Moisture quasi-equilibrium theory postulates that the instability index, a measure of low to mid-tropospheric moist convective instability, is inversely proportional to saturation fraction, a good proxy for precipitation. We looked at thermodynamic properties for 16 convective events from dropsonde data collected during the field project Organization of Tropical East Pacific Convection (OTREC). OTREC2019 performed 22 flights in the Eastern Pacific and Southwest Caribbean out of Costa Rica using the NSF/NCAR Gulfstream V aircraft. Convective available potential energy and saturation fraction show weak anti-correlation, while the instability index and saturation fraction are more strongly anti-correlated. This supports the moisture quasi-equilibrium hypothesis. Vertical mass flux profiles are calculated for all 16 convective events (8 convective cases in the tropical Eastern Pacific, 5 off the Pacific coast of Colombia and 3 in the Southwest Caribbean). Every developing convective case has a bottom-heavy vertical mass flux profile and every decaying case has top-heavy profile.

Two data sets (OTREC and PREDICT) and the European Center operational model are used to study convection. Vertically integrated moisture convergence is taken to be a proxy for convection. The interplay between the thermodynamic parameters is examined for weak and strong convection. It is found that for strong convection saturation fraction anti-correlates with instability index and DCIN in a similar manner for all analyzed regions of PREDICT and OTREC. The European Center model is used to look at the composite diurnal cycles of strong and weak convection. As convection increases, saturation fraction increases while instability index and DCIN decrease as in OTREC and PREDICT. The boundary layer and free troposphere thus both play an important role in convection development.

The systematic analysis of convection and the environment is performed for two field projects, OTREC and PREDICT by implementing 3DVAR on drospondes data sets. Vertically integrated moisture convergence is taken to be a proxy for convection. The interplay between the thermodynamic parameters is examined for three different stages of convection: strong convection, medium to weak and weak to null convection. It is found that for strong convection saturation fraction anti-correlates with instability index and DCIN in a similar manner for all analyzed regions of PREDICT and OTREC, while the differences in the environment become more pronounced as we move towards weak and null convection. ECMWF operational model is used to look at the time evolution of convection. As convection increases, saturation fraction increases while instability index and DCIN decrease. The boundary layer and free troposphere both play an important role in convection development in OTREC and PREDICT regions.

According to TRMM and GPM satellite precipitation composites, a broad maritime area over the far eastern Tropical Pacific and western Colombia houses one of the rainiest spots on Earth. This study aims to present a suite of mechanistic drivers that help create such a world-record breaking rainy spot. Previous research has shown that this oceanic and nearly-continental precipitation maximum has a strong early morning precipitation peak and development of a high density of mesoscale convective systems. We examined new and unique observational evidence highlighting the role of both dynamical and thermodynamical drivers in the activation and duration of organized convection. Results show the existence of a rather large combination of mechanisms, including: (1) dynamics of the Choco (ChocoJet) and Caribbean Low-Level Jets along their confluence zone, including the Panama semi-permanent low; (2) land breeze favors ChocoJet deceleration offshore, enhancing the nighttime and early morning low-level convergence; (3) vertical wind shear and tilting of vertical wind shear into vorticity lines that interact with convective outflows; (4) action of mid-level gravity waves, which support the strong diurnal variability; (5) mesoscale convective vortices related to subsidence in the stratiform region in long lasting MCSs reinforcing (3); and (6) the likely role of land surface-atmosphere interactions and the rainforest over western Colombia. This study emphasizes the multi-scale environmental processes associated with the formation of one of the rainiest spots on Earth and showcases new observations gathered during the Organization of Tropical East Pacific Convection (OTREC; August-September, 2019) which support the outlined mechanisms.

Gridded dropsonde analyses are made using data from the OTREC (Organization of Tropical East Pacific Convection) and PREDICT (Pre-Depression Investigation of Cloud-Systems in the Tropics) projects to characterize the mesoscale properties of tropical oceanic convection in terms of selected thermodynamic parameters computable from the explicit grids of large-scale models. In particular, column relative humidity, low to mid-tropospheric moist convective instability, and convective inhibition correlate with moisture convergence, while sea surface temperature is related to the top-heaviness of mass flux profiles and the integrated entropy divergence. Local (as opposed to global) surface heat and moisture fluxes and convective available potential energy have little relation to these quantities. These results provide useful constraints for cumulus parameterizations.