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ABSTRACT Composite analysis of the atmospheric mechanisms in South Atlantic explosive cyclones was performed utilising ERA5 reanalysis for the 2010–2020 period. By a manual tracking method, 271 cases were found (127 weak, 104 moderate and 40 intense). The cyclones follow the preferential displacement from northwest to southeast. There is a trend that, as the explosive cyclone's intensity increases, its trajectory becomes less zonal and has a more significant impact in the coastal areas of Southern Brazil and Uruguay. These intensity frequencies were discretized through a compositing technique for studying explosive cyclones. The results revealed that explosive cyclones begin following the classical model from Bjerknes and Solberg, and, at the end of the explosive phase, they tend to become Shapiro–Keyser type, especially in moderate and intense ones. Vertical movements appeared more significantly at the beginning of the explosive stage. It was observed that intense explosive cyclones transition from the equatorial side of the high‐level jet to the polar side. In addition, surface latent heat flux may significantly impact the cyclone's development both in the beginning and during the explosive phase, especially in intense systems. A horizontal dipole pattern is seen for surface sensible heat fluxes, as the ocean loses and gains heat in the cold and warm sectors, respectively, at roughly the same amount. [ABSTRACT FROM AUTHOR]

Evapotranspiration (ET) is an important component of the hydrological cycle. Understanding the ET process has become of fundamental importance given the scenario of global change and increasing water use, especially in the agricultural sector. Determining ET over large agricultural areas is a limiting factor due to observational data availability. In this regard, remote sensing data has been used to estimate ET. In this study, we evaluated the Moderate-Resolution Imaging Spectroradiometer (MODIS) land surface ET product estimates (hereafter MOD16 ET – MODIS Global Terrestrial Evapotranspiration Product) over two rice paddy areas in Southern Brazil, through the ET measured using the eddy covariance technique (hereafter EC). The energy balance components were evaluated during fallow and flooded seasons showing latent heat flux dominates in both seasons. The results showed that MOD16 ET underestimated EC measurements. Overall, the RMSE (root mean square error) ranged between 13.40 and 16.35 mm 8-day−1 and percent bias (PBIAS) ranged between −33.7% and −38.7%. We also assessed the ET (measured and estimated) main drivers, with EC yielding higher correlation against observed net radiation (Rn) and global radiation (Rg), followed by air temperature (Temp) and vapor pressure deficit (VPD), whilst MOD16 ET estimates yielded higher correlation against leaf area index (LAI) and fraction of photosynthetically active radiation (fPAR). The MOD16 algorithm was forced with meteorological measurements but the results did not improve as expected, suggesting a low sensitivity to meteorological inputs. Our results indicated when a water layer was present over the soil surface without vegetation (LAI around zero), the largest differences between EC measurements and MOD16 ET were found. In this period, the expected domain of soil evaporation was not observed in MOD16 ET physical processes partition, indicating the algorithm was not able to detect areas with high soil moisture. In general, the MOD16 ET product presented low accuracy when compared against experimental measurements over flooded rice paddy, suggesting more studies are necessary, in order to reduce uncertainties associated to the land cover conditions. [ABSTRACT FROM AUTHOR]