Ana Maria Duran-Quesada
University of Costa Rica
APPLICATIONS OF LAGRANGIAN TRAJECTORIES ANALYSIS FOR MOISTURE TRANSPORT STUDIES
A Lagrangian methodology was used for the dynamical identification of the moisture sources associated with precipitation in Central America and two highly vulnerable ecosystems to be Monteverde Cloud forest and Cocos Island. The structure, annual cycle and interannual variability of the moisture sources were analyzed. It was found that both activity and contributions from the sources follow an annual cycle which defines the wet and dry seasons in Central America by means of the moisture availability, transport and convection. On inter-annual scales, variability was found to be dominated by the El Niño-Southern Oscillation. However the influence of other modes was also found. North Atlantic Oscillation seems to affect regional moisture transport through the forcing exerted by the NASH (North Atlantic Subtropical High) in the Caribbean. Variations in convective activity, the Inter Tropical Convergence Zone and the Caribbean Low Level Jet (CLLJ) may represent the response of the regional climate system to the forcing of the Madden-Julian Oscillation. Low frequency variability is also suggested to affect a terrestrial remote source found to be of importance for late spring summer moisture availability.
The atmospheric transport in the Intra Americas Seas region is fundamental for local and regional scale interaction processes. Among the main features of regional climate, the CLLJ has been found to be key regarding transport and precipitation. The three dimensional structure of the CLLJ as the wind flow approaches Central America was studied. The analysis of this structure in terms of its features and other dynamical fields allows the identification of the forcing for the transport of moisture. A conceptual model is proposed to provide further information on the dynamics of the moisture transport associated with the CLLJ. The analysis considers both the annual cycle and inter annual variability to study the effect of forcing due to variability modes. Aspects of the role of the CLLJ for the cross-isthmus moisture transport and the extra-tropical moisture export are mentioned as of importance for further study.