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-15 -20 -25 -30 -35 -40 -15 -20 -25 -30 -35 Regional precipitation trends A B -40 C D -70 -65 -60 -55 -50 -45 -40 -70 -65 -60 -55 -50 -45 -40 Fig. 5.5. Precipitation trends for 1961-2000 in mm/yr. (a) annual precipitation, (b) La Niña contribution, (c) El Niño contribution, and (d) Neutral years contribution. The positive trend is in the band between 20° and 40°S East of the Andes Mountains. El Niño contribution to the trend is noticeable for the region that goes from Paraguay, through Northeaster Argentina up to Rio Grande in Brazil. To the South, El Niño contribution to the trend is close to zero, while the Neutral years appear to be the ones that carry most of the trend signal. Neutral years also contribute to the maximum in the region of the triple boundary of Paraguay, Brazil and Argentina. It can also be noticed that during La Niña periods the trend is close to zero everywhere. In other words, largest contributions to precipitation trends are found during El Niño or Neutral years, but not during La Niña years. These results are relevant when preparing future scenarios of climate change, because they provide important information about the mechanisms behind the trends observed in the last few decades. 67
Regional precipitation trends 5.3.2. Frequency of extreme precipitation Frequency of heavy precipitations in Argentina has increased notably since the late 1970s (Fig. 5.6). Since that time, the number of recorded cases with precipitations over 100 mm in less than 48 hours has been three folded in the Centre and East of Argentina and the same happens with the thresholds of 50 and 1590 mm (Barros 2004). Fig. 5.6. Number of cases with precipitation larger than 100 mm. It should be noted that cases as those documented in figure 5.6 are the ones that lead to floods, particularly if the terrain favours surface runoff that concentrates the water in certain areas Increased frequency of extreme rainfalls has been observed also in southern Brazil (Xavier et al. 1992 y 1994), especially in summertime. This seems part of a global trend, which on the other hand should be expected because of the increased concentration of the greenhouse gasses. This increment would lead to the warming of the low level troposphere favouring larger water vapour content and a vertical gradient more unstable as a consequence of the stratospheric cooling. Both changes, more vertical instability and greater water vapour content favours the development of the intense rainfall processes 68
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CLIMATE CHANGE IN THE LA PLATA BASI
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INDEX FOREWORD . . . . . . . . . .
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7.3. Methodology . . . . . . . . .
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13.3. Regional validation of GCM fo
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1.1. Dropping the hypothesis of sta
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Introduction as they pour water ove
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A better understanding of the obser
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References Introduction Barros, V.
Page 17 and 18: ABSTRACT The hydrologic cycle of th
Page 19 and 20: La Plata basin climatology Within t
Page 21 and 22: in this last description, although
Page 23 and 24: warm season (October-April), in the
Page 25 and 26: La Plata basin climatology b. Upper
Page 27 and 28: La Plata basin climatology 2.3.3. R
Page 29 and 30: La Plata basin climatology Fig. 2.8
Page 31 and 32: 2.3.7. West and South borders La Pl
Page 33 and 34: References La Plata basin climatolo
Page 35 and 36: La Plata basin climatology Robertso
Page 37 and 38: 3.1. Introduction Interannual low f
Page 39 and 40: Interannual low frequency variabili
Page 41 and 42: 1989). This signal varies along eac
Page 43 and 44: Interannual low frequency variabili
Page 45 and 46: The main physiographic and hydrolog
Page 47 and 48: SUB-BASIN COUNTRY Argentina Bolivia
Page 49 and 50: the most important stretches of the
Page 51 and 52: Physiography and Hydrology The Para
Page 53 and 54: Physiography and Hydrology The Pant
Page 55 and 56: Physiography and Hydrology forcings
Page 57 and 58: Physiography and Hydrology It is no
Page 59 and 60: Physiography and Hydrology tion of
Page 61 and 62: Physiography and Hydrology INTERNAV
Page 63 and 64: 5.1. Introduction Precipitation and
Page 65 and 66: From 1956 to 1991, in most of the A
Page 67: -15 -20 -25 -30 -35 -40 -15 -20 -25
Page 71 and 72: Regional precipitation trends and L
Page 73 and 74: trast, other regions suffer floodin
Page 75 and 76: ABSTRACT The main hydrological tren
Page 77 and 78: Following are the observed changes:
Page 79 and 80: In the case of the Paraná River th
Page 81 and 82: Hydrological trends In order to com
Page 83 and 84: Hydrological trends In table 6.1 it
Page 85 and 86: Hydrological trends On the other ha
Page 87 and 88: the central area of the high basin
Page 89 and 90: 7.1. Introduction Several authors,
Page 91 and 92: Real evaporation trends a) PET > Pi
Page 93 and 94: a) b) c) Mean Temperature Real evap
Page 97 and 98: The positive trends of the mean tem
Page 99 and 100: d) e) f) Mean Temperature Real evap
Page 103 and 104: 7.5. Discussion and final comments
Page 105 and 106: ABSTRACT The water, as resource, is
Page 107 and 108: puts in risk large number of person
Page 109 and 110: The main services and problems of w
Page 111 and 112: There are similar problems in diffe
Page 113 and 114: 8.3.3. Energy a. Hydroelectric depe
Page 115 and 116: (chapters 12 and 13), because of th
Page 117 and 118: The main services and problems of w
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9.1. Introduction The emissions of
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9.4. Greenhouse effect The atmosphe
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Temperature anomalies (°C) 0.8 0.6
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Global climatic change at a global
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In view of the unavoidability of th
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Background on other regional aspect
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Considering the non-linear interact
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SST anomalies also have influence o
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ABSTRACT The purpose of this chapte
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Global climate models Mid-1970’s
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Global climate models Table 11.1. B
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Global climate models Table 11.2. M
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Although changes in weather and cli
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Socio-economic variables and also s
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Applicability in impact assessments
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of the global climate system to the
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Climate scenarios B2: Assumes a wor
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Climate scenarios The reliability o
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Climate scenarios From Table 12.2 i
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Climate scenarios Fig. 12.5. The mu
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Climate scenarios this would be rel
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Results of global circulation model
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13.2.3. Statistical downscaling The
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La Plata basin are also considerabl
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10 N EQ 10 S 20 S 30 S 40 S 50 S 10
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Regional climatic scenarios Fig. 13
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a. Pre-industrial experiment: Initi
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Regional climatic scenarios Kalnay,
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Low-frequency variability 14.1. Bac
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egime occurred during the periods o
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Fig. 14.2. As Fig. 14.1, except for
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14.4. SST composites Low-frequency
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Low-frequency variability during th
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Fig. 14.10. As Fig. 14.9, except fo
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Low-frequency variability In genera
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Low-frequency variability Mantua, N
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15.1. Introduction Statistical anal
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Statistical analysis of extreme eve
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CURRÍCULA OF THE AUTHORS Vicente B
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Curricula of the autors Rubén Mari
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Proyect: SGP II 057: “Trends in t
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