Abstract
The purpose of this study is to clarify precipitation-topography relationships (PTRs) in mountainous regions on various spatiotemporal scales and to determine the physical mechanism of them. By running numerical simulations under realistic conditions using mesoscale model MM5, the PTRs in the Kinki region of Japan were investigated. PTRs on a spatial scale of a mountain slope were found to be described with a Gaussian-type function, which is referred to as GRIM (Gaussian-functional Relationship on an Isolated Mountain). And one of the conditions required for the formation of GRIM was determined: GRIM can be formed when regional average rainfall is more than 10 to 20 mm on a mountain slope. The spatiotemporal fluctuations of GRIM were, then, investigated to clarify how GRIM is connected with large-scale PTRs. As a result, large-scale PTRs were found to be formed by the summation of GRIM's. And it was clarified how large-scale PTRs vary according to the fluctuation properties of GRIM.
