Stable Isotope Characteristics for Precipitation Events and Their Responses to Moisture and Environmental Changes During the Summer Monsoon Period in Southwestern China

Abstract

Samples of hydrogen and oxygen stable isotopes in precipitation collected and analyzed during the summer monsoon in 2017 and 2018 in Chengdu are reported in this paper. Increasing (decreasing) trends of isotope values (δD and δ 18 O) occur from May to June (September to October), and the valleys occur from July to August. The correlation between δD and δ 18 O for both precipitation events and monthly average precipitation is significant, with high R 2 values (≥0.98). The differences in regression lines may be due to the comprehensive influence of moisture sources, transport path and sub-cloud processes. Combining the d-excess values of precipitation and air mass trajectories generated by the HYSPLIT model, precipitation with a low (high) d-excess value and a more (less) negative δ 18 O corresponds to moisture from ocean (inland) sources. The δ 18 O-temperature (T) and δ 18 O-precipitation (P) correlations are not significant and vary greatly among different periods, which may be attributed to the mutual masking of different effects and the influence of atmospheric circulation processes. The results imply that the negative values in biological and geological proxies may be related to warmer climate, higher precipitation and a larger contribution of oceanic monsoon precipitation, but cannot indicate the changes in temperature and precipitation quantifiably.

Spatial and temporal distributions of stable isotopes in precipitation over Thailand

“…Correspondingly, understanding how the stable isotopic composition of precipitation is controlled by its formation (Genereux & Hooper, 1998) and knowledge of the spatio‐temporal variations in stable hydrogen and oxygen isotopic ratios of precipitation (δ 2 H and δ 18 O) are equally important in the field of isotope hydrology (Bedaso et al, 2020; Lemma et al, 2020; Li et al, 2017; Sun et al, 2016). Stable isotopes play a significant role in observing, reconstructing, and understanding past and present climatic conditions (Jiao et al, 2020; Rozanski et al, 1997; Xia et al, 2020). The dominant factor describing the spatial and temporal distribution of isotopes in precipitation was attributed mainly to the amount effect in the tropics (Araguás‐Araguás et al, 1998), while the temperature effect was more pronounced in high‐latitude regions (Ichiyanagi, 2007).…”

Water cycling and partitioning through the soil–plant–atmosphere continuum in a subtropical, urban woodland inferred by water stable isotopes

“…Only results showing ‘norm’ were further used. Details of sample preparation and analysis can be found in Chen et al (2020) and Xia et al (2020). The measurement results are expressed in terms of the conventional deviation value ( δ ‐value) relative to the Vienna Standard Mean Ocean Water (V‐SMOW) (Coplen, 2011): $$$$ \delta \left({\mbox{\fontencoding{U}\fontfamily{wasy}\selectfont\char104}} \right)=\left[\left({R}_{\mathrm{sample}}-{R}_{\mathrm{standard}}\right)/{R}_{\mathrm{standard}}\right]\times 1{0}^3, $$$$ where R sample and R standard are isotopic ratios ( 2 H/H or 18 O/ 16 O) in the samples and references, respectively.…”

“…Only results showing 'norm' were further used. Details of sample preparation and analysis can be found in Chen et al (2020) and Xia et al (2020). The measurement results are expressed in terms of the conventional deviation value (δ-value) relative to the Vienna Standard Mean Ocean Water (V-SMOW) (Coplen, 2011):…”

Response of Ecological Environment to Climate Change in the Source Area of the Yangtze River Based on the Observation During 2005-2015

“…Climate change is the decisive factor for vegetation growth and precipitation change is main factor for affecting ecological environment change [37][38]. Through correlation analysis and annual variation, there was a significant negative correlation between precipitation and vegetation height (Fig.…”