19 Dec 2022
19 Dec 2022
Status: this preprint is open for discussion and under review for Climate of the Past (CP).

Multidecadal variability of the ITCZ from the Last Millennium Extreme Precipitation Changes in Northeastern Brazil

Isela Leonor Vásquez P.1, Humberto Alves Barbosa2, Gilvan Sampaio1, César Arturo Sánchez P.3, Giselle Utida4, David Pareja Quispe5, Juan Gregorio Rejas Ayuga6,7, Hugo Abi Karam8, Jelena Maksic1, Marília Harami Shimizu1, and Francisco William Cruz4 Isela Leonor Vásquez P. et al.
  • 1Weather Forecast and Climate Studies Center ,CPTEC. National Institute for Space Research (INPE), Brazil
  • 2Federal University of Alagoas (UFAL), Brazil
  • 3Applied Computing (CAP), National Institute for Space Research (INPE), Brazil
  • 4Geosciences Institute, University of Sao Paulo (USP), Brazil
  • 5Department of Interdisciplinary Physics, National University of San Marcos (UNMSM), Peru
  • 6Department of Space Programs, National Institute for Aerospace Technology (INTA), Spain
  • 7Technical University of Madrid (UPM), Spain
  • 8Geoscience Institute, IGEO, Federal University of Rio de Janeiro (UFRJ), Brazil

Abstract. Decadal and multidecadal variability of the Intertropical Convergence Zone (ITCZ) is analyzed in space-time using CMIP6 simulations and paleoprecipitation records during the Last Millennium. We investigated the persistence patterns of the CMIP6 ensemble models, using low frequency component analysis (LFCA) to isolate the mechanisms that modulate the ITCZ at the multidecadal scale. The results suggest that the north-south displacement of the ITCZ was related to the oceanic region with the highest sea surface temperature (SST) of the tropical South Atlantic basin. The zonal mode variability is initially associated with the equatorial region (between 5° S and 5° N) and with the northwestern African coast. These observations also contrast with the paleoclimatic records of the region, indicating a northward shift of the ITCZ during the MCA and a southward shift during the LIA. Based on the periodicities observed the 21 years is predominant during the Last Millennium can be associated with the solar cycle influence on the pattern of ITCZ contracted and positioned in the central region of the equator. This relationship suggests that, although ENSO is the main driver in variability over Tropical South America at interannual time scales, this influence can be significantly modulated by longer time scales. The results suggest the existence of a low-frequency variability, modifying the distribution of precipitation and with consequences in the intensity and frequency of droughts/floods events in the NE, indicating that these events are associated with the coupling between the oceans and the atmosphere.

Isela Leonor Vásquez P. et al.

Status: open (until 13 Feb 2023)

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Isela Leonor Vásquez P. et al.

Isela Leonor Vásquez P. et al.


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Short summary
We wonder if the simulations of the CMIP6 models represent the multidecadal variability of precipitation associated with the position of the ITCZ? We analyzed the outputs of the CMIP6 models together with paleoclimatic records from reconstructed multiproxy data from South America. Our results show that the north-south shift of the ITCZ ​​maintains a relationship with the oceanic region with higher sea surface temperature (SST) in the tropical river basin of the South Atlantic.