Radar Observations of the Effects of Changing Electric Fields on the Orientations of Hydrometeors
PHILLIPS LAB HANSCOM AFB MA
Pagination or Media Count:
The changing orientations of hydrometeors due to rapidly changing electric fields in clouds have been observed for the first time at a radar wavelength of 11 cm S-band with the polarimetric Doppler radar operated in Sudbury, MA by the Geophysics Directorate of Phillips Laboratory. During 1991 the radar was operated in a half-matrix mode, transmitting a signal of right circular polarization and receiving signals of right and left circular polarization. Observations of electrified storms on nine days during the spring and summer of 1991 revealed several occurrences of lightning that coincided with significant changes of the circular depolarization ratio CDR, the cross- correlation, or the phase of the cross-covariance of the two received signals. Changes up to 2 dB in CDR, 50 in cross-correlation, and 40 deg in phase were observed. However, many occurrences of lightning observed by radar were not accompanied by detectable changes of hydrometeor orientations, and there were no observations of the cyclical changes of the polarimetric quantities that have been observed elsewhere with radars of shorter wavelength. Examples of observations are presented and implications for future measurements with this radar are discussed.
- Atmospheric Physics
- Active and Passive Radar Detection and Equipment