Unearthing the source of anomalous moisture and temperature excesses for the record-breaking 2023 Amazon drought

The record-breaking 2023 Amazon drought, considered a once-in-a-century event, was not generally due to a moisture deficit from either remote sources or from the Amazon Basin itself. Rather, it was caused by the almost complete absence of atmospheric instability which inhibited convection and therefore precipitation in this region and by extremely high temperatures. Although atmospheric moisture was anomalously high, it was insufficient to compensate for high temperature, which led to reduced relative humidity values and enhanced atmospheric evaporative demand. Furthermore, the moisture that did not precipitate in the region due to atmospheric stability was transported to areas where there was sufficient instability for convection (i.e. moisture sinks), resulting in very high precipitation and floods in La Plata river basin in September 2023. The temperature anomaly over the target region presents two sources, a local one contributing to warming and an external one contributing to cooling. The results show the importance of adiabatic warming due to subsidence in the region itself (atmospheric stability) and also outside (anticyclonic circulation).