Intraseasonal to interannual variability of extreme precipitation over southeastern South America du

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Intraseasonal to interannual variability of
extreme precipitation over southeastern South
America during the Austral Summer

• 1Michel N. Muza, 1 Leila M. V. Carvalho, 2Brant
  Liebmann
• 1 University of Sao Paulo
• 2 NOAA-CIRES Climate Diagnostics Center

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Questions

• 1.What are the relationships between extreme
  positive/negative precipitation anomalies on
  intraseasonal (IS) and interannual time-scales
  (IA) over southeastern South America?
• 2. What are the main atmospheric features related
  to extremes on these time-scales?

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DATA

• Global Precipitation Climate Project (GPCP)
  (merge between satellite estimates and gauges)
• Period DJF 1979/80 2001/02 (Pentads) (2.5 lat
  x lon)
• ANEEL/DAEE precipitation from stations over
  Brazil
• NCEP/NCAR reanalysis

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GPCP (1979-2002) DJF STANDARD DEVIATION (mm/day)
INTRASEASONAL (20-90 DAYS)
INTERANNUAL (gt370 DAYS)
SE
S
SA
5x5 grid points
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METHOD

• Data were filtered on two time-scales
• 20-90 days (intraseasonal)
• gt 370 days (interannual)
• The DJF anomaly distribution is computed for each
  grid point for the two time-scales
• Extreme wet anomalies
• More than 50 of the grid points in a region
  presents anomalies gt 75th percentile of the
  respective DJF anomaly distribution
• Extreme dry anomalies
• More than 50 of the grid points in a region
  presents anomalies lt 25th percentile of the
  respective DJF anomaly distribution

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GPCP vs ANEEL gridded (2.5x2.5) (pentad) (79-1998)
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(No Transcript)
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GLOBAL PRECIPITATION EXTREME INTERANNUAL ANOMALIES
SE BRAZIL
WET
DRY
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GLOBAL PRECIPITATION EXTREME INTERANNUAL ANOMALIES
S BRAZIL
WET
DRY
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GLOBAL PRECIPITATION EXTREME INTERANNUAL ANOMALIES
SUBTROPICAL ATLANTIC
WET
DRY
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SST ( gt370 days)
SE BRAZIL DRY
SE BRAZIL WET
SUBT. ATLANTIC WET
SUBT. ATLANTIC DRY
S BR, UR, NE AG WET
S BR, UR, NE AG DRY
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850hPa V anomalies (gt370 days)
WET SE BR
WET SUBT. ATL.
WET S. BR, UR.
DRY SE BR
DRY SUBT. ATL.
DRY S. BR, UR.
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Intraseasonal anomalies (20-90 days)
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Intraseasonal Precipitation Anomalies (20-90
Days) Lag 0
WET SE BR
DRY SE BR
33 Dry
27 Wet
DRY SUBT. ATL.
WET SUBT. ATL.
24 Wet
36 Dry
WET S. BR, UR.
WET S. BR, UR.
43 Wet
42 Dry
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conclusions

• Interannual extreme wet/dry events
• SE Brazil related to phases of the South
  Atlantic TSM dipole and are more frequent during
  Neutral/La Nina episodes
• Subtropical Atlantic clearly decoupled from SE
  extremes
• Southern Brazil/Uruguay modulated by ENSO
  phases.
• Intraseasonal extreme wet/dry events
• Less than 20 of extreme intraseasonal wet (dry)
  pentads in all regions were observed during
  extreme wet (dry) seasons.
• Wet and dry intraseasonal extreme anomalies
  occur, in general, in the same season (1-2
  events). Only persistent (more than 2 pentads)
  events seem to play a role on the interannual
  extreme anomalies
• Persistent intraseasonal events have long
  characteristic time scales.
• The region with extreme wet (dry) anomalies
  depends on the phase of the propagating wave
  train corresponding to westerly (easterly) U200
  anomalies

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Acknowledgements

• DATA FROM NOAA, CPC, CDC, ANEEL, DAEE,
• YOUR PATIENCE

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U200 hPa ANOMALIES (20-90 days)
DRY southeastern Brazil
WET southeastern Brazil
DRY subtropical Atlantic
WET subtropical Atlantic
DRY southern Brazil
WET southern Brazil
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Fraction () of extreme wet (dry) intraseasonal
anomalies observed during extreme wet (dry)
interannual anomalies
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H200 Anomalies (20-90 days) 25th percentiles
southeastern Brazil
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H200 Anomalies (20-90 days) 75th percentiles
southeastern Brazil
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H200 Anomalies (20-90 days) 75th percentiles
subtropical Atlantic
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H200 Anomalies (20-90 days) 25th percentiles
subtropical Atlantic
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H200 Anomalies (20-90 days) 75th percentiles
southern Brazil
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H200 Anomalies (20-90 days) 25th percentiles
southern Brazil
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850 hPa wind (20-90 days) 75th percentiles
southeastern Brazil
850 hPa wind (20-90 days) 25th percentiles
southeastern Brazil
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850 hPa wind(20-90 days) 75th percentiles
subtropical Atlantic
850 hPa wind (20-90 days) 25th percentiles
subtropical Atlantic
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850 hPa wind (20-90 days) 75th percentiles
southern Brazil
850 hPa wind (20-90 days) 25th percentiles
southern Brazil
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Intercomparisons Low frequency and ENso
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Intercomparisons Intraseasonal and ENSO
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Intercomparisons south Atlantic dipole
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Intercomparisons Low frequency and dipole
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Intercomparisons Intraseasonal and dipole