Abstract
The present study aims to determine the factors influencing the transition from shallow to deep convection in the trade winds region using an observational approach, with emphasis in the Yucatan Peninsula in eastern Mexico. The methodology is based on a discrimination of two regimes of convection: a shallow cumulus regime, usually with little or no precipitation associated, and an afternoon deep convection regime, with large amounts of precipitation, preceded by a short period of shallow convection. Then, composites of meteorological fields at surface and several vertical levels, for each of the two convection regimes, are compared to infer which meteorological factors are involved in the development of deep convection in this region. Also, the relationship between meteorological variables and selected regime-transition parameters is evaluated only for deep convection regime days. Results indicate the importance of dynamic factors, such as the meridional wind component, in the transition from shallow to deep convection. As expected, thermodynamic variables, such as the low-level specific humidity in the shallow cumulus layer, also contribute to the regime transition. The presence of a southerly component of wind at low- to mid-levels during the early morning in deep convection days provides the shallow cumulus with a more favorable environment so that transition can occur, since abundant moisture from the Caribbean is supplied through this prevailing southern wind. The results can be relevant for reducing uncertainties regarding some important parameters in global and regional models, which could lead to improved simulations of the transition from shallow to deep convection and precipitation.
Highlights
Convection over land in tropical regions shows a characteristic pattern throughout the diurnal cycle, presenting shallow cumulus in the morning, which grow during the early afternoon transitioning to deep convective clouds, with the development of precipitation
In this study we focus on the transition to deep convection in the Yucatan Peninsula in eastern
We address here the problem of the transition from shallow to deep convection over the Yucatan Peninsula from an observational point of view
Summary
Convection over land in tropical regions shows a characteristic pattern throughout the diurnal cycle, presenting shallow cumulus in the morning, which grow during the early afternoon transitioning to deep convective clouds, with the development of precipitation. While rainfall in the tropics may be synoptically-controlled or driven by large-scale dynamics, we concentrate on cases when little (or no) synoptic forcing affects the area of interest, in order to isolate the process and explore the mechanisms that control the transition from shallow to deep convection The interest in this region is mainly due to two reasons: (i) Despite the homogeneity of the land surface, the proximity of two important basins (the Caribbean Sea and the Gulf of Mexico) and the different wind regimes add complexity to convection over the peninsula, and (ii) during summertime—under no significant synoptic influence—two regimes of convection coexist: a shallow cumulus regime, mostly with no precipitation associated; and a late afternoon deep convection regime, with large amounts of precipitation associated and a short period of shallow convection preceding it. The results will be useful in order to improve the understanding of the controls on deep convection in tropical land regions, which is still poorly understood
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
