Characteristic Of Temperatures On Lightning Return Stroke

By using slit-less spectrograph and OMA, observations on spectra of natural lightning have been carried out in Qinghai plateau and in the coastal area of Guangdong. Slit-less spectra for first return strokes of lightning between the cloud and ground have been obtained. Spectrum analysis and line identification have been done. A NI emission line at 444.2nm was first observed on the lightning spectrum of return stroke19:21:41.According to the relative intensities of lines and transition parameters obtained by Multi-configuration Dirac-Fock (MCDF) method, temperatures in lightning discharge channel have been calculated by using multiple-line method, also by using double-line method. To compare these data obtained by the two methods, it is found that using multiple-line method could minimize error resulting from choosing different lines in double-line method. So the result shows that multiple-line method is better than double-line method to studying temperature in lightning return stroke channel.After spectrum analysis and line identification have been done, temperatures for individual lightning strokes and at different heights of the discharge channel have been calculated by using multiple-line method. The result shows that the temperatures in return stroke channel vary from stroke to stroke. In general, the more intensive lightning discharge, the higher is the value of channel temperature. On the other hand, for a certain return stroke channel, temperatures at different positions show signs of falling away with increasing height alone the discharge channel. Compared with that of Qinghai plateau, channel temperatures in Guangdong coastal area are higher, and lightning is more intensive, and lines from the higher excitation potential of NII in these lightning spectra are easier observed.