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首页> 外文期刊>Climate dynamics >Observed precipitation in the Parana-Plata hydrological basin: long-term trends, extreme conditions and ENSO teleconnections
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Observed precipitation in the Parana-Plata hydrological basin: long-term trends, extreme conditions and ENSO teleconnections

机译：巴拉那-普拉塔水文盆地的观测降水：长期趋势，极端条件和ENSO遥相关

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The Parana-Plata basin is the second largest hydrological basin in South America and is of great importance for the countries of the region (Argentina, Bolivia, Brazil, Paraguay and Uruguay). The present study focuses on the long-term trends in basin-scale precipitation with special emphasis on the role of distribution changes in extreme large-scale precipitation events and on the characteristics and evolution of ENSO teleconnections over the last 50 years. First, we defined a Parana-Plata basin total precipitation index ( PTPI) as the precipitations spatially averaged over the hydrological basin. On interannual time scales, such an index is mainly representative of anomalous monsoon precipitations in the northern part of the basin and large convective precipitation anomalies in the center of the basin (Paraguay-southern Brazil-Uruguay-northern Argentina) typical of the canonical ENSO teleconnection pattern. Our major findings clearly highlight a positive trend in yearly averaged PTPI mainly from the late 1960s to the early 1980s with a strong dependence from month-to-month. The largest precipitation increase is observed from November to May in southern Brazil and Argentina. A close examination of PTPI distributions during the two halves of the period 1950-2001 shows that the changes in the mean state from 1950-1975 to 1976-2001 result from significant changes in each calendar month mean state and in the tails of the PTPI anomaly distributions in May with lesser and weaker large-scale dry events and stronger large-scale wet events. Further studies will be needed to assess whether the observed trend in large-scale extreme precipitation conditions can be related to natural climate variability or anthropogenic activities and whether it is associated to changes in local/regional extreme events. The stronger wet conditions in different months seem to be associated to changes in ENSO characteristics ( amplitude, propagation, spatial structure, ...) since the 1982-1983 El Nino. Indeed, spatial ENSO teleconnections ( stronger in November and April-May) have greatly evolved from 1950-1975 to 1976-2001. Moreover, we demonstrate that there is a strong modulation and displacement of the teleconnection patterns from one event to another, impeding the definition of robust statistical relationship between ENSO and precipitation in the Parana-Plata basin (except maybe over a very limited area near the common border between Paraguay, Argentina and Brazil). Finally, the non-antisymmetrical patterns of precipitation between El Nino and La Nina conditions and the non-linear relationship between precipitation and either Nino3.4 or Nino1+2 sea surface temperature indices show that linear statistical forecast systems are actually of very limited use for impact predictions on society on a local or regional scale.
机译：巴拉那-普拉塔盆地是南美第二大水文盆地，对于该地区的国家（阿根廷，玻利维亚，巴西，巴拉圭和乌拉圭）具有重要意义。本研究着重于流域尺度降水的长期趋势，特别强调了分布变化在极端大规模降水事件中的作用以及过去50年ENSO遥相关的特征和演变。首先，我们将巴拉那-普拉塔盆地的总降水指数（PTPI）定义为水文盆地的空间平均降水量。在年际尺度上，该指数主要代表盆地北部的季风降水异常和盆地中心（巴拉圭-巴西南部-巴西乌拉圭-阿根廷北部）的典型对流降水异常。图案。我们的主要发现清楚地表明，主要是从1960年代末到1980年代初，每年平均PTPI呈积极趋势，并且每个月都有很大的依赖性。在巴西南部和阿根廷，从11月至5月观测到最大的降水增加。仔细检查1950-2001年期间的两半期间的PTPI分布，可以发现1950-1975年至1976-2001年的平均状态变化是由于每个日历月的平均状态和PTPI异常尾部的显着变化导致的5月的分布比较少，大型旱灾事件减弱，而大型旱灾事件减弱。需要进行进一步的研究，以评估在大规模极端降水条件下观测到的趋势是否与自然气候变异或人为活动有关，以及是否与当地/区域极端事件的变化有关。自1982年至1983年厄尔尼诺现象以来，不同月份的强湿条件似乎与ENSO特征（振幅，传播，空间结构等）的变化有关。实际上，从1950-1975年到1976-2001年，空间ENSO遥相关（11月和4月-5月增强）。此外，我们证明遥距连接模式从一个事件到另一个事件之间有很强的调制和位移，这妨碍了巴拉那-普拉塔盆地ENSO与降水之间稳健的统计关系的定义（除非可能在共同点附近非常有限的区域内）巴拉圭，阿根廷和巴西之间的边界）。最后，厄尔尼诺和拉尼娜条件之间的降水非对称模式以及降水与Nino3.4或Nino1 + 2海表温度指数之间的非线性关系表明，线性统计预报系统实际上在以下方面的应用非常有限在地方或区域范围内对社会的影响预测。

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