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Ann. Geophys., 24, 2793-2808, 2006
www.ann-geophys.net/24/2793/2006/
© European Geosciences Union 2006
A numerical study of cell merger over Cuba – Part II: sensitivity to environmental conditions
D. Pozo1, I. Borrajero2, J. C. Marín1, and G. B. Raga1
1Centro de Ciencias de la Atmósfera, UNAM, México, Ciudad Universitaria, México, DF, 04510, México
2Instituto de Meteorología de Cuba, Loma de Casablanca, Regla, C. Habana, Cuba
Abstract. In the first part of this study, an external 3-D ambient field
(3d-field) was used to initiate a simulation (Sim1). In this paper, the
influence of the 3-D field in the occurrence of the cloud merger simulated in
Sim1 is studied. The surface convergence was very important to supply the
lifting necessary for the development of new the convection. The interaction of
the gust front from an old cloud with the environmental wind, as well as the
interaction between the two gust fronts, were the main factors that enhanced the
surface convergence. A favorable perturbation pressure gradient was also
found to intensify this mechanism. The formation and development of a new
cloud from the cloud bridge was the main feature for the occurrence of the
cloud merger.
The influence of the wind shear components and the relative humidity (RH) in
the occurrence of the cloud merger was also analyzed. The parallel wind
shear component and the large RH present in the zone of study had a positive
contribution to the occurrence of the cloud merger. However, the
perpendicular wind shear component did not provide the main forced lifting
which would be capable of generating the new convection along the direction between
interacting clouds.
A high resolution simulation corroborated that the cloud merger was
correctly simulated and it was not obtained by unrealistic effects due to
the coarse resolution employed. It evidenced that when the horizontal
resolution is improved, the life cycle of each cloud and the different
processes related to their interactions are better described.
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