A comparative study on isotopic composition of precipitation in wet tropic and semi-arid stations across southern India

Abstract

Isotopic composition of monthly composite precipitation samples from Kozhikode (n = 31), a wet tropic station and Hyderabad (n = 25), a semi-arid station across southern India were studied for a period of four years from 2005 to 2008. During the study period, the Kozhikode station recorded an average rainfall of 3500 mm while the Hyderabad station showed an average rainfall of 790 mm. The average stable isotope values in precipitation at the Kozhikode station were δ 18 O = −3.52‰, d-excess = 13.72‰; δ 18 O = −2.94‰, d-excess = 10.57‰; and δ 18 O = −7.53‰, d-excess = 13.79‰, respectively during the pre-monsoon (March-May), monsoon (June-September) and post-monsoon (October-February) seasons. For the Hyderabad station, the average stable isotope values were δ 18 O = −5.88‰, d-excess = 2.34‰; δ 18 O = −4.39‰, d-excess = 9.21‰; and δ 18 O = −8.69‰, d-excess = 14.29‰, respectively for the three seasons. The precipitation at the two stations showed distinctive isotopic signatures. The stable isotopic composition of precipitation at the Hyderabad station showed significant variations from the global trend while the Kozhikode station almost followed the global value. These differences are mainly attributed to the latitudinal differences of the two stations coupled with the differences in climatic conditions.

Identifying moisture transport pathways for north‐west India

“…This can be attributed to the variation in vapour sources, mixing of vapour masses for a shorter period under favourable conditions, cloud dynamics and local moisture recycling (Aggarwal et al, 2012; Lekshmy et al, 2015; Theeuwen et al, 2023). It is also challenging for the Indian sub‐continent to understand the hydro‐meteorological processes due to the dual monsoon system from the Bay of Bengal and the Arabian Sea (Breitenbach et al, 2010; Deshpande et al, 2013; Midhun et al, 2018; Oza et al, 2020; Warrier & Babu, 2011; Wen et al, 2012).…”

Holocene precipitation hydrogen isotopic values on Nilgiri Plateau (southern India) suggest a combined effect of precipitation amount and transport paths

“…As the study area receives SWM and NEM, it is important to characterize their isotopic composition. Four Global Network of Isotopes in Precipitation (GNIP) (IAEA/WMO, 2022) stations and a few year-long investigations (Supplemental Table S1, available online; Deshpande et al, 2003; Lekshmy et al, 2015; Warrier et al, 2010; Yadava et al, 2007) reveal that the NEM is relatively more depleted in the heavy isotopes than the SWM. The differences in the δD of SWM and NEM at GNIP stations varied from 9‰ to 26‰.…”

Stable water isotope signatures of dual monsoon precipitation: A case study of Greater Cochin region, south-west coast of India

“…Only few SWI studies on precipitation samples have been carried out in Kerala (Soman et al 1988;Unnikrishnan Warrier and Babu 2011;Lekshmy et al 2014;Resmi et al 2016;Unnikrishnan Warrier et al 2015). The present study area of Greater Cochin is located in the central part of Kerala, which is classed as a Tier-II metro in India.…”