TY - JOUR

T1 - Spatiotemporal variation of stable isotopic composition in precipitation

T2 - Post-condensational effects in a humid area

AU - Müller, Sascha

AU - Stumpp, Christine

AU - Sørensen, Jens Havskov

AU - Jessen, Søren

PY - 2017

Y1 - 2017

N2 - In the present study, a 2-year dataset on δ18O and δ2H in precipitation is used to investigate hydrometeorologic controls on the isotopic compositions in a temperate maritime climate. Data was collected in Denmark along a transect of Six sampling stations across a landscape with a small topographic gradient and predominant westerly winds. Data showed the local meteoric water line for this region is expressed by the equation δ2H = 7.4δ18O + 5.4‰. A significant trend correlating enriched isotopic values to humidities around 70% during dry season and more depleted isotopic values to humidities around 90% during wet season was derived from the dataset. Temperature was found to only influence the isotopic composition in a secondary way, whereas no significant relationship was obtained for precipitation amount and evapotranspiration. It is suggested that subcloud post-condensation exchange strongly influences the isotopic composition at the study site. A simple model of evaporation on falling rain was applied with the aim to reproduce observational data and show the potential influence of changing humidity conditions on precipitation compositions. The rather simple model approach did not fully explain the observational data, but it highlights the drastic isotopic changes from a falling raindrop that potentially can occur due to its release into a dryer atmosphere. This study shows that regional conditions and especially humidity can alter the isotopic composition in precipitation substantially even in regions without major topographic and hydrometeorologic gradients.

AB - In the present study, a 2-year dataset on δ18O and δ2H in precipitation is used to investigate hydrometeorologic controls on the isotopic compositions in a temperate maritime climate. Data was collected in Denmark along a transect of Six sampling stations across a landscape with a small topographic gradient and predominant westerly winds. Data showed the local meteoric water line for this region is expressed by the equation δ2H = 7.4δ18O + 5.4‰. A significant trend correlating enriched isotopic values to humidities around 70% during dry season and more depleted isotopic values to humidities around 90% during wet season was derived from the dataset. Temperature was found to only influence the isotopic composition in a secondary way, whereas no significant relationship was obtained for precipitation amount and evapotranspiration. It is suggested that subcloud post-condensation exchange strongly influences the isotopic composition at the study site. A simple model of evaporation on falling rain was applied with the aim to reproduce observational data and show the potential influence of changing humidity conditions on precipitation compositions. The rather simple model approach did not fully explain the observational data, but it highlights the drastic isotopic changes from a falling raindrop that potentially can occur due to its release into a dryer atmosphere. This study shows that regional conditions and especially humidity can alter the isotopic composition in precipitation substantially even in regions without major topographic and hydrometeorologic gradients.

KW - humidity effects

KW - local meteoric waterlines

KW - post-condensation effects

KW - precipitation

KW - stable isotopes

KW - δO/δH

U2 - 10.1002/hyp.11186

DO - 10.1002/hyp.11186

M3 - Journal article

AN - SCOPUS:85026317088

VL - 31

SP - 3146

EP - 3159

JO - Hydrological Processes

JF - Hydrological Processes

SN - 0885-6087

IS - 18

ER -