Importance of thermodynamic conditions in extreme precipitation events in the city of Belem and metropolitan region

Abstract

The objective of this research was to verify the importance of thermodynamic factors in the occurrence of extreme precipitation events in Belém (PA) and metropolitan region, from August 2008 to December 2009. The study of the thermodynamics of the atmosphere was carried out in the light of theories of the Potential Available Energy for Convection (CAPE) and Convection Inhibition Energy (ISCED). In order to classify the extreme precipitation events, the decision method was used to associate them with the CAPE and the ISCED values. It was observed that the studied region has strong convective activity throughout the year, and that not always high CAPE and low ISCED produces precipitation. This situation determines deep convection, but to have precipitation there is a need for the dynamic forcing, even for the occurrence of extreme rainfall events in the rainy period, the dynamic forcing is ITCZ, and in the dry period what contributes is the Instability Line (LI). So when the precipitation process depended exclusively on the CAPE, it was necessary a high value to generate deep convection and consequently precipitation, whereas, in the process of precipitation with dynamic contribution, a significant value of CAPE was not necessary.

Extreme rainfall events in the West African Sahel: Understanding storm development over the Damergou gap using convection‐permitting simulations in the Weather Research and Forecasting model

“…Other extreme rainfall studies outside of West Africa have noted a similar finding (e.g., McCorkle et al, 2016;Gille and Mota, 2018) as storms with high CAPE are more likely to have deeper, stronger updrafts and be associated with cold-rain processes that are less efficient than warm-rain processes (Hamada et al, 2015;Hamada and Takayabu, 2018). This indicates that other factors should be considered instead of relying on CAPE to determine if an event is likely to produce extreme rainfall.…”

“…Our analysis demonstrates that it is possible for extreme rainfall to occur in a weakly unstable environment (e.g., <2,000 J·kg −1 ). Other extreme rainfall studies outside of West Africa have noted a similar finding (e.g., McCorkle et al ., 2016; Gille and Mota, 2018) as storms with high CAPE are more likely to have deeper, stronger updrafts and be associated with cold‐rain processes that are less efficient than warm‐rain processes (Hamada et al ., 2015; Hamada and Takayabu, 2018). This indicates that other factors should be considered instead of relying on CAPE to determine if an event is likely to produce extreme rainfall. Local convection ahead of an approaching MCS is an important factor to consider for extreme rainfall.…”