Multiscale Spatiotemporal Variations of Precipitation-topography Relationship over Mountainous Complex Terrain

The current study conducted some investigations into the spatia-temporal structure of the precipitation-topography relationship (P-T relationship) over mountainous complex terrain, especially in convective precipitation events, through a statistical approach based on weather radar observations and a physically based numerical approach using a mesoscale meteorological model. An investigation based on radar observations showed that the precipitation-elevation correlation has a Gaussian-functional variation in a region corresponding to the windward slope of an isolated mountain, although there are some cases to show an exponential relationship named ECAT (Exponential Corre-lation of Accumulated precipitation with Topographic elevation). The Gaussian-functional relationship, which was found through diagnostic numerical simulations of the atmosphere on an isolated mountain, can be created even on the actual complex terrain especially on a windward mountain slope, and named GCAT (Gaussian-functional Correlation of Accumulated precipitation with Topographic eleva-tion). The interrelationship between the ECAT and GCAT was explored based on diagnostic numerical simulations and found to be explained by the superposition of the P-T relationship. The superposition-produced P-T relationship can show either a curvilinear or linear relationship according to the form of each superposed P-T relationship. This means that the functional form of the temporal-average P-T relationship in a certain period depends on what degree of variations the short-term P-T relationship has in its functional form within the period, and it tends to be closer to the ECAT when the variation is sufficiently large. In other words, the ECAT is created over mountainous complex terrain by the spatial and temporal superposition of the GCAT created on a mountain slope, when the spatial and temporal scales of the P-T relationship are as large as the Meso -scale atmospheric disturbances.