Observed Gamma Ray Radiation Variations Associated with Tropical Zone Rainfall Events

Abstract:

Major liquid precipitation events are associated with changes in measurable natural nuclear radiation at ground level. We have observed that gamma radiation from airborne constituents varies with weather conditions, especially rainfall events, as observed with ground level instrumentation at near tropical zone low latitudes. Simultaneous observations of natural gamma ray emissions at the ground level and tropical zone rainfall variation observations have been performed in Sao Jose dos Campos, Sao Paulo, Brazil with temporal resolution accuracy of the order of one minute. This has allowed a detailed comparison of rainfall amounts and monitored gamma ray emission time profiles to estimate the actual radionuclide concentration in the rainwater. The radionuclide fallout time profiles were numerically simulated from the observed gamma rate through a numerical minimization procedure. The radionuclide concentration was calculated as a ratio of the simulated fallout to that of the observed rainfall amounts. Our result shows an anti-correlation between the average values of these parameters at times. The effect is especially pronounced at rapid rainfall onsets. The results obtained are compared with the current models and data, and the causes are discussed. Future research will study gamma ray radiation versus weather events at ground level in the temporal zone (North America) where the natural background radiation is thought to be generally somewhat lower than at ground level on the South American continent.