Climatological Aspects of RHESSI Observed Terrestrial Gamma-Ray Flash Events

Association of terrestrial gamma-ray flashes (TGFs) with thunderstorm systems has been demonstrated in recent studies. Seasonal frequencies of TGF events observed with the RHESSI spacecraft over the past 4 years show patterns that are highly correlated with regional zones of convergence, such as the intertropical convergence zone (ITCZ). The TGF geographic distributions are also found to be in regions with deeply penetrative convection. Additional meteorological background for TGF events are developed from atmospheric analyses (the NCEP/NCAR Reanalysis) in a TGF relative framework. Particular focus is placed on Africa, with over 150 events, where distinctive seasonal patterns are noted in both the atmospheric setting and TGF frequency. The climatological setting is examined for atmospheric parameters that may be prerequisites for TGF events.