Assessing the Sampling Quality of a Low-Tech Low-Budget Volume-Based Rainfall Sampler for Stable Isotope Analysis

Fischer, Benjamin; Aemisegger, Franziska; Graf, Pascal; Sodemann, Harald; Seibert, Jan

doi:10.3389/feart.2019.00244

Cited by 8 publications

(6 citation statements)

References 28 publications

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“…The same sampling system has also been used by the IAEA in its Global Network for Isotopes in Precipitation. The uncertainty due to small-scale variability in rainfall was assessed in Europe in a dedicated study on 10 precipitation events with an array of similar samplers and found to be < 2 ‰ in δ 2 H and < 0.3 ‰ in δ 18 O (Fischer et al, 2019). The isotope composition of the collected water samples was analysed by cavity ring-down laser spectrometry (Picarro L2130-i, Picarro Inc., Santa Clara, CA, USA) in "high-precision mode" in the laboratory of the Chair of Hydrology at the University of Freiburg, Germany.…”

Section: Conditionsmentioning

confidence: 99%

“…Synopticscale ARWB events occur in situations with a meridionally extended undulation of the jet stream and appear in the shape of meridionally elongated and narrow tongues of potential vorticity (PV) on isentropic surfaces (McIntyre and Palmer, 1984;Appenzeller and Davies, 1992). The frequency of ARWB occurrence is higher over the eastern North Atlantic (20 %-30 %) than over the central North Atlantic (5 %-10 %; Wernli and Sprenger, 2007;Fröhlich and Knippertz, 2008;Martius and Rivière, 2016). During ARWB, the formation of elongated PV filaments (streamers) or isolated regions with stratospheric air (i.e.…”

Section: Overview Of Atmospheric Flow Conditions During Isotradesmentioning

confidence: 99%

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How Rossby wave breaking modulates the water cycle in the North Atlantic trade wind region

Aemisegger

Vogel²,

Graf

et al. 2021

Weather Clim. Dynam.

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Abstract. The interaction between low-level tropical clouds and the large-scale circulation is a key feedback element in our climate system, but our understanding of it is still fragmentary. In this paper, the role of upper-level extratropical dynamics for the development of contrasting shallow cumulus cloud patterns in the western North Atlantic trade wind region is investigated. Stable water isotopes are used as tracers for the origin of air parcels arriving in the sub-cloud layer above Barbados, measured continuously in water vapour at the Barbados Cloud Observatory during a 24 d measurement campaign (isoTrades, 25 January to 17 February 2018). These data are combined with a detailed air parcel back-trajectory analysis using hourly ERA5 reanalyses of the European Centre for Medium-Range Weather Forecasts. A climatological investigation of the 10 d air parcel history for January and February in the recent decade shows that 55 % of the air parcels arriving in the sub-cloud layer have spent at least 1 d in the extratropics (north of 35∘ N) before arriving in the eastern Caribbean at about 13∘ N. In 2018, this share of air parcels with extratropical origin was anomalously large, with 88 %. In two detailed case studies during the campaign, two flow regimes with distinct isotope signatures transporting extratropical air into the Caribbean are investigated. In both regimes, the air parcels descend from the lower part of the midlatitude jet stream towards the Equator, at the eastern edge of subtropical anticyclones, in the context of Rossby wave breaking events. The zonal location of the wave breaking and the surface anticyclone determine the dominant transport regime. The first regime represents the “typical” trade wind situation, with easterly winds bringing moist air from the eastern North Atlantic into the Caribbean, in a deep layer from the surface up to ∼600 hPa. The moisture source of the sub-cloud layer water vapour is located on average 2000 km upstream of Barbados. In this regime, Rossby wave breaking and the descent of air from the extratropics occur in the eastern North Atlantic, at about 33∘ W. The second regime is associated with air parcels descending slantwise by on average 300 hPa (6 d)−1 directly from the north-east, i.e. at about 50∘ W. These originally dry airstreams experience a more rapid moistening than typical trade wind air parcels when interacting with the subtropical oceanic boundary layer, with moisture sources being located on average 1350 km upstream to the north-east of Barbados. The descent of dry air in the second regime can be steered towards the Caribbean by the interplay of a persistent upper-level cut-off low over the central North Atlantic (about 45∘ W) and the associated surface cyclone underneath. The zonal location of Rossby wave breaking and, consequently, the pathway of extratropical air towards the Caribbean are shown to be relevant for the sub-cloud layer humidity and shallow-cumulus-cloud-cover properties of the North Atlantic winter trades. Overall, this study highlights the importance of extratropical dynamical processes for the tropical water cycle and reveals that these processes lead to a substantial modulation of stable water isotope signals in the near-surface humidity.

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Section: Conditionsmentioning

confidence: 99%

Section: Overview Of Atmospheric Flow Conditions During Isotradesmentioning

confidence: 99%

How Rossby wave breaking modulates the water cycle in the North Atlantic trade wind region

Aemisegger

Vogel²,

Graf

et al. 2021

Weather Clim. Dynam.

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show abstract

“…We used a Gaussian error propagation method (Genereux, 1998) to estimate the uncertainty in the calculated fractions of the source waters for the two-component hydrograph separation and EMMA. For the two-component hydrograph separation, we defined the uncertainty in the event and pre-event water composition as the standard deviation of the rainfall sampled during the event and groundwater sampled during the snapshot campaign closest to the event (see Table 1), respectively.…”

Section: Solutementioning

confidence: 99%

Do stream water solute concentrations reflect when connectivity occurs in a small, pre-Alpine headwater catchment?

Kiewiet

Meerveld

Stähli

et al. 2020

Hydrol. Earth Syst. Sci.

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Abstract. Expansion of the hydrologically connected area during rainfall events causes previously disconnected areas to contribute to streamflow. If these newly contributing areas have a different hydrochemical composition compared to the previously connected contributing areas, this may cause a change in stream water chemistry that cannot be explained by simple mixing of rainfall and baseflow. Changes in stormflow composition are, therefore, sometimes used to identify when transiently connected areas (or water sources) contribute to stormflow. We identified the dominant sources of streamflow for a steep 20 ha pre-Alpine headwater catchment in Switzerland and investigated the temporal changes in connectivity for four rainfall events based on stream water concentrations and groundwater level data. First, we compared the isotopic and chemical composition of stormflow at the catchment outlet to the composition of rainfall, groundwater and soil water. Three-component end-member mixing analyses indicated that groundwater dominated stormflow during all events, and that soil water fractions were minimal for three of the four events. However, the large variability in soil and groundwater composition compared to the temporal changes in stormflow composition inhibited the determination of the contributions from the different groundwater sources. Second, we estimated the concentrations of different solutes in stormflow based on the mixing fractions derived from two-component hydrograph separation using a conservative tracer (δ2H) and the measured concentrations of the solutes in baseflow and rainfall. The estimated concentrations differed from the measured stormflow concentrations for many solutes and samples. The deviations increased gradually with increasing streamflow for some solutes (e.g. iron and copper), suggesting increased contributions from riparian and hillslope groundwater with higher concentrations of these solutes and thus increased hydrological connectivity. The findings of this study show that solute concentrations partly reflect the gradual changes in hydrologic connectivity, and that it is important to quantify the variability in the composition of different source areas.

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“…The same sampling system has also been used by the IAEA in its Global Network for Isotopes in Precipitation. The uncertainty due to small scale variability of rainfall was assessed in Europe in a dedicated study on 10 precipitation events with an array of similar samplers and found to be < 2 ‰ in d 2 H and < 0.3 ‰ in d 18 O (Fischer et al, 2019). The isotope composition of the collected water samples was analysed by Cavity Ring-down laser spectrometry (Picarro L2130-i, Picarro Inc., Santa Clara, CA, USA) in 'high precision mode' in the Laboratory of the Chair of Hydrology at the University of Freiburg, Germany.…”

Section: Stable Water Isotope Measurements At the Barbados Cloud Obsementioning

confidence: 99%

How Rossby wave breaking modulates the water cycle in the North Atlantic trade wind region

Aemisegger¹,

Vogel²,

Graf³

et al. 2020

Preprint

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Abstract. The interaction between low-level tropical clouds and the large-scale circulation is a key feedback element in our climate system, but our understanding of it is still fragmentary. In this paper, the role of upper-level extratropical dynamics for the development of contrasting shallow cumulus cloud patterns in the western North Atlantic trade wind region is investigated. Stable water isotopes are used as tracers for the origin of air parcels arriving in the sub-cloud layer above Barbados, measured continuously in water vapour at the Barbados Cloud Observatory during a 24-day measurement campaign (isoTrades, 25 January to 17 February 2018). This data is combined with a detailed air parcel back-trajectory analysis using hourly ERA5 reanalyses of the European Centre for Medium Range Weather Forecasts. A climatological investigation of the 10-day air parcel history for January and February in the recent decade shows that 55 % of the air parcels arriving in the sub-cloud layer have spent at least one day in the extratropics (north of 35° N) before arriving in the eastern Caribbean at about 13° N. In 2018, this share of air parcels with extratropical origin was anomalously large with 88 %. In two detailed case studies during the campaign, two flow regimes with distinct isotope signatures transporting extratropical air into the Caribbean are investigated. In both regimes, the air parcels descend from the lower part of the midlatitude jet stream towards the equator, at the eastern edge of subtropical anticyclones, in the context of Rossby wave breaking events. The zonal location of the wave breaking, and the surface anticyclone, determines the dominant transport regime. The first regime represents the typical trade wind situation with easterly winds bringing moist air from the eastern North Atlantic into the Caribbean, in a deep layer from the surface up to ∼600 hPa. The moisture source of the sub-cloud layer water vapour is located on average 2000 km upstream of Barbados. In this regime, Rossby wave breaking and the descent of air from the extratropics occurs in the eastern North Atlantic, at about 33° W. The second regime is associated with air parcels descending slantwise by on average 300 hPa (6 d)-1 directly from the northeast, i.e., at about 50° W. These originally dry airstreams experience a more rapid moistening than typical trade wind air parcels when interacting with the subtropical oceanic boundary layer, with moisture sources being located on average 1350 km upstream to the northeast of Barbados. The descent of dry air in the second regime can be steered towards the Caribbean by the interplay of a persistent upper-level cutoff low over the central North Atlantic (about 45° W) and the associated surface cyclone underneath. The zonal location of Rossby wave breaking, and consequently, the pathway of extratropical air towards the Caribbean, is shown to be relevant for the sub-cloud layer humidity and shallow cumulus cloud cover properties of the North Atlantic winter trades. Overall, this study highlights the importance of extratropical dynamical processes for the tropical water cycle and reveals that these processes lead to a substantial modulation of stable water isotope signals in the near-surface humidity.

show abstract

Assessing the Sampling Quality of a Low-Tech Low-Budget Volume-Based Rainfall Sampler for Stable Isotope Analysis

Cited by 8 publications

References 28 publications

How Rossby wave breaking modulates the water cycle in the North Atlantic trade wind region

How Rossby wave breaking modulates the water cycle in the North Atlantic trade wind region

Do stream water solute concentrations reflect when connectivity occurs in a small, pre-Alpine headwater catchment?

How Rossby wave breaking modulates the water cycle in the North Atlantic trade wind region

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