The joint impacts of Atlantic and Pacific multidecadal variability on South American precipitation and temperature
The joint impacts of Atlantic and Pacific multidecadal variability on South American precipitation and temperature
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DOI：
10.1175/jcli-d-21-0081.1
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发表时间：
2021-07
影响因子：
4.9
通讯作者：
Zhaoxiangrui He;A. Dai;M. Vuille
中科院分区：
文献类型：
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作者：
Zhaoxiangrui He;A. Dai;M. Vuille
南美洲气候受大西洋十年变率(AMV)和太平洋十年变率(PMV)的影响。但它们是如何共同影响南美降水和地表气温的，目前还不清楚。在这里，我们使用观测和再分析数据来分析复合异常，以量化它们的综合影响。在AMV暖(冷)阶段，PMV诱发的JJA降水异常在0°-10°S和南美洲东南部偏正(负)，而在亚马逊北部和巴西中部偏负(正)。在暖(冷)AMV阶段，DJF由PMV引起的降水异常在巴西东北部和南美洲东南部较正(负)，而在亚马孙盆地中部和巴西中东部则较负(正)。PMV对AMV诱发的降水异常的影响表现出类似的偶极子模式。降水变化是局地Hadley环流和Walker环流扰动的结果。在JJA，当另一个盆地处于暖(冷)相时，PMV和AMV引起的温度异常在整个南美洲都是较正(负)的，而在DJF，温度异常仅在安第斯山脉中部和巴西中东部地区较正(负)，而在南美洲东南部和巴塔哥尼亚则较负(正)。在JJA的巴西中部和DJF的玻利维亚南部和阿根廷北部，温度和降水异常呈负相关。我们的结果表明，太平洋和大西洋年代际变化的影响需要联合考虑，因为在另一个海盆的模式的冷相或暖相期间，可能会发生与平均AMV或PMV指纹显著偏离的情况。
South American climate is influenced by both Atlantic multidecadal variability (AMV) and Pacific multidecadal variability (PMV). But how they jointly affect South American precipitation and surface air temperature is not well understood. Here we analyze composite anomalies to quantify their combined impacts using observations and reanalysis data. During an AMV warm (cold) phase, PMV-induced JJA precipitation anomalies are more positive (negative) over 0°-10°S and southeastern South America, but more negative (positive) over the northern Amazon and central Brazil. PMV-induced precipitation anomalies in DJF are more positive (negative) over Northeast Brazil and southeastern South America during the warm (cold) AMV phase, but more negative (positive) over the central Amazon Basin and central-eastern Brazil. PMV’s impact on AMV-induced precipitation anomalies shows similar dipole patterns. The precipitation changes result from perturbations of the local Hadley and Walker Circulations. In JJA, PMV- and AMV-induced temperature anomalies are more positive (negative) over entire South America when the other basin is in a warm (cold) phase, but in DJF temperature anomalies are more positive (negative) only over the central Andes and central-eastern Brazil and more negative (positive) over southeastern South America and Patagonia. Over central Brazil in JJA and southern Bolivia and northern Argentina in DJF, the temperature and precipitation anomalies are negatively correlated. Our results show that the influence of Pacific and Atlantic multidecadal variability need to be considered jointly, as significant departures from the mean AMV or PMV fingerprint can occur during a cold or warm phase of the other basin’s mode.