics for five individual cells is considered. A very strong <br>correlation is observed between CG and the presence of a mixture of <br>graupel and hail, which strongly supports a non-inductive charging <br>mechanism. CG impacts seem to be located underneath large <br>radar-reflectivity values and around the maximum vertical velocities. <br>Two individual cells are studied in more detail, in order to better <br>understand their different electrical behaviours: the first produced <br>mainly negative CGs, and the second produced 61% positive CGs in the <br>second phase of its lifetime. The association of positive CGs with <br>severe weather and especially with the presence of hail is observed. <br>Copyright © 2003 Royal Meteorological Society.</div>

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