Water isotope ratio (d2H and d18O) measurements in atmospheric moisture using an optical feedback cavity enhanced absorption laser spectrometer

International audienceWater vapor isotopes represent an innovative and excellent tool for understanding complex mechanisms in the atmospheric water cycle over different time scales, and they can be used for a variety of applications in the fields of paleoclimatology, hydrology, oceanography, and ecology. We use an ultrasensitive near‐infrared spectrometer, originally designed for use on airborne platforms in the upper troposphere and lower stratosphere, to measure the water deuterium and oxygen‐18 isotope ratios in situ, in ground‐level tropospheric moisture, with a high temporal resolution (from 300 s down to less than 1 s). We present some examples of continuous monitoring of near‐surface atmospheric moisture, demonstrating that our infrared laser spectrometer could be used successfully to record high‐concentration atmospheric water vapor mixing ratios in continuous time series, with a data coverage of ∼90%, interrupted only for daily calibration to two isotope ratio mass spectrometry–calibrated local water standards. The atmospheric data show that the water vapor isotopic composition exhibits a high variability that can be related to weather conditions, especially to changes in relative humidity. Besides, the results suggest that observed spatial and temporal variations of the stable isotope content of atmospheric water vapor are strongly related to water vapor transport in the atmosphere

Dynamic of the atmospheric boundary layer from the isotopic composition of surface water vapor at the Maïdo Observatory (LaRéunion, Indian Ocean)

International audienceProjections of tropical and subtropical precipitation strongly differ from one climate model to another, both insign and in amplitude. This is the case for example in some parts of the West Indian Ocean. The causes of thoseuncertainties are numerous and a better understanding of humid processes in the tropical atmosphere is needed.We propose to address this burning question by using water stables isotopes.We have been measuring the isotopic composition of surface water vapor at the atmospheric Observatoryof Maïdo located at La Reunion Island (21◦S, 55◦E, 2200m a.s.l) since November 2014. Our results exhibit astrong diurnal cycle all over the year (except during cyclonic activity), with almost constant isotopic values duringthe day (around -13.5±0.6h for oxygen 18 from November 2014 to November 2015) and variable and verydepleted isotopic values during the night (down to -35h for oxygen 18 over the same period) associated with lowhumidity levels. We will show in this presentation that the diurnal isotopic variations are associated to a strongair masses mixing. During the day, the isotopic composition of the vapor is typical of marine boundary layer(BL) moisture transported from the close Ocean and lifted up to the Maïdo station. During the night, the depletedvalues and the low humidity could trace free troposphere moisture, which is consistent with previous studiessuggesting that the Maïdo Observatory is above the BL during the night. We will explore the influence of the dailyBL development on our observations, using a set of atmospheric vertical profiles done on site in May 2015 duringthe BIOMAIDO campaign. At last, we will discuss the most isotopic depleted values recorded in our observationsduring the night as a possible consequence of regional strong subsidences

Is the Isotopic Composition of Precipitation a Robust Indicator for Reconstructions of Past Tropical Cyclones Frequency? A Case Study on Réunion Island From Rain and Water Vapor Isotopic Observations

International audienceTropical cyclones (TCs) are among the natural hazards responsible for the highest human and economic losses. According to the WMO (World Meteorological Organization), 7 of the 10 costliest natural disasters in the past 50 years are TCs, including three cyclones in 2017: Harvey (which caused nearly $97 billion in damage), Maria (nearly$70 billion) and Irma (nearly $60 billion) (WMO, 2021). These three cyclones alone accounted for 35$164 billion in losses. In terms of human losses, the 10 deadliest natural disasters between 1970 and 2019 include 3 TCs: in Bangladesh in 1970 (cyclone Bhola) and in 199

Water and cellulose stable isotopes in northern Patagonia

The data set contains 5-min resolution meteorological data (temperature and relative humidity), 5-min resolution isotopic composition of water vapor, isotopic composition of precipitation for 11 rain events, isotopic composition of 10 river samples, isotopic composition of 6 leaf water samples and isotopic composition of 5 cellulose samples. The data are in February and March 2017. The site location is 41°47.412'S, 71°34.355'W, 1175 m