1. THE SACZ PERSISTENCE, FORM INTENSITY, INTRASEASONAL TO INTERANNUAL VARIATIONS AND IMPACTS ON EXTREME PRECIPITATION EVENTS
Leila M. V. Carvalho1,2 1IAG, University of São Paulo, Brazil Charles Jones 2ICESS- University of California, Santa Barbara Brant Liebmann NOAA-CIRES, Climate Diagnostic Center, Boulder, CO

2. The South Atlantic Convergence Zone (SACZ)
OLR standard deviation

3. OBJETIVES:
Objectively identify the SACZ INTENSITY, PERSISTENCE AND FORM (OCEANIC vs CONTINENTAL) using daily OLR data.
Investigate the relationships between intraseasonal variations (10-90 days) and the SACZ spatial and temporal characteristics.
Discuss the implication of the SACZ characteristics to the occurrence of daily extreme precipitation over Brazil.
Examine the role of the MJO activity in modulating the SACZ persistence.
Investigate the SACZ interannual variations, relationships with ENSO phases and implications to daily extreme precipitation over Brazil.

4. * Determination of the SACZ Characteristics
METHODOLOGY
* Determination of the SACZ Characteristics
Contiguous regions of OLR  200W m-2 are identified in daily data (OLR200) (DJF 1979/ /2000)
Three regions are defined to search for patterns of convective activity: AMAZON, COASTAL and OCEAN. All selected OLR200 intercepted the COASTAL area.
FACTOR ANALYSIS for discrimination of events according to the intensity (weak or intense) and form (oceanic or continental) of deep convection in the SACZ. Input  SPATIAL PROPERTIES OF OLR200.
*Carvalho, LMV, C. Jones and B. Liebmann, 2002: Extreme precipitation events in southeastern South America and large-scale convective patterns in the South Atlantic Convergence Zone, J. Climate,

5. EXAMPLE OF OLR200 PROPERTIES
Eccentricity:
Minor axis/major axis
• Total Area
• Internal Variance
• Minimum OLR
• Fraction of Min OLR
Fraction AMAZON
Fraction COASTAL
Fraction OCEAN
EXAMPLE OF OLR200 PROPERTIES
MASCOTTE Algorithm:
Carvalho and Jones (2001):
J. Appl. Meteor

6. Intensity Form INTENSE : Fact 1 <0 CONTINENTAL: Fact 2>0 Fact-1
N=1750 (DJF)
Variable
Fact-1
Fact-2
AREA
-.82
.03
Ecc
.01
.77
OLRmin
.89
-.06
%OLRmin
.87
-.01
VarOLR
-.70
.04
% Coastal
.82
.07
% Amazon
-.57
.42
% Ocean
.00
-.83
Eigenvalues
3.73
1.48
%Variance 47 19
WEAK :
Fact 1 >0
OCEANIC:
Fact 2<0

7. SACZ AND INTRASEASONAL ACTIVITY
SACZ CATEGORIES
INTENSE : Factor-1  25th quartile
WEAK : Factor-1  75th quartile
OCEANIC : Factor-2  25th quartile
CONTINENTAL : Factor-1  75th quartile
PERSISTENCE: sequence of days in a given category
SACZ AND INTRASEASONAL ACTIVITY
composites of OLR, low-level (850hPa) winds and geopotential height (200hPa) from filtered data (10-90 days).
MJO ACTIVITY
EOF analysis of OLR anomalies (10-90 days) (DJF)
Selection of events PC1 (PC2)  1 ( -1) DJF standard deviation

8. OLR Daily Anomalies (W m-2) Intense SACZ
OLR Daily Anomalies (W m-2) Weak SACZ
OLR Daily Anomalies (W m-2) Oceanic SACZ
OLR Daily Anomalies (W m-2) Continental SACZ
Figure 3

9. SACZ Composites 10-90 days anomalies
westerlies
easterlies

10. Carvalho, L. M. V. , C. Jones, and M. A. F
Carvalho, L. M. V., C. Jones, and M. A. F. Silva Dias, 2002: Intraseasonal large-scale circulations and mesoscale convective activity in Tropical South America during the TRMM-LBA campaign. J. Geoph. Res. (in Press).
Jones, C. , and L. M. V. Carvalho, 2002: Active and break phases in the South American Monsoon System. J. Climate, 15,

12. TIME-INTERVAL BETWEEN PERSISTENT EVENTS
Outliers : data point values  1.5 times the interquartile range.
Extremes: data point values  3.0 times the interquartile range.

15. Extracted from CPC achieves
INTERANNUAL VARIABILITY
Extracted from CPC achieves

16. MJO ACTIVITY

17. THE MJO ACTIVITY AND SACZ PERSISTENT CATEGORIES

18. Frequency  5% (in green). Frequency  15% (yellow)
Frequency of extremes : SACZ Intense
Frequency of extremes : SACZ Weak
Frequency  5%
(in green). Frequency
 15% (yellow)
DJF 95th percentile (mm/day)
Frequency of extremes : SACZ Oceanic
Frequency of extremes: SACZ Continental

19. PC2 <0
PC2>0
PC1 <0
PC1>0

21. CONCLUSIONS: SACZ and intraseasonal variations
The proposed methodology objectively characterizes the SACZ intensity and spatial properties.
There is evidence of a mid-latitude wave train modulating continental/oceanic SACZ categories
Persistence of SACZ categories have similar distribution.
The median time interval between persistent categories is similar and equal to 6 days, although more variability is observed for intense SACZ.
The ratio frequency of intense/weak SACZ with persistence ≥ 3 days increases during La Nina years, the opposite occurring during El Nino and Neutral years.
The spatial distribution of extreme precipitation events (≥ 95th percentile) varies with SACZ categories
MJO occurrences seem to modulate intense SACZ persistence 
MJO have an important role for the occurrence of extreme precipitation over central-east and northeast Brazil. Importance of monitoring MJO activity to improve rainfall predictability in the South America Monsoon System.