| Popis: |
A study is made of local wind development in New Zealand alpine valleys. The general characteristics of alpine airflow regimes are examined using both climato logical and case study approaches. Thermo topographic and dynamic effects are the major influences on valley airflow, the relative significance of each varying spatially as well as seasonally and diurnally. Case studies show that clear relationships exist between micro meteorological characteristics within an alpine valley and the phases of local wind development. In particular, boundary layer stability and energy flow characteristics are seen to vary with different phases of local wind development. The examples studied illustrate basic characteristics of local airflow, but particularly the development of nocturnal mountain winds with a transition to daytime up-valley flow. The airflow shows classic local wind characteristics, regarding depth, speed, and return currents. An intermediate layer frequently occurs between the alpine valley wind regime and the gradient flow above. This layer of generally light winds may be persistently north-westerly and the result of regional dynamic forcing of the gradient wind. Alternatively, under weak gradient airflow, it may exhibit variability indicating regional thermal forcing. |
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