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A model of the feeder–seeder mechanism of orographic rain including stratification and wind‐drift effects
Author(s) -
Carruthers D. J.,
Choularton T. W.
Publication year - 1983
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49710946109
Subject(s) - orographic lift , airflow , stratification (seeds) , meteorology , environmental science , atmospheric sciences , precipitation , wind direction , geology , wind speed , hydrostatic equilibrium , hydrology (agriculture) , physics , geotechnical engineering , seed dormancy , germination , botany , quantum mechanics , dormancy , biology , thermodynamics
Orographic enhancement of rain via the ‘feeder‐seeder’ mechanism has been calculated using a stratified airflow model. The effect of wind drift on precipitation has been included. Comparisons have been made using potential flow models both in two and in three dimensions and in the model of M. J. Bader and W. T. Roach. For high windspeeds (≥ 15ms −1 ), when large enhancements occur, the potential flow treatment is sufficient. Inclusion of stratification does not significantly affect the total washout, although in the case of long hills (half‐length ≥ 10km) the precipitation maximum is moved upwind. For long hills the results are also in close agreement with the model of Bader and Roach. Over shorter hills both wind drift and non‐hydrostatic effects are important. Wind drift decreases both maximum and total enhancements. The Bader and Roach airflow formulation is inaccurate since it overestimates streamline displacements over the hill. Three‐dimensional effects are small except over short steep hills.