An Observed Trend of Precipitation in the PROSUR Area of South America Brant Liebmann Carolina S. Vera Leila M.V. Carvalho Ines Camilloni Marty P. Hoerling.

Apresentação em tema: "An Observed Trend of Precipitation in the PROSUR Area of South America Brant Liebmann Carolina S. Vera Leila M.V. Carvalho Ines Camilloni Marty P. Hoerling."— Transcrição da apresentação:

1 An Observed Trend of Precipitation in the PROSUR Area of South America Brant Liebmann Carolina S. Vera Leila M.V. Carvalho Ines Camilloni Marty P. Hoerling Dave Allured Tendencia de precipitacão observada na area PROSUR da America do Sul

2 Se um evento de inundacão esta definido como dois desvios- padrão da anomalia mensal do fluxo em Corrientes, Argentina, então existem quase seis vezes mais inundacões nos 20 anos entre 1980-1999 que existiram nos 60 anos entre 1920-1979.

3 Previous work: Barros, Castaneda, Doyle (2000): Increase in precipitation over most of Argentina from 1956-1991. Decrease in meridional temperature gradient. Castaneda and Barros (1994): Humid Pampa increase in rain, mainly after 1960. Vargas (1987): Grimm: Marengo:

4 Data We wish to thank the following agencies for providing the data used in this study: Agência Nacional de Águas (Brasil) Agência Nacional Energia Elétrica (Brasil) U.T.E. Uruguay C.T.M. Salto Grande Servicio Meteorologico Nacional (Argentina, Paraguay, Uruguay) FUNCEME (Ceará, Brasil) SIMEPAR (Paraná, Brasil) DAEE (São Paulo, Brasil) Minesterio del Ambiente y los Recursos Naturales (Venezuela) Meteorogische Dienst Suriname METEO-France

5 1976-1999 Climatology January-March TotalDecember-February Total

6 Index:47W-53W 23S-29S “southern Brasil”

7 JFM climo 1976-1981JFM climo 1994-1999

8 JFM climo difference – 1994/99 minus 1976/81

9 What are the characteristics of the observed trend? Quais são as caracteristicas da tendencia observada?

10 Slope = 3.87 mm/yr Slope = 3.16 mm/yr Slope = 0.165 mm/yr Slope = -1.2 mm/yr

11 A(dia) = Acumulación anómala R(n) = lluvia diaria R = promedio anual de precipitación diaria Se considera que la estación lluviosa tiene lugar cuando la pendiente de la curva es positiva ( R(n) > R ).

12 Fecha promedio de iniciación: 30 de diciembre Este Central de la Amazonia

13

14 Average onset date = 25 October 1 January

15 Average onset date = 25 OctoberAverage end date = 9 April 31 March

16 Average onset date = 25 OctoberAverage end date = 9 April

17 difference Rainy day average = 14.8 17.5 Percent dry days = 57.2 46.0 1976-1981 1994-1999

18 Is observed precipitation trend due to a change in synoptic variability? Esta tendencia é devido a mudanca na variabilidade sinotica?

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21 statistical significance of trend 95% 97.5% 99% Trend in JFM daily 700 mb heat flux (1976-1999) _ +

22 Is there a relationship between observed precipitation trend and sea surface temperature? Esta tendencia observada na precipitacão esta relacionada a temperatura da superficie do mar (TSM)?

23 Simultaneous Correlation

24 Available stations - 1980Available stations - 1948

25 Slope: 1976 - 1999 = 7.20 1948 - 1975 = 1.11 1948 - 1999 = 1.53

26

27 Slope (m3/s/yr): 1976-1999 = 49.2 1948-1075 = 20.2 1948-1999 = 17.2 Precipitation has increased by 35% (along trend line) River flow has increased by 161% (amplification and delay noted by Berbery and Barros (2002))

28 Slope: 1976 - 1999 = 0.045 deg/yr 1948 - 1975 = 0.022 1948 - 1999 = 0.022 Slope: 1976 - 1999 = 7.20 mm/yr 1948 - 1975 = 1.11 1948 - 1999 = 1.53 SST in southwest AtlanticJan-March rainfall Season rainfall (mm/yr) Jan-Mar SST (C)

29 95% ‘significant’ Using 2-sided t-test

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32 An observed positive precipitation trend during the rainy season in Southern Brazil is most prominent from 1976-1999, but is evident earlier. The trend is consistent with a change in river flow. The trend is characterized by an increase in the number of rainy days per season and an increase in the amount per rainy day. The precipitation trend is related to one in SST, although perhaps not causally. The SST trend seems to result from a decrease in the strength of the South Atlantic high.