COULD CLOUD-TO-CLOUD DISCHARGES BE AS EFFECTIVE AS CLOUD-TO-GROUND DISCHARGES IN PRODUCING NOX

In global models of tropospheric ozone and oxidized nitrogen, it is us ually assumed that cloud-to-cloud discharges are 3 to 10 x less effect ive than cloud-to-ground discharges in producing nitrogen oxides (NOx) . This assumption is based on a limited number of observations and exp eriments regarding the acoustic and optical energy spectrum of lightni ng discharges. We claim that cloud-to-cloud and cloud-to-ground discha rges dissipate similar amounts of energy and they may thereby be equal ly effective per discharge as NOx producers. Nevertheless, the mechani sm of NOx production by electrical discharges still needs to be clarif ied, as well as whether there is a vertical differentiation in the pro duction mechanism. We performed sensitivity studies with a global 3-D climatological tracer model (MOGUNTIA). The studies indicate that the simulated tropospheric distributions of oxidized nitrogen and ozone ar e sensitive to the vertical distribution of the lightning source assum ed. Furthermore, it is shown that the strength of the global lightning source used in 3-D global model studies of oxidized nitrogen should b e amplified by a factor of 2.6 if cloud-to-cloud discharges are equall y effective as cloud-to-ground discharges in producing nitrogen oxides .