On some characteristics of tropical atmospherics due to monsoon clouds

The field intensity of VLF-atmospherics recorded over the tropical station, Calcutta (22°34′N, 88°24′E) occasionally exhibit a characteristic fall in association with the ground rainfall during monsoon months. The sudden fall is followed by a pause and a subsequent recorvery thus forming a clipped saw-tooth like appearance. The occurrences and magnitudes of the fall are predominant at 20 kHz in the VLF-band. They mostly occur around local noon and midnight hours.