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Communication incl. Poster: BibTeX citation key:  Yu
Yu, J. & Grandpeix, J.-Y. 2009. A new parametrization of sub-grid scale orography thermal effect on deep convection triggering. Work presented at Third International AMMA Conference, July 20—24, at Ouagadougou, Burkina Faso.
Added by: roussot 2009-11-04 19:11:16
Categories: Atmospheric processes, Land surface-atmosphere feedback
Keywords: Atmospheric Boundary Layer, Clouds - Convection
Creators: Grandpeix, Yu
Publisher: African Monsoon Multidisciplinary Analyses (Ouagadougou, Burkina Faso)
Collection: Third International AMMA Conference

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Numerous observations show that the formation of deep convection systems over complex terrain is frequent and can often result in important quantity of precipitation. A recent analysis of satellite data (Thomas Fiolleau, Rémy Roca, Jean-Yves Grandpeix and Jingmei Yu, 2nd AMMA conference, 2007, Karlsruhe) over the African Monsoon region reveal that during the monsoon season, the convection genesis frequency significantly higher over the mountain than the plains. The statistics show that the genesis frequency exhibits a diurnal cycle with its maximum arround 3pm local time. The statistics also show that there exists a positive correlation between mountain elevation and convection genesis frequency.
We introduce a new parametrization in order to represent in GCM the sub-grid scale orography thermal effect on deep convection initiation. The model represents a mountain breeze, a process due to the horizontal temperature contrast between environment and mountain slope surface heated by the sun. The model breeze consists in one individual ascending column of fixed width (100m, the approximite scale of the surface layer depth). The model computes the maximum kinetic energy of the breeze in a GCM grid, associated with the maximum radiation arriving on the mountain slopes, which is estimated by a algorithm which take into account the sub-grid mountain elevation and the slope orientation. In the case where the kinetic energy of the mountain breeze exceeds the convective inhibition, the GCM deep convection scheme is triggered.
The parametrization has been implanted in the LMDZ4 GCM. The main features of the simulated mountain breeze will be presented, together with the spatial and temporal distribution of deep convection triggered by mountain breeze.
Added by: roussot