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Orographic precipitation in the tropics: experiments in Dominica

Smith, R. B., Schafer, P., Kirshbaum, D. J. and Regina, E. (2009) Orographic precipitation in the tropics: experiments in Dominica. Journal of the Atmospheric Sciences, 66 (6). pp. 1698-1716. ISSN 1520-0469

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To link to this item DOI: 10.1175/2008JAS2920.1


The “natural laboratory” of mountainous Dominica (15°N) in the trade wind belt is used to study the physics of tropical orographic precipitation in its purest form, unforced by weather disturbances or by the diurnal cycle of solar heating. A cross-island line of rain gauges and 5-min radar scans from Guadeloupe reveal a large annual precipitation at high elevation (7 m yr^{−1}) and a large orographic enhancement factor (2 to 8) caused primarily by repetitive convective triggering over the windward slope. The triggering is caused by terrain-forced lifting of the conditionally unstable trade wind cloud layer. Ambient humidity fluctuations associated with open-ocean convection may play a key role. The convection transports moisture upward and causes frequent brief showers on the hilltops. The drying ratio of the full air column from precipitation is less than 1% whereas the surface air dries by about 17% from the east coast to the mountain top. On the lee side, a plunging trade wind inversion and reduced instability destroys convective clouds and creates an oceanic rain shadow.

Item Type:Article
Divisions:Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:4640
Uncontrolled Keywords:Rainfall, Orographic effects, Diurnal effects, Tropics
Publisher:American Meteorological Society

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