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A correlated high-speed image and E-field observation of natural lightning attachment process on a time scale of sub-microsecond has been performed. In one of the observed events, downward stepped leader pulses can be clearly identified either in E-filed or optical signals. When the stepped leader approaches within about three hundred meters of ground, optical pulses begin to appear in the lowest 40 m channel section. These pulses have larger amplitude than the pulses from the downward stepped leader. It appears that these pulses are produced by an upward connecting leader. These facts suggest that the upward connecting leader is also stepped and it could produce even stronger pulses than the corresponding downward leader. The downward stepped leader has a velocity of about 4x106 m/s, while the upward leader has the velocity of about 1.7x106 m/s. The return stroke pulses observed in the E-field and in the optical signal agree well in time but differ in fine structures.

Some special features of cloud-to-ground (CG) lightning discharges in the verge of Qinghai-Tibetan Plateau have been found by using the data from wide-band slow antenna system with 1μs time resolution. It has been found that (CG) lightning usually follows intracloud (IC) discharges. K-changes during the IC discharge part initiate from negative charge region and propagate downward to the lower positive charge region with an average speed of 1.5×107 m/s. The radiation waveforms of return stoke begin with a slow front which last for about 9.4 μs to about half of the field peak amplitude, and the zero-to-peak rise time was 10.9μs for negative first return strokes.