In order to clarify the diminution characteristics of terrestrial gamma ray exposure rate due to snow cover, measurements were performed on the ground with and without snow cover. The diminution factors observed were 0.36-0.17 for 12-23g/cm2 of water equivalent of the snow cover. According to a calculation by the Monte Carlo method, the corresponding diminution factors were 0.32-0.16. They agreed well as a whole, while the fluctuation of the diminution factors based on the measured exposure rate were fairly large. The fluctuation is deemed to be due to the inhomogeneity in the distribution of the snow cover as well as the gamma ray field. The fluctuation is expected to decrease with increase in the degree of their homogeneity.
