Espinoza J. C., Arias P. A., Moron V., Junquas Clémentine, Segura H., Sierra-Perez J. P., Wongchuig S., Condom Thomas. (2021). Recent changes in the atmospheric circulation patterns during the dry-to-wet transition season in South Tropical South America (1979-2020) : impacts on precipitation and fire season. Journal of Climate, 34 (22), 9025-9042. ISSN 0894-8755.
Titre du document
Recent changes in the atmospheric circulation patterns during the dry-to-wet transition season in South Tropical South America (1979-2020) : impacts on precipitation and fire season
Année de publication
2021
Auteurs
Espinoza J. C., Arias P. A., Moron V., Junquas Clémentine, Segura H., Sierra-Perez J. P., Wongchuig S., Condom Thomas
Source
Journal of Climate, 2021,
34 (22), 9025-9042 ISSN 0894-8755
We analyze the characteristics of atmospheric variations over tropical South America using the pattern recognition framework of weather typing or atmospheric circulation patterns (CPs). During 1979-2020, nine CPs are defined in the region, using a k-means algorithm based on daily unfiltered 850-hPa winds over 10 degrees N-30 degrees S, 90 degrees-30 degrees W. CPs are primarily interpreted as stages of the annual cycle of the low-level circulation. We identified three "winter' CPs (CP7, CP8, and CP9), three "summer' CPs (CP3, CP4, and CP5), and three "transitional' CPs (CP1, CP2, and CP6). Significant long-term changes are detected during the dry-to-wet transition season (July-October) over southern tropical South America (STSA). One of the wintertime patterns (CP9) increases from 20% in the 1980s to 35% in the last decade while the "transitional' CP2 decreases from 13% to 7%. CP9 is characterized by enhancement of the South American low-level jet and increasing atmospheric subsidence over STSA. CP2 is characterized by southerly cold-air incursions and anomalous convective activity over STSA. The years characterized by high frequency of CP9 and low frequency of CP2 during the dry-to-wet transition season are associated with a delayed South American monsoon onset and anomalous dry conditions over STSA. Consistently, a higher frequency of CP9 intensifies the fire season over STSA (1999-2020). Over the Brazilian states of Maranhao, Tocantins, Goias, and Sao Paulo, the seasonal frequency of CP9 explains around 35%-44% of the interannual variations of fire counts.
Plan de classement
Sciences du milieu [021]
;
Bioclimatologie [072]
Description Géographique
BRESIL ; AMAZONIE ; ZONE TROPICALE
Localisation
Fonds IRD [F B010084281]
Identifiant IRD
fdi:010084281
