The Significance of Hydrogen and Oxygen Stable Isotopes in the Water Vapor Source in Dingxi Area

Deuterium excess and stable oxygen isotopes in precipitation have been widely applied to trace the source of water vapor. In this study, hydrogen and oxygen isotope analyses of samples were collected on seven sampling stations in Dingxi area from April 2019 to April 2020. The seasonal variation of hydrogen and oxygen stable isotopes as well as the d-excess indicate that the source of water vapor in Dingxi area is mostly from a single source. However, there are different sources of water vapor in the summer. Meanwhile, water vapor sources were analyzed using the Lagrange algorithm, indicating two different principal water vapor sources for precipitation in the area: some locally recycled water vapor in summer and autumn, and most water vapor from the westerly belt. Further studies using the PSCF and CWT analysis methods show that the locally recycled water vapor contributes more to its precipitation in the northwest of Dingxi area.

Deuterium Excess in Precipitation Reveals Water Vapor Source in the Monsoon Margin Sites in Northwest China

The deuterium excess (d) in precipitation, determined by the stable hydrogen and oxygen isotopes (δ2H and δ18O), is a widely applied parameter in tracing the water vapor source. Based on the multiple-year observations of stable water isotopes in precipitation at four stations in the Lanzhou city, Northwest China, we analyzed the variations in deuterium excess in precipitation at the Asian monsoon margin region. The mean value of deuterium excess at the study region is 11.0‰ in the dry season and 8.0‰ in the wet season. The d value in precipitation negatively correlates with air temperature and vapor pressure. The low d value during the wet season reflects the monsoon moisture transported from long distances. During the dry season, the continental air masses correspond to the higher d value in precipitation. The moisture regimes based on reanalysis data are generally consistent with the findings using a stable isotopic approach, and the monsoon moisture is highlighted in summer precipitation at these monsoon margin sites.

Investigating the Interannual Variability of the Boreal Summer Water Vapor Source and Sink over the Tropical Eastern Indian Ocean-Western Pacific

Using the four-times daily and monthly-mean reanalysis datasets of NCEP/NCAR for the 1958 to 2018 period, we investigate the interannual variability of the June-July-August (JJA)–mean water vapor source and sink over the tropical eastern Indian Ocean-Western Pacific (TEIOWP) and the underlying mechanism. It is found that the two major modes (EOF1 and EOF2) of the water vapor source and sink anomalies over the TEIOWP present a southwest-northeast oriented dipole and a southwest-northeast oriented tripole. Specifically, when the western maritime continent shows an anomalous water vapor source, the northwestern Pacific is characterized by anomalous water vapor sink and source in EOF1 and EOF2 modes, respectively. The EOF1 and EOF2 modes are primarily driven by a single and a double meridional cell anomaly, which corresponds to the in-phase and out-of-phase linkage between evaporation anomalies over the western maritime continent and precipitation anomalies over the northwestern Pacific, respectively. Furthermore, the EOF1 mode is regulated by the quick transition of the El Niño-Southern Oscillation (ENSO) phase, whereas the EOF2 mode probably originates from internal atmospheric variability. Considering that the standard deviation of PC1 is much higher during ENSO years than that during non-ENSO years, it is probable that the water source and sink anomalies over the TEIOWP tend to be dominant by EOF1 mode during ENSO years. In contrast, the EOF2 mode may play an important role in the water source and sink anomalies over the TEIOWP during non-ENSO years. Accordingly, the water vapor source and sink anomalies over the TEIOWP may be well predicted based on the ENSO state in the previous December-January-February. These results are useful for understanding the predictability of water vapor source and sink anomalies over the TEIOWP.

Identification of moisture source region based on trajectory model analysis and isotopic composition of the precipitation in Debrecen, Hungary

<p>In this study, we focus on the relationship between the water vapor source region and the isotopic composition of the precipitation. The change of isotope characteristics of precipitation depends on the moisture source region. Long-term stable isotope (δ<sup>18</sup>O, δ<sup>2</sup>H ) measurements of precipitation were performed in Debrecen, Hungary, between 2001 and 2014. The long-term isotope time series and trajectory modeling are suitable for determining moisture source regions. Backward trajectory analysis was carried out using the Lagrangian Raptor model based on ERA5 atmospheric data. Hourly backward trajectories were calculated for Debrecen for the days with precipitation in the period between 2001-2014.</p><p>Based on the study three source regions were identified. Of these, 60% represented the Carpathian Basin, which is where most of the moisture evaporated from near the surface. The remaining 40% of the northwest and southwest were represented by moisture source regions. This means that the isotopic composition of precipitation significantly determines the local and continental effects, i.e. the moisture evaporated from the continental surface contributes significantly to the spatial and temporal variation of the precipitation isotope composition.</p>

Water Vapor from Western Eurasia Promotes Precipitation during the Snow Season in Northern Xinjiang, a Typical Arid Region in Central Asia

Atmospheric water vapor plays an important role in the water cycle, especially in arid Central Asia, where precipitation is invaluable to water resources. Understanding and quantifying the relationship between water vapor source regions and precipitation is a key problem in water resource research in typical arid Central Asia, Northern Xinjiang. However, the relationship between precipitation and water vapor sources is still unclear of snow season. This paper aimed at studying the role of water vapor source supply in the Northern Xinjiang precipitation trend, which was investigated using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. The results showed that the total water vapor contributed from Western Eurasia and the North Polar area presented upward trends similar to the precipitation change trend, which indicated that the water vapor contribution from the two previous water vapor source regions supplied abundant water vapor and maintained the upward precipitation trend from 1980 to 2017 in Northern Xinjiang. From the climatology of water vapor transport, the region was controlled by midlatitude westerlies and major water vapor input from the western boundary, and the net water vapor flux of this region also showed an annual increasing trend. Western Eurasia had the largest moisture percentage contribution to Northern Xinjiang (48.11%) over the past 38 years. Northern Xinjiang precipitation was correlated with water vapor from Western Eurasia, the North Polar area, and Siberia, and the correlation coefficients were 0.66, 0.45, and 0.57, respectively. These results could aid in better understanding the water cycle process and climate change in this typical arid region of Central Asia.

Nonlinear Bending Mechanics of Hygroscopic Liquid Crystal Polymer Networks

A chemically responsive liquid crystal polymer network is experimentally characterized and compared to a nonlinear constitutive model and integrated into a finite element shell model. The constitutive model and large deformation shell model are used to understand water vapor induced bending. This class of materials is hygroscopic and can exhibit large bending as water vapor is absorbed into one side of the liquid crystal network (LCN) film. This gives rise to deflection away from the water vapor source which provides unique sensing and actuation characteristics for chemical and biomedical applications. The constitutive behavior is modeled by coupling chemical absorption with nonlinear continuum mechanics to predict how water vapor absorption affects bending deformation. In order to correlate the model with experiments, a micro-Newton measuring device was designed and tested to quantify bending forces generated by the LCN. Forces that range between 1 and 8 μN were measured as a function of the distance between the water vapor source and the LCN. The experiments and model comparisons provide important insight into linear and nonlinear chemically induced bending for a number of applications such as microfluidic chemical and biological sensors.