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Recent intensification of extreme precipitation events in the La Plata Basin in Southern South America (1981–2018)
Atmospheric Research ( IF 5.5 ) Pub Date : 2021-02-01 , DOI: 10.1016/j.atmosres.2020.105299
Wilmar L. Cerón , Mary T. Kayano , Rita V. Andreoli , Alvaro Avila-Diaz , Irma Ayes , Edmilson D. Freitas , Jorge A. Martins , Rodrigo A.F. Souza

Abstract Changes and trends in ten extreme daily rainfall indices in the La Plata Basin (LPB) during the 1981–2018 period were analyzed. These indices were evaluated for three regions in the LPB, namely the northern, central, and southern LPB (N-LPB, C-LPB, and S-LPB, respectively). A decrease in the maximum rainfall over five consecutive days (RX5day) and an increase in the consecutive dry days (CDD) were observed in N-LPB, mainly during the austral winter. An increase in the total wet-day precipitation was found in S-LPB, particularly during September–November (SON), and during December–February (DJF). The number of heavy precipitation days (R10mm) and CDD indices in S-LPB during SON showed a breaking point in 1999 and were followed by an increase in R10mm after 1999. Therefore, we discussed the large-scale climatic features that could be related to the breaking point in the extreme precipitation indices found in the S-LPB during SON, through correlation analysis. Our results indicate that R10mm shows significant positive correlations with the sea surface temperature (SST) in the Southwestern Subtropical Atlantic Region, mainly between 32°S–22°S and 50 W–34°W. The SST anomaly index in this oceanic region for SON during 1981–2018 displayed a significant upward change in 1999. Furthermore, the correlation map between this index and the vertically integrated moisture flux (VIMF) and its divergence, shows negative correlations in the S-LPB, which means a decrease of the moisture divergence in this region. This implies an increase (decrease) of R10mm, and a decrease (increase) of CDD in the S-LPB after (before) 1999. This relationship results from an anticyclone in the Southwestern Atlantic extending into the LPB up to 60°W, which causes an increase in the northwesterly moisture flux over central and southern parts of the basin, enhancing the moisture convergence over S-LPB. These insights have not been discussed previously, and might be relevant for future modeling studies and monitoring tasks.

中文翻译:

南美洲南部拉普拉塔盆地极端降水事件的近期加剧(1981-2018)

摘要 分析了拉普拉塔盆地(LPB)1981-2018年10个极端日降雨指数的变化趋势。这些指数针对 LPB 中的三个区域进行评估,即北部、中部和南部 LPB(分别为 N-LPB、C-LPB 和 S-LPB)。在 N-LPB 中观察到连续五天 (RX5day) 的最大降雨量减少和连续干旱天数 (CDD) 增加,主要是在南方冬季。在 S-LPB 中发现总湿日降水量增加,特别是在 9 月至 11 月 (SON) 和 12 月至 2 月 (DJF)。SON 期间 S-LPB 的强降水日数 (R10mm) 和 CDD 指数在 1999 年出现突破点,1999 年之后 R10mm 增加。因此,我们通过相关分析讨论了可能与 SON 期间在 S-LPB 中发现的极端降水指数的断点相关的大尺度气候特征。我们的结果表明,R10mm 与西南亚热带大西洋地区的海面温度(SST)呈显着正相关,主要在 32°S–22°S 和 50 W–34°W 之间。1981-2018 年该洋区 SON 海温异常指数在 1999 年呈现显着上升变化。此外,该指数与垂直积分水汽通量(VIMF)及其散度的相关图显示,S- LPB,这意味着该区域的水分差异减少。这意味着 1999 年之后(之前)S-LPB 中 R10mm 的增加(减少)和 CDD 的减少(增加)。这种关系是由于西南大西洋的反气旋延伸到 LPB 高达 60°W,导致盆地中部和南部的西北湿气通量增加,增强了 S-LPB 上的湿气辐合。这些见解以前没有讨论过,可能与未来的建模研究和监测任务相关。
更新日期:2021-02-01
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