Studies on stable isotopic composition of daily rainfall from Kozhikode, Kerala, India

The isotopic variations δ 18 O, δ 2 H and d -excess in daily rainfall ranged from δ 18 O: −4.4 to 2 ‰, δ 2 H: −25.3 to 13.8 ‰, and d -excess: −2.4 to 15.3 ‰; δ 18 O: −9.7 to −0.6 ‰, δ 2 H: −61.7 to 5.3 ‰, and d -excess 5.8 to 17.4 ‰; δ 18 O −11.3 to −1.4 ‰, δ 2 H: −75.3 to 0.9 ‰, and d -excess: 8.8 to 21.3 ‰ during the pre-, southwest and northeast monsoon periods, respectively.

Thus, daily rainfall events during two monsoon periods had a distinct range of isotopic variations. The daily rain events within the two monsoon seasons also exhibited periodic variations. The isotopic composition of rain events during pre-monsoon and a few low-intensity events during the southwest monsoon period had imprints of secondary evaporation.