The stable isotopes of oxygen and hydrogen in precipitation are widely used to track processes occurring within the hydrological cycle and understand regional atmospheric patterns that influence a specific area. Moreover, the oxygen isotopic composition of continental carbonates is extensively used for palaeohydrological reconstruction. Nevertheless, few comprehensive investigations have been performed in the Western Mediterranean to analyze the statistical relationships between oxygen and hydrogen stable isotopes in precipitation and meteorological variables. For understanding the factors that regulate the rainfall stable isotopic signature at present day in this area of Mediterranean region we selected the Tuscany region (central Italy), due to its considerable climatic seasonality, complex morphology and orography. Tuscany is affected by both Atlantic atmospheric disturbances from NW and moist air masses originated in the Mediterranean, and also by the secondary cyclogenesis center of the Gulf of Genoa, the most active in the entire Mediterranean. The ideal position of the Tuscany region thus offers the opportunity to investigate the complex influence of moisture sources on the rainfall isotopic composition. Moreover, in this region many hydrogeological and palaeohydrological studies were performed and require a more precise and quantitative interpretation.

In this work, 644 isotope monthly data (δ¹⁸O, δ²H, and deuterium excess) of precipitation collected in 12 sites through Tuscany from 1971 to 2018 were gathered in a database. Then, only sites whose monthly data covered almost one year were considered for processing, resulting in 553 precipitation samples archived along with monthly mean temperature and rainfall amount. In this framework, the LMWL for Tuscany was determined by applying different regression techniques and statistical analyses were performed to define the influence of meteorological and geographical variables on the rainfall isotopic composition. The outcomes point out the variations of rainfall isotopic signature as result of several climate and geographical variables than a univocal proxy for both local temperature and precipitation amount. The Atlantic and Mediterranean moisture sources differently contribute for generating the observed isotopic variability, and their influence may seasonally change. Overall, the temperature and amount effect allow to explain the 50% of the isotopic variability, but temperature appears to be more important. These local effects are more pronounced during the periods with low rainfall (spring and summer), whereas the large-scale processes (moisture origin, trajectories, and rainout) are prevailing in winter and autumn. The altitude effect is the main driver of isotopic spatial variability. The deuterium excess parameter is revealed to be a very complex but useful signal for disentangling the different contribution of Atlantic and Mediterranean sources in Tuscan precipitation, even if it is sometime misused.

降水中氧和氢的稳定同位素被广泛用于跟踪水循环中发生的过程，并了解影响特定区域的区域大气模式。此外，大陆碳酸盐岩的氧同位素组成被广泛用于古水文重建。然而，在西地中海进行的综合调查很少，以分析降水中氧和氢稳定同位素与气象变量之间的统计关系。为了了解地中海地区这一地区目前调节降雨稳定同位素特征的因素，我们选择了托斯卡纳地区（意大利中部），因为它具有相当大的气候季节性、复杂的形态和地形。托斯卡纳受到西北大西洋大气扰动和起源于地中海的潮湿气团的影响，也受到热那亚湾次生气旋中心的影响，热那亚湾是整个地中海最活跃的中心。因此，托斯卡纳地区的理想位置为研究湿气源对降雨同位素组成的复杂影响提供了机会。此外，在该地区进行了许多水文地质和古水文研究，需要更精确和定量的解释。因此，托斯卡纳地区的理想位置为研究湿气源对降雨同位素组成的复杂影响提供了机会。此外，在该地区进行了许多水文地质和古水文研究，需要更精确和定量的解释。因此，托斯卡纳地区的理想位置为研究湿气源对降雨同位素组成的复杂影响提供了机会。此外，在该地区进行了许多水文地质和古水文研究，需要更精确和定量的解释。

在这项工作中，644个同位素月度数据（δ ¹⁸ O，δ ²1971 年至 2018 年在托斯卡纳的 12 个地点收集的降水中的 H 和氘过量）被收集在一个数据库中。然后，仅考虑对月度数据覆盖近一年的站点进行处理，从而获得553个降水样本以及月平均气温和降雨量。在这个框架中，托斯卡纳的 LMWL 是通过应用不同的回归技术和统计分析来确定的，以确定气象和地理变量对降雨同位素组成的影响。结果指出降雨同位素特征的变化是由于几个气候和地理变量而不是局部温度和降水量的单一代理。大西洋和地中海的水分来源对产生观测到的同位素变异的贡献不同，它们的影响可能会随季节而变化。总体而言，温度和数量效应可以解释 50% 的同位素变异，但温度似乎更为重要。这些局部效应在降雨量少的时期（春季和夏季）更为明显，而大规模过程（水分起源、轨迹和降雨）则在冬季和秋季盛行。海拔效应是同位素空间变异的主要驱动因素。氘过量参数被证明是一个非常复杂但有用的信号，可以解开托斯卡纳降水中大西洋和地中海来源的不同贡献，即使它有时会被误用。它们的影响可能会随季节而变化。总体而言，温度和数量效应可以解释 50% 的同位素变异，但温度似乎更为重要。这些局部效应在降雨量少的时期（春季和夏季）更为明显，而大规模过程（水分起源、轨迹和降雨）则在冬季和秋季盛行。海拔效应是同位素空间变异的主要驱动因素。氘过量参数被证明是一个非常复杂但有用的信号，可以解开托斯卡纳降水中大西洋和地中海来源的不同贡献，即使它有时会被误用。它们的影响可能会随季节而变化。总体而言，温度和数量效应可以解释 50% 的同位素变异，但温度似乎更为重要。这些局部效应在降雨量少的时期（春季和夏季）更为明显，而大规模过程（水分起源、轨迹和降雨）则在冬季和秋季盛行。海拔效应是同位素空间变异的主要驱动因素。氘过量参数被证明是一个非常复杂但有用的信号，可以解开托斯卡纳降水中大西洋和地中海来源的不同贡献，即使它有时会被误用。但温度似乎更重要。这些局部效应在降雨量少的时期（春季和夏季）更为明显，而大规模过程（水分起源、轨迹和降雨）则在冬季和秋季盛行。海拔效应是同位素空间变异的主要驱动因素。氘过量参数被证明是一个非常复杂但有用的信号，可以解开托斯卡纳降水中大西洋和地中海来源的不同贡献，即使它有时会被误用。但温度似乎更重要。这些局部效应在降雨量少的时期（春季和夏季）更为明显，而大规模过程（水分起源、轨迹和降雨）则在冬季和秋季盛行。海拔效应是同位素空间变异的主要驱动因素。氘过量参数被证明是一个非常复杂但有用的信号，可以解开托斯卡纳降水中大西洋和地中海来源的不同贡献，即使它有时会被误用。