Temporal and spatial variations in stable isotopic compositions of precipitation during the typhoon Lekima (2019), China

Abstract

A clear understanding of factors governing stable isotopic variations in precipitation of tropical cyclones is critical for constraining atmospheric hydrological model simulations. The temporal and spatial variations in stable isotopic compositions of precipitation during the typhoon Lekima (2019) were investigated, based on rainwater samples collected at four sampling sites along its track between August 10 and August 12, 2019. Results showed that the δ18O and δD values of rainwater samples varied from −15.5‰ to −2.9‰ and from −112.4‰ to −17.3‰, respectively. The large ranges of δ18O and δD values in rainwater from the typhoon Lekima were most likely caused by the changes in rainfall intensity and its complex interaction with local water vapor. In addition, it was observed that the δ18O and δD values gradually decreased from the outer rainbands to the inner rainbands, and their values were more depleted of heavy isotopes than those of local rain. We speculated that both the high stratiform precipitation fractions and the deep convection system may be responsible for the isotopic depletion of rainwater related with the typhoon Lekima. It reveals that the rain type fractions and the intensity of convection should be considered in the elucidation of δ18O signals in extreme precipitation events. This study also has important implications for understanding atmospheric moisture cycles in tropical cyclones.