Analysis of nocturnal cold-air currents formed in Satoyama (urban-neighboring hills and forests) using airborne MSS data and CFD simulation

This paper presents a method to make a good use of airborne MSS data as boundary conditions for simulating cold currents formed within a valley with forest during the summer nighttime. The data used in the analysis was the MSS (multispectral scanner) data observed in an urban area with suburban hills and forests. From results of analyzing the relationship between topographic features and nighttime surface temperature distributions in the observed area, a valley where a residential area is located and the nocturnal cold current occurs was selected for CFD (Computational Fluid Dynamics) simulation. As input boundary conditions, surface temperatures from the MSS data were used in the CFD simulation. Simulation results show that cold currents developed above the valley slopes flow down toward the bottom of the valley, and their air temperature distributions can be quantified.