Connecting heavy precipitation events to outgoing longwave radiation variability scales: case analysis in Brazil

MÜLLER, GABRIELA. V.; FERNANDES, VALESCA

Atmósfera

Universidad Nacional Autónoma de Mexico (UNAM)

Año: 2021 vol. 36 p. 77 - 90

2395-8812

Spatial fields of outgoing longwave radiation (OLR) spectrum variance of the 1979-201626 austral summer months in southern Brazil are analyzed on different time-scales: synoptic, sub27 monthly, and intra-seasonal. Variability fields differ both in intensity and location and highlight28 dominant convection cycles in the study area. The results show that the amplitude of sub29 monthly variability is greater than that of the other scales in the southeastern region of Brazil,30 while the synoptic scale prevails in the southern region. The above-mentioned scales show31 greater amplitudes over the western Pacific Ocean where the Madden-Julian Oscillation plays32 an important role, along the South Pacific Convergence Zone, and over the storm track areas33 over the South Pacific Ocean. The influence of spectral OLR scale interaction is also analyzed,34 associated to the occurrence of two intense rainfall events over the southeastern Brazil in the35 austral summers of 2011 and 2014 when the South Atlantic Convergence Zone was active in36 both events. The results obtained suggest that spectral OLR scale interaction takes place in such37 way that it strengthens the South Atlantic Convergence Zone, since the spatial pattern footprints38 of the 2 to 8-day timescale (synoptic), 10 to 30-day timescale (sub-monthly) and 30 to 60-day39 timescale (intra-seasonal) overlap in the study region.