Characterization of the Atmospheric Conditions and Cloudiness Leading to Extreme Rainfall Events over the Northern South America Andean Region: An Approach Using High Resolution data from GOES-ABI and ERA-5

Antioquia is a department of Colombia, located in the northwest corner of South America. Its complex topography, associated with the branches of the Andes Cordillera, and the interplay of different mechanisms result in a highly variable precipitation distribution and cloud cover over the region. Historically, extreme rainfall events over the region have resulted in flooding, landslides, and other phenomena affecting the population. The recent launch of the GOES-16 satellite and especially the availability of the ABI data represents an excellent opportunity to broaden the understanding of the processes associated with this variability. This study aims to provide an in-depth spatio-temporal analysis of cloud cover over Antioquia and to examine the life cycle of extreme rainfall events that occurred during 2018. To achieve the first goal, we used VIS and IR data, RGBs composites, and level2 products derived from ABI. A lagged composite analysis of several variables from ERA-5 reanalysis and some ABI products was carried out to achieve the second goal. The results show a coherent relationship between the occurrence of heavy rainfall events and the presence of geopotential and velocity potential anomalies over the north of South America and westerly wind anomalies from the Pacific Ocean and the Caribbean Sea, in different pressure levels. The enhanced influx of moisture driven by this pattern favors convergence over Antioquia, increasing the probability of rainfall. The results for 2018 are compared with the meteorological conditions leading to extreme rainfall events in Antioquia over the period 1998-2018, obtained using the TRMM-3B42-V7 dataset. Early identification of cloud top transition phases between low-altitude clouds (with water droplets) and high and deep clouds (with ice particles) is a good indicator of convective development for events occurring before sunset. The most significant convective development occurs towards the eastern and north-eastern Antioquia, and over Chocó and the western Antioquia, with cumulonimbus anvils associated with heavy rains. Results also include an annual average climatology of cloud cover, the cloud top temperatures, the cloud phases, and convection.