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Stable Isotope Composition of Cyclone Mekunu Rainfall, Southern Oman
Water Resources Research ( IF 5.4 ) Pub Date : 2020-10-20 , DOI: 10.1029/2020wr027644
Thomas Müller 1, 2 , Jan Friesen 3 , Stephan M. Weise 3 , Omar Al Abri 4 , Ali Bakhit Ali Bait Said 5 , Nils Michelsen 6
Affiliation  

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.

中文翻译:

阿曼南部旋风Mekunu降雨的稳定同位素组成

飓风Mekunu于2018年5月下旬袭击了阿拉伯半岛南部,带来的降水量高达年平均降水量的6倍。风暴眼来自阿拉伯海(关于飓风的文献资料很少),风暴眼越过了阿曼海岸,距也门边界以东约80公里。使用自动采样器,在活动期间沿几乎平行于风暴径的横断面的三个位置收集了降雨样本。稳定同位素分析表明了广泛的δ值,以最小和-17.01‰的最大值δ 18 O和-1.77‰ δ 18 O和-122.2‰ δ 2 H和-1.6‰ δ 2H.平均而言,降雨随着海拔升高同位素变轻,但不规则。鉴于高风速可能会阻止逐渐上升的气团降雨,“伪高程效应”似乎很可能出现。我们的测量扩展已知δ本地气旋约6‰值范围为δ 18 O和近50‰,δ 2的-0.93‰的年度印度夏季风节目值H的同位素组成δ 18 O操作2.21‰ δ 18 O和-2.1‰ δ 2 H至23.7‰ δ 2H.因此,该地区两个降水系统的双重同位素特征明显不同。我们的发现可以评估旋风对水文(地质)系统的影响。对于干旱的纳吉德地区,我们证明了地下水样品的同位素特征介于旋风和(古)季风降水之间,表明几种降雨类型可能有助于补给。
更新日期:2020-12-15
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