Calibration And Application Of Data Measured By Electric Field Mills

Based on a brief introduction of atmospheric electric field (AEF), especially lightning electric field, this paper made a probe into calibration and application of data measured by electric field mills, which is kind of reference to qualitative control and of importance to lightning surveillance and prediction.Because the AEF-mills are rather sensitive, discrepancy is caused by different mounting styles and site surroundings though lab calibrations are carried out before installment. Inaccuracy, inconformity and incomparability will exert a negative impact on usage and study of their data afterwards in the network observation. Such conclusions are found about calibration of the AEF-mills on the basis of situ-experiments and simulation:(1) Orientation of the probes makes no systematic difference to the results, while downward probes could minimize effects of charged raindrops in the perennial and all-weather observation. (2) EF distortion is caused by the columns of the mills. Such equations could be used to calibrate y1 measured by raised probes to y2 on the ground,|y1|<5kV/m, y2=0.26y1;|y1|≥5kV/m, y2=0.63y1. (3) AEF-mills mounted on the roof of the buildings will get increased results. More increased data is observed by mills on taller buildings. (4) AEF-mills mounted near waters will get decreased results especially in fine days. More decreased data is observed by mills nearer to waters. Elevation difference of Several dozens of meters makes no considerable difference to the results.We preliminarily analyzed AEF geographical distribution and daily fluctuation in fine weather in Jiangsu and found its distribution had a correspondence with content of aerosols in the air and that there were two characteristics of its daily variation. The one was double valleys & double peaks, and the other was single valley & single peak. Such traits as follows are shown before thunderstorms:(1)ascent, descent or oscillating wave patterns;(2)increasing amplitudes; (3) increasing variation rate; (4) polarity reversion, which could be used in lighting prediction: from the time when lighting positioning system detects the first strike in 25km around the AEF-mill site on, if there are ascent, descent or oscillating wave patterns and the AEF amplitude is 15.6 times as much as that in fine weather in presence of increasing variation rate and polarity reversion, lighting alerts could be on in 15.6 minutes, strikes in this region are due in 19.1 minutes.