Diabatic Heat Effects on the Generation of Energy for Evolution of a SACZ Event: A Perspective from the Lorenz Energy Cycle

Here we used meteorological data sets from ERA-5 reanalysis to study the dynamic and thermodynamic characteristics of a SACZ event that occurred between December 12 and 26, 2013. This is an atypical SACZ episode with considerable variations in cloudiness band positioning and high rainfall amounts, causing enormous problems for society. We study this case through the Lorenz Energy Cycle (LEC), focusing mainly on the role of diabatic heating in energy generation and consequently in circulation aspects, analyzing the event in three stages (formation, development, and dissipation), and discussing it according to the convection localization pattern. The diabatic heat rate has a large impact on the energy generation of SACZ events at midlevels south of 24°S and below 900 hPa in the tropics. In LEC, the generation terms in the SACZ area were larger at the beginning (December 12-15) and smaller at the ending periods (December 23-26), with means of 21.23 and −7.62 W/m2, respectively. The conversion terms follow the LEC directions, except for barotropic instability [C(KE,KM)<0] that dominates throughout the analyzed periods. The convection area expansion to the north between December 16-22, was reflected by the most intense heating in the tropics and weaker barotropic instability. The friction term did not favor the event decay; therefore, we concluded that the cooling through a negative covariance between Q and T contributed to the event decay. We find that these results were largely influenced by a midlatitude wave train configuration that acted to favor the persistence, expansion, and decay of the event.