Influence of air mass trajectories on precipitation stable isotopes in Damascus, Syria – Statistical analysis of daily and monthly rainfall sampling

Abstract

Abstract Ratios of the stable isotopes (δ18O and δ2H) and deuterium excess (d-excess) values in daily and monthly composite rainwater (RW) samples collected at the Damascus area over a period of 12 years were determined to evaluate the influence of air mass trajectories on their variability. The HYSPLIT model was used for simulating the back air mass trajectories and computation of the key meteorological parameters along the trajectory path of the air masses producing single rain events. Eight major trajectory classes were distinguished for the potential rain events occurred during the studied period. The fractions of the trajectories came from the North Atlantic Ocean (AO), North Pole (NP) and the Mediterranean Sea (MS) were the highest (total ≈ 85%), whereas those of the trajectories came from the Black Sea (BS), Arabian Sea (AS) and Arabian Gulf (AG) were the lowest (each class is < 5%). The daily RW samples associated with the Siberian plateau (SP), AO, NP, MS and to some extent north Africa (NA) air masses were isotopically the most depleted (δ18O <–4‰, δ2H <–25‰, and d–excess > 10‰), whereas those coupled with the trajectories came from the BS, AS, and AG were isotopically the most enriched ​​(–2.5‰ < δ18O < − 1.0‰ and d-excess < 10‰). The findings from this study may offer new insights to better understand the effects of air mass trajectories on precipitation stable isotopes in the Eastern Mediterranean region.