THUNDERSTORMS

New Zealand Herald, Volume LXXVI, Issue 23413, 1 August 1939, Page 13

THUNDERSTORMS

Sir, —Your correspondent "E.C.D." asks why thunderstorms do more damage nowadays than was the case in our childhood days. My conviction is that the progressive forest destruction is the cause of the increasing violence of thunderstorms and "cloudbursts," both of which are electrostatic phenomena. The clords and the earth form the two plates or surfaces of a huge electrostatic condenser, and the "capacity" of this condenser to hold electric energy and thus to induce discharges of electricity and rain is enormously increased by the presence of forests. The numerous leaves, twigs, and branches of the trees provide a vast surface or area to hold the "condensed" electric charge. For this reason a forest-covered land compels the clouds to discharge their electricity and rain when high up. so enabling the electric charges and the rain to be dissipated over a large area and thus do no damage. It is obvious that the larger the area over which the cloud dissipates the electric discharge and rain, the lols is the likelihood of damage from either.

Where or when the land is bare —clue to forest destruction—the electrostatic capacity of such bare land to hold condensed electrical charges is greatly reduced, so that the rainclouds have to descend very loir before the electrostatic capacity is strong enough to cause a discharge between cloud and earth. Under such circumstances the lightning must necessarily discharge over a very small area and do great damage, and likewise the rain, precipitated from such a low lying cloud, must necessarily be in the form of a sudden and dangerous "cloudburst" over a very small area of land surface. In both cases, the intensities of the discharge of electric energy and rain increase inversely as the square of the height from cloud to earth, Thomas A. F, Stoxe.