Meteorological cycles

Abstract

Abstract Atmospherics are electromagnetic wave‐pulses with a maximum of energy near 10 kHz, adequate to a wavelength of 30 km (Kimpara, 1963). Sources of atmospherics are mainly lightning flashes. Ten years of registration of atmospherics at Berlin‐Dahlem 1960 to 1970, permitted us to discover both annual and daily cycles in atmospherics. EQUIPMENT: The atmospherics were measured undirected by a VLF‐broadband‐receiver of a medium frequency at 10 kHz (‐3 dB: 3 to 40 kHz). The pulses were registered at two amplitude‐thresholds: A1 > 0.02 V/m and A2 > 0.4 V/m. The results of registrations show an exponential amplitude distribution with relatively high (low) puls‐rate at low (high) amplitudes of atmospherics. 10‐year ‐means: A1‐stage: 2.2 Hz; A2‐stage: 3.4.10‐2 Hz. ANNUAL CYCLES: The annual cycles in atmospherics in general follow sun's altitude, partly with phase shift. Maximum of pulse‐rate was reached at June (10‐years monthly means: fA1 =4.7 Hz; fA2 =8.8.10‐2 Hz), minimum at February/March (fA1=0.65Hz; fA2 =0.88.10‐2Hz). The mean max./min.‐ratio of pulse‐rates characterizing mean annual variations amounts to 7.2 (A1 ‐stage) and 10 (A2‐stage). DAILY CYCLES: In the winter‐time daily cycles in atmospherics show maximum‐values of pulserate at night and minimum‐values at day, caused by different ionospheric VLF‐propagation conditions night and day. Therefore the decrease of pulse‐rate from night‐level to day‐level is synchronized with sunrise, the increase from day‐ to night‐level with sunset. In the summer‐time to the simple day‐night‐cycle of winter‐time an additional afternoon‐maximum is superimposed with maximum‐time at 15 to 16 hours LMT. This afternoon‐maximum is caused by thunderstorm‐activity on the European continent during this season. The mean max./min.‐ratio of pulse‐rates characterizing mean daily variations amounts to 6 for summer‐time and 3.3 for winter‐time. In spring and autumn daily cycle show transition forms between winter‐ and summer‐type. The pulse‐rate‐quotient of both the amplitude‐stages qA2/Al=fA2:fA1 gives a criterion for the rate‐pulse amplitude‐distribution of atmospherics, he 10‐year monthly mean values of this quotient show no important annual cycle. The 10‐year‐mean amounts to qA1/A2 = 1–67.10‐2. Daily cycles in this pulse‐rate‐quotient are existent. One interesting fact of these daily cycles is the morning minimum short after sunrise which exists during the whole year. Together with the morning decrease of pulse‐rate this minimum of the quotient should be discussed as a possible “triggering pulse”; for the 24‐hour‐cycles in living organisms (Lotmar, et al., 1969; Wever, 1968).