Characterization of convective storms in Northern South America using GOES16 ABI infrared information: An improved detection and tracking algorithm

Northern South America is a region that experiences one of the highest occurrence frequencies of convective storms in the tropical region, triggering several natural hazards like floods, landslides, hailstorms, and lightning strikes, among others. The combination of some factors affects this kind of convective system's genesis and occurrence: tropical location, the orographic effects of the Andes mountain range, and the regional atmospheric dynamics and local thermodynamic preconditions. An improved tracking algorithm was developed and implemented to identify and track convective clouds in northern South America, identifying systems from their early stages of development. The algorithm uses the ABI 13 band brightness temperature data from 2018 to 2022. The morphology and spatiotemporal features of the cloud systems were characterized using parameters such as area, duration, minimum brightness temperature, and brightness temperature decrease rate. In addition, the assessment of environmental conditions was performed by using ERA5 reanalysis data, where the characterization was based on high values in the probability distribution function of the parameters mentioned above.

The results show that approximately 90% of the identified events had maximum areas of 15,000 km², with median and mean durations of 40 and 59 minutes, respectively, and are characterized by average brightness temperatures of -75°C and average cloud top temperatures cooling rates of -0.65°C/min, which are higher than for systems with higher extensions. The importance of these storms lies in the fact that despite their short lifetimes, they are responsible for many of the intense events that occur in the region. Moreover, it was found that the higher density of convective clouds in the initiation stage is between 21:00 UTC and 01:00 UTC, modulated by the diurnal cycle, atmospheric conditions, and local topographic effects. The mature stage occurs around 05:00 UTC, according to minimum brightness temperature values. On the other hand, the lower density of convective events in their early stages can be observed in the base of the inter-Andean valleys because initiation mechanics of convection take advantage of slopes of the orography and its interaction with regional and local circulation.