Tuesday, 9 January 2018
Exhibit Hall 3 (ACC) (Austin, Texas)
This study analyzes the influence of Madden-Julian oscillation (MJO) on intraseasonal rainfall variability over the Amazon basin (AB) using gauge-based grid rainfall data estimated from 752 meteorological stations for the 1980-2009 period. The Principal Component (PC1) time series from the intraseasonal rainfall data are used to select intraseasonal rainfall events (IE). A total of 132 IE were identified in an average of ~5 events per year. In addition, we find the incomplete intraseasonal events (events with incomplete life cycle), which create synoptic conditions for suppressed rainfall over tropical South America. The frequency of IE below (above) the average were recorded during El Niño Southern Oscillation (ENSO) warm (cold) years. Moreover, incomplete intraseasonal events show strong activity during ENSO warm years and during the severe drought of 2005. The development of IE over tropical South America, for all seasons, compared with different phases of the MJO index, shows a coherent relationship. Rainfall composites based on the PC1 time-series show that the MJO is the main atmospheric-mechanism modulator of the intraseasonal rainfall variations over the Amazon region for all seasons. This modulation is particularly important during the dry season, when the percentage of the contribution of MJO related to the positive rainfall anomaly is greater than 70%.
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