Effect of Sado Island on Snowfalls in Niigata Plain

So-called “Sado Block” effect

Abstract

It is widely believed that so-called "Sado Block" reduces snowfalls (produces snow-shadow) in Niigata City. This study investigates the mechanism of this snow-shadow. Statistical analysis of long-term radar data showed that the snow-shadow was found always downwind of Sado Island. Numerical experiments showed that snowfall over the Niigata Plain would be lighter with the island than without it. Also, Sado Island reduced heat fluxes from the sea surface by weakening leeward winds and reduced water vapour and cloud water over the leeward sea due to reduced moisture advection. This is likely the primary mechanism of the "Sado Block".