ABSTRACT This study investigated the spatial variation of isotopes in precipitation over Thailand in relation to geographic condition. Monthly data (2013–2015) of stable isotopes (δ2H and δ18O) in precipitation within the region 5°37′–20°27′N, 98°04′–105°31′E were analysed using the least squares regression method to determine the possible effects of latitude and longitude on δ18O and d-excess in precipitation. Results showed that the spatial variability of isotopes in precipitation is affected by both continental and amount effects and that the variation is slightly greater in terms of latitude than longitude. Latitude and longitude effects both exhibited negative and positive correlations. Negative correlation, whereby isotopic values decreased with increasing latitude, was found during the June–August and September–November periods. Conversely, a positive relationship appeared in the December–February and March–May seasons. These effects had opposite correlation owing to the various moisture sources and different precipitation patterns between seasons. Furthermore, weak correlation for both latitude and longitude effects was revealed during September–November because of the intraseasonal variation of the monsoon. Consequently, the isotopic composition of precipitation in Thailand is controlled not only by geography but also by moisture source and precipitation pattern.

中文翻译：

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地理对泰国降水稳定同位素组成的影响

摘要 本研究调查了与地理条件相关的泰国降水中同位素的空间变化。使用最小二乘回归方法分析了 5°37'-20°27'N、98°04'-105°31'E 区域降水中稳定同位素（δ2H 和 δ18O）的月度数据（2013-2015）确定纬度和经度对降水中 δ18O 和 d-excess 的可能影响。结果表明，降水同位素的空间变异受大陆效应和数量效应的影响，纬度的变化略大于经度。纬度和经度效应均表现出负相关和正相关。在 6 月至 8 月和 9 月至 11 月期间发现了负相关，即同位素值随着纬度的增加而降低。反过来，12 月至 2 月和 3 月至 5 月季节出现了正相关关系。由于不同的水分来源和不同季节之间的降水模式，这些影响具有相反的相关性。此外，由于季风的季节性变化，在 9 月至 11 月期间，纬度和经度效应的相关性较弱。因此，泰国降水的同位素组成不仅受地理控制，还受水分来源和降水模式的控制。由于季风的季节性变化，在 9 月至 11 月期间，纬度和经度效应的相关性较弱。因此，泰国降水的同位素组成不仅受地理控制，还受水分来源和降水模式的控制。由于季风的季节性变化，在 9 月至 11 月期间，纬度和经度效应的相关性较弱。因此，泰国降水的同位素组成不仅受地理控制，还受水分来源和降水模式的控制。