# Extreme Droughs in the Peruvian Amazon Region (2000-2024)
## 4 Discussion
These diurnal variations are related to the cloud cover and precipitation characteristics of the different seasons throughout the year, which differ for every region and are closely related to the climatological conditions of dry or wet periods. This suggests that the annual cycle of the main components of the surface radiative balance depends on the possible drought condition, so in the present work, the possible changes in the cycle related to this phenomenon are investigated. The monthly evolution of sensible and latent heat fluxes and solar radiation was analyzed during years of extreme and moderate drought, comparing them with climatological cycles in LOR1, UCA, and MD. The climatological cycles of sensible and latent heat are similar across the regions, although LOR1 has lower values, and they were higher for MD, coinciding with their precipitation levels. In extreme droughts, absolute maxima are observed in August and notable differences in the bulk Bowen ratio. To understand the particularities of each drought period, Figure 11 shows the distribution by month of the water deficit in every HY classified as extreme or moderate drought, as estimated by CHIRPS-ERA5. The panels in the right column contain the clustered bar distributions for the extreme and moderate drought years, and the left panel contains the distributions for the corresponding preceding year. In all cases, the water deficit was obtained mainly in the dry season, in the months of May-August, and the higher WD values were concentrated in August and July. However, in every case, there is a contribution of WD from the first month of the HY that has a degree of continuity with the preceding year. In the period 2004-2007, a continuity of WD conditions can be noticed from the dry season of 2004, which contributed to the extreme drought in 2004-2005, corresponding with Central Pacific El Nino conditions and relatively dry conditions at the beginning and the end of the 2005-2006 HY, leading to the moderate drought of 2006-2007, also favored by Central Pacific El Nino conditions at the beginning of the HY, from September to February. However, most of the WD occurred in the dry season, coincident with the Central Pacific La Nina, but moderately high Tropical North Atlantic temperature ([[https://www.worldclimateservice.com/2024/09/11/tropical-north-atlantic-index/](https://www.worldclimateservice.com/2024/09/11/tropical-north-atlantic-index/)]([https://www.worldclimateservice.com/2024/09/11/tropical-north-atlantic-index/](https://www.worldclimateservice.com/2024/09/11/tropical-north-atlantic-index/))), accessed on 15 January 2025. In the case of 2004-2005, El Nino conditions were also present at the beginning of the HY, switching to La Nina in the dry season, but the Tropical North Atlantic temperature in this period was very high, which favored an extreme drought. In the cases of 2009-2010 and 2015-2016, it is also observed that the preceding year was affected by significant WD in the dry season. The period of 2022-2024 has been the most severe in the century, with continuous dry conditions since July 2022, when a very dry period extended to September, ending as the very dry HY of 2022-2023 with the highest WD in the dry season of 2023. This occurred after the 2021-2022 HY totally covered by Central and Eastern Pacific La Nina, extending until February 2023, when a swift switch to El Nino conditions occurred, prevailing until the beginning of 2024, together with very high air temperatures, as discussed by [2; 3], and in relation to the drought conditions and heatwaves [59] in the entire Amazon basin. The HY of 2023-2024 began as moderately dry in September, but the WD was again very high in the dry season, from May to August. It is interesting to evaluate the influence of precipitation and evapotranspiration uncertainty on the results of the present paper.