MESOSCALE ASPECTS OF OROGRAPHIC INFLUENCES ON FLOW AND PRECIPITATION PATTERNS

Since horizontal dimensions of orography in relation to cloud formation and development are mostly in the mesoscale, we usually observe mesoscale nephsystems in areas with topographic influences. In addition to their barrier effects, mountains during the daytime act as effective high-level heat sources or as cloud generators. At night, however, they suppress the cloud formation and act as cloud dissipators. When these effects are combined with the height of the convective cloud base, which could be either higher or lower than that of the mountains, the patterns of orographic neph systems and precipitation are quite complicated. By using actual cases of cloud and precipitation measurements, detailed climatological and mesosynoptic patterns of clouds and precipitation are discussed.