Assessing moisture sources of precipitation in the Western Pamir Mountains (Tajikistan, Central Asia) using deuterium excess

Abstract

Air moisture of oceanic origin can be subject to long-range transport and could contribute to precipitation at distant places. With ongoing climate change the relationship between water vapour sources and sinks is under constant evolution and plays an important role for water budget assessments. This study analysed monthly integrated and event-based precipitation samples from two field sites in the Western Pamir Mountains (Tajikistan) for stable isotope compositions of oxygen (d 18 O) and hydrogen (d 2 H) of water. The aim was to investigate water vapour sources and, in particular, to evaluate contributions of water vapour from the Mediterranean region. The latter has been often postulated as a potential moisture source region for Central Asia. Deuterium excess values (d), that serve as a fingerprint of moisture origin, were below 13& in monthly integrated samples, for most of the year. This indicates a smaller contribution of high Mediterranean moisture ($20&) to the Western Pamir Mountains than originally expected. A maximum d value of 19& was observed in March, which is not in agreement with the common observation of increased Mediterranean contribution during winter (DJF). A Lagrangian backward trajectory model (HYSPLIT) was applied to infer the general air mass origin for sampled precipitation events. A maximum contribution of 'western' moisture of 40% was also detected in March, while 40%-60% of moisture that contributed to precipitation events in winter was transported by trajectories that originated from the Northern Indian Ocean.

Developing Meteoric Water Lines for Iran Based on Air Masses and Moisture Sources

“…The source of the moisture is the most important predictor of the isotope content of precipitation [1,8]. There are numerous numerical models to study moisture sources, but a Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) [9] model has been used in numerous stable isotope studies for tracking moisture sources of precipitation [5,10,11]. Some of these studies, such as [11], consider d-excess as reliable fingerprints to study moisture sources responsible for precipitation.…”

“…There are numerous numerical models to study moisture sources, but a Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) [9] model has been used in numerous stable isotope studies for tracking moisture sources of precipitation [5,10,11]. Some of these studies, such as [11], consider d-excess as reliable fingerprints to study moisture sources responsible for precipitation. Moisture released from water bodies with a high sea surface temperature (SST) and a low relative humidity normally show a high d-excess (d-excess = δ 2 H − 8 × δ 18 O [12]), whereas precipitation originating from water bodies with a low SST and a high relative humidity will normally have a moderate to low d-excess [12][13][14].…”

Tritium as a hydrological tracer in Mediterranean precipitation events

“…Data availability. Sample data can be accessed on the PANGAEA online data repository (https://doi.org/10.1594/PANGAEA.911474; Juhlke et al, 2020). Third party data used in this study include data from the IAEA/WMO GNIP program and the Copernicus Climate Change Service (C3S).…”

Hydrochemical differences between river water and groundwater in Suzhou, Northern Anhui Province, China

“…Moreover, several studies have found that evaporation and water rock interaction can increase the δ 18 O in the water, then leading to the decrease of d-excess [33,34]. In this study, the d-excess of RW samples ranges from −4.5 to 5.7‰ (mean = −0.2‰), which is lower than the d-excess value of atmospheric precipitation ( Table 1 and Figure 5), and therefore, the river water might have been affected by evaporation.…”