Intraseasonal variability of summer convection over South America
Hirata, Fernando E.
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In other regions of the world, intraseasonal variations of precipitation have been used to extend the range of weather and hydrological forecasts especially during the rainy monsoon season. This intraseasonal variability is usually strongly tied to the Madden Julian Oscillation (MJO). First, the focus is on variations of the MJO as it propagates eastward. Three main categories are described. One is the canonical MJO, which propagates almost continuously from the Indian Ocean to the West Pacific. The other categories encompass intraseasonal convection that fails to reach the West Pacific and intraseasonal convection that begins closer to the Maritime Continent and intensifies while propagating eastward. The categories of intraseasonal convection are linked to intraseasonal variations of South American rainfall and it is demonstrated that the SACZ is influenced by the MJO both through the tropics and extratropics. There is evidence that accumulation of wave energy is an important process both to organize extratropical waves propagating from the Pacific to South America and to promote convection in the South Atlantic Convergence Zone (SACZ). In the long-term, variations of the SACZ are related to climate regimes in the Pacific Ocean, highlighting the fact that there is a shift of spectral energy in SACZ convection from intraseasonal to higher frequencies, indicating again the importance of extratropical waves for SACZ convection. Last, the main findings of this project are discussed, as well as their applicability to enhance precipitation predictability over South America.