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  • 1
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    Stable Isotope Composition of Cyclone Mekunu Rainfall, Southern Oman (2020)
    Details
    Publication Date: 2023-02-08
    Description: Cyclone Mekunu hit the southern Arabian Peninsula in late May 2018 and brought rainfall amounts that accounted for up to 6 times the mean annual precipitation. Coming from the Arabian Sea, a quite underdocumented region with regard to cyclones, the storm eye crossed the Omani coast approximately 80 km east of the border to Yemen. Using automatic samplers, rainfall samples were collected during the event at three locations along a transect almost parallel to the storm track. The stable isotope analyses show a wide range of δ values, with minimum and maximum values of −17.01‰ δ18O and −1.77‰ δ18O and −122.2‰ δ2H and −1.6‰ δ2H. On average, rainfall becomes isotopically lighter with elevation, but rather irregularly. In view of high wind speeds probably precluding a gradual rainout of ascending air masses, a “pseudo elevation effect” seems likely. Our measurements expand the known δ value range of local cyclones by about 6‰ for δ18O and by nearly 50‰ for δ2H. The isotopic composition of the annual Indian Summer Monsoon shows values of −0.93‰ δ18O to 2.21‰ δ18O and −2.1‰ δ2H to 23.7‰ δ2H. Thus, there is a clear difference in the dual isotope signatures of the two precipitation systems in the area. Our findings enable an assessment of the impact of cyclones on the hydro(geo)logical system. For the arid Najd area, we demonstrate that the isotopic signatures of groundwater samples fall between those of cyclone and (paleo)monsoon precipitation, suggesting that several rainfall types may have contributed to replenishment.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Chemical composition of monsoon bulk precipitation in the Salalah area, Oman (2023)
    Elsevier
    Details
    Publication Date: 2024-02-07
    Description: Precipitation chemistry data provide important information for environmental studies on large-scale element cycling and anthropogenic impacts on our atmosphere, but also for hydrochemical models and groundwater recharge estimations via the Chloride Mass Balance method. Such recharge data play a crucial role in groundwater management, particularly in (semi-)arid areas. Unfortunately, precipitation analyses are often scarce in such regions. This also applies to the Arabian Peninsula, including southern Oman. To overcome this lack of rain chemistry data, we developed a strategy for automatic weekly bulk precipitation sampling, using recently designed automatic rainwater samplers. The integral samples were gathered along an elevation gradient from the Salalah coast to the Dhofar mountains during the Indian Ocean Monsoon seasons 2017 and 2018. Our major ion analyses of the rainwater samples revealed considerable temporal and spatial heterogeneity, in terms of ion proportions and absolute concentrations. Samples from the coast were relatively salty (EC mostly 〉3000 μS cm−1) and rich in Na+ and Cl−, reflecting small rain amounts and a sea spray effect. Further inland, solute concentrations were lower, partly due to more precipitation, and ions such as Ca2+ and SO42− gained importance, probably due to calcite and gypsum dust. This pattern reflects the interplay between solute availability (influenced by regional geology, wind direction at different altitudes, and wind speed) and precipitation amounts. Cl−/Br− ratios were fairly uniform and scattered around the seawater value. Combining ion concentrations and rain amounts yielded bulk depositions that showed an erratic pattern along the elevation gradient, i.e., depositions did not decrease steadily in inland direction, as one may assume. This suggests that the occasionally reported approach of collecting a few opportunistic grab samples at a single site is unlikely to yield data that are representative for a larger coastal study area.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: text
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Stable Isotope Composition of Cyclone Mekunu Rainfall, Southern Oman (2021)
    Details
    Publication Date: 2021-07-04
    Description: Cyclone Mekunu hit the southern Arabian Peninsula in late May 2018 and brought rainfall amounts that accounted for up to 6 times the mean annual precipitation. Coming from the Arabian Sea, a quite underdocumented region with regard to cyclones, the storm eye crossed the Omani coast approximately 80 km east of the border to Yemen. Using automatic samplers, rainfall samples were collected during the event at three locations along a transect almost parallel to the storm track. The stable isotope analyses show a wide range of δ values, with minimum and maximum values of −17.01‰ δ18O and −1.77‰ δ18O and −122.2‰ δ2H and −1.6‰ δ2H. On average, rainfall becomes isotopically lighter with elevation, but rather irregularly. In view of high wind speeds probably precluding a gradual rainout of ascending air masses, a “pseudo elevation effect” seems likely. Our measurements expand the known δ value range of local cyclones by about 6‰ for δ18O and by nearly 50‰ for δ2H. The isotopic composition of the annual Indian Summer Monsoon shows values of −0.93‰ δ18O to 2.21‰ δ18O and −2.1‰ δ2H to 23.7‰ δ2H. Thus, there is a clear difference in the dual isotope signatures of the two precipitation systems in the area. Our findings enable an assessment of the impact of cyclones on the hydro(geo)logical system. For the arid Najd area, we demonstrate that the isotopic signatures of groundwater samples fall between those of cyclone and (paleo)monsoon precipitation, suggesting that several rainfall types may have contributed to replenishment.
    Description: Key Points: We conducted high‐resolution sampling of a tropical cyclone from the Arabian Sea for stable isotope and hydrochemical analyses. The strong depletion in heavy isotopes and large intra‐event variations confirm observations from tropical storms elsewhere. There was no overlap with the isotopic fingerprint of local monsoon rains.
    Description: The Research Council (TRC) http://dx.doi.org/10.13039/501100004787
    Description: The Research Council of Oman
    Keywords: 551.5 ; tropical cyclone ; stable isotopes ; precipitation ; paleoclimate ; Oman ; Arabian Sea
    Type: article
    Location Call Number Limitation Availability
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    CITATION GEO-LEO
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