Monthly precipitation samples from Singapore were collected between 2013 and 2019 for stable isotope analysis to further our understanding of the drivers of tropical precipitation isotopes, in particular, ¹⁷O‐excess. δ¹⁸O ranges from –11.34‰ to –2.34‰, with a low correlation to rainfall (r = –0.31, p = 0.014), suggesting a weak amount effect. d‐excess is relatively consistent and has an average value of 10.89‰ ± 3.45‰. Compared to high‐latitude regions, ¹⁷O‐excess in our samples generally falls in a narrower range from 2 to 47 per meg with an average of 21 ± 11 per meg. Moreover, ¹⁷O‐excess shows strong periodic variability; spectral analysis reveals 3‐month, 6‐month, and 2.7‐year periodicities, likely corresponding to intraseasonal oscillations, monsoons, and the El Niño–Southern Oscillation (ENSO), respectively. In contrast, d‐excess shows no clear periodicities. Although spectral analysis only identifies 6‐month periodicity in the δ¹⁸O time series, δ¹⁸O tracks the Nino3.4 sea surface temperature variability; the average δ¹⁸O value (–5.2‰) is higher during El Niño years than ENSO neutral years (–7.6‰). Therefore, regional convection associated with monsoons and ENSO has different impacts on δ¹⁸O, d‐excess, and ¹⁷O‐excess. ¹⁷O‐excess and d‐excess are anticorrelated and do not relate to the relative humidity in moisture source regions. Extremely low humidity and drought conditions in moisture source regions would be required to account for high ¹⁷O‐excess. Processes during transport and precipitation likely modify these two parameters, especially ¹⁷O‐excess, which no longer record humidity conditions of moisture source regions. Our findings will be useful for further modeling studies to identify physical processes during convection that alter d‐excess and ¹⁷O‐excess.

中文翻译：

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通过海洋大陆的三重氧同位素了解热带对流

2013年至2019年之间，新加坡收集了每月的降水样本，以进行稳定的同位素分析，以进一步了解热带降水同位素的驱动因素，尤其是¹⁷ O过量。δ ^18米从-11.34‰至-2.34 O范围‰，具有低相关性，以降雨量（[R  = -0.31，p  = 0.014），表明弱量的效果。d-过量相对一致，平均值为10.89‰±3.45‰。与高纬度地区相比，我们样本中的¹⁷ O过量通常在每兆2到47的较窄范围内，平均每兆21±11。而且¹⁷O过量显示强烈的周期性变化；频谱分析显示3个月，6个月和2.7年的周期，可能分别对应于季节内振荡，季风和厄尔尼诺-南方涛动（ENSO）。相比之下，d过量没有明确的周期性。虽然频谱分析只标识了δ6个月的周期¹⁸ O时间系列，δ ^18个ö轨道Nino3.4海面温度变化; 平均δ ¹⁸ O值（-5.2‰）在厄尔尼诺年比ENSO中性年（-7.6‰）较高。因此，区域对流与季风相关联，并且ENSO对δ不同的影响¹⁸ O，d-过量，和¹⁷ O型过量。¹⁷过量和过量是反相关的，与湿度源区域的相对湿度无关。需在湿度源区域中极低的湿度和干旱条件才能解决¹⁷ O过量的问题。运输和降水过程中的过程可能会修改这两个参数，尤其是¹⁷ O-过量，不再记录湿气源区域的湿度条件。我们的发现将有助于进一步的建模研究，以识别对流过程中改变d过量和¹⁷ O过量的物理过程。