Review of "Characterising water vapour concentration dependence of commercial cavity ring-down spectrometers for continuous onsite atmospheric water vapour isotope measurements in the tropics" by Komiya et al.

Commercially available laser-based spectrometers permit continuous field measurements of water vapour (H2O) stable isotope compositions, yet continuous observations in the Amazon, a region that significantly influences atmospheric hydrological cycles on regional to global scales, are largely missing. In order to achieve accurate on-site observations in such conditions, these instruments will require regular on-site calibration, including for H2O concentration dependence ([H2O]-dependence) of isotopic accuracy.With the aim of conducting accurate continuous &#948;18O and &#948;2H on-site observation in the Amazon rainforest, we conducted a laboratory experiment to investigate the performance and determine the optimal [H2O]-dependence calibration strategy for two commercial cavity-ring down (CRDS) analysers (L1102i and L2130i models, Picarro, Inc., USA), coupled to our custom-built automated calibration unit. We particularly focused on the rarely investigated performance of the instruments at atmospheric H2O contents above 35,000 ppm, a value regularly reached at our site.The later analyser model (L2130i) had better precision and accuracy of &#948;18O and &#948;2H measurements with a less pronounced [H2O]-dependence compared to the older L1102i. The [H2O]-dependence calibration uncertainties did not significantly change with calibration intervals from 28 h up to 196 h, suggesting that one [H2O]-dependence calibration per week for the L2130i and L1102i analysers is enough. This study shows that with both CRDS analysers, correctly calibrated, we should be able to discriminate natural diel, seasonal and interannual signals of stable water vapour isotopes in a tropical rainforest environment.&#160;

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Characterising water vapour concentration dependence of commercial cavity ring-down spectrometers for continuous onsite atmospheric water vapour isotope measurements in the tropics

10.5194/amt-2020-305 ◽

2020 ◽

Author(s):

Shujiro Komiya ◽

Fumiyoshi Kondo ◽

Heiko Moossen ◽

Thomas Seifert ◽

Uwe Schultz ◽

...

Keyword(s):

Water Vapour ◽

Concentration Dependence ◽

Water Vapour Concentration ◽

Fitting Method ◽

Vapour Concentration ◽

In Situ Calibration ◽

Significant Difference ◽

Hydrological Cycles ◽

The Tropics

Abstract. The recent development and improvement of commercial laser-based spectrometers have expanded in situ continuous observations of water vapour (H2O) stable isotope ratios (e.g., δ18O, δ2H, etc.) in a variety of sites worldwide. However, we still lack continuous observations in the Amazon, a region that significantly influences atmospheric and hydrological cycles on local to global scales. In order to achieve accurate on-site observations, commercial water isotope analysers require regular in situ calibration, including H2O concentration dependence ([H2O]-dependence) of isotopic accuracy. Past studies have assessed [H2O]-dependence for air with H2O concentrations up to 35,000 ppm, a value that is frequently surpassed in tropical rainforest settings like the central Amazon where we plan continuous observations. Here we investigated the performance of two commercial analysers (L1102i and L2130i models, Picarro, Inc., USA) for measuring δ18O and δ2H in atmospheric moisture at four different H2O levels from 21,500 to 41,000 ppm. These H2O levels were created by a custom-built calibration unit designed for regular in situ calibration. Measurements on the newer analyser model (L2130i) had better precision for δ18O and δ2H and demonstrated less influence of H2O concentration on the measurement accuracy at each moisture level compared to the older L1102i. Based on our findings, we identified the most appropriate calibration strategy for [H2O]-dependence, adapted to our calibration system. The best strategy required using two pairs of a two-point calibration with four different H2O concentration levels. The smallest uncertainties in calibrating [H2O]-dependence of isotopic accuracy of the two analysers were achieved using a linear-surface fitting method and a 28 h calibration interval, except for the δ18O accuracy of the L1102i analyser for which the cubic fitting method gave best results. The uncertainties in [H2O]-dependence calibration did not show any significant difference using calibration intervals from 28 h up to 196 h; this suggested that one [H2O]-dependence calibration per week for the L2130i and L1102i analysers is sufficient.

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Variability of atmospheric water-vapour concentration and its implications for microwave-radio-link planning

Electronics Letters ◽

10.1049/el:19770463 ◽

1977 ◽

Vol 13 (21) ◽

pp. 650

Author(s):

M.P.M. Hall

Keyword(s):

Water Vapour ◽

Radio Link ◽

Atmospheric Water ◽

Atmospheric Water Vapour ◽

Water Vapour Concentration ◽

Vapour Concentration ◽

Microwave Radio

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An annual cycle of long lived stratospheric gases from MIPAS

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-1879-2007 ◽

2007 ◽

Vol 7 (7) ◽

pp. 1879-1897 ◽

Cited By ~ 11

Author(s):

M. N. Juckes

Keyword(s):

Standard Deviation ◽

Water Vapour ◽

Polar Regions ◽

Upward Motion ◽

High Quality ◽

Height Range ◽

Water Vapour Concentration ◽

Vapour Concentration ◽

Using Data ◽

The Tropics

Abstract. MIPAS, on ENVISAT, has made high quality observations of ozone, methane and water vapour. Gridded fields, at 4 hourly intervals and, have been calculated for all of 2003 using data assimilation with isentropic advection as a constraint. The gridded fields are validated against independent measurements (from 7 other instruments in the case of ozone, 3 for water vapour and one for methane). For ozone the results are in agreement with previously published results. For water vapour the bias relative to HALOE is below 10% between 20 and 48 km, and the standard deviation is below 12% in this range. Departures from SAGE II and POAM III are substantially larger. The methane analysis has a bias of less than 5% relative to HALOE between 23 and 40 km, with a standard deviation less than 10% in this height range. The water vapour field clearly reflects the upward motion in the lower tropical stratosphere, while both water vapour and methane show the signature of advection higher up. In the polar regions the descent in the vortex is clearly visible, with strong descent in autumn giving way to weaker descent through the winter. Descent rates of around 10−3ms−1 are found during the formation of the polar vortices, slowing to around 3×10−4ms−1 during the winter. Ascent of around 2×10−4ms−1 in the tropics is revealed by the water vapour and total observed hydrogen fields (4 times the methane plus twice the water vapour concentration). The total observed hydrogen is depleted in the polar upper stratosphere when air is advected down from the upper mesosphere.

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An annual cycle of long lived stratospheric gases from MIPAS

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-6-9389-2006 ◽

2006 ◽

Vol 6 (5) ◽

pp. 9389-9429 ◽

Cited By ~ 1

Author(s):

M. N. Juckes

Keyword(s):

Water Vapour ◽

Standard Error ◽

Polar Regions ◽

Upward Motion ◽

High Quality ◽

Height Range ◽

Water Vapour Concentration ◽

Vapour Concentration ◽

Using Data ◽

The Tropics

Abstract. MIPAS, on ENVISAT, has made high quality observations of ozone, methane and water vapour. Gridded fields, at 4 hourly intervals and approximately 2 degree resolution, have been calculated for all of 2003 using data assimilation with isentropic advection as a constraint. The gridded fields are validated against independent measurements (from 7 other instruments in the case of ozone, 3 for water vapour and one for methane). For ozone the results are in agreement with previously published results. For water vapour the bias relative to HALOE is below 10% between 20 and 48 km, and the standard error is below 12% in this range. Departures from SAGE II and POAM III are substantially larger. The methane analysis has a bias of less than 5% relative to HALOE between 23 and 40 km, with a standard error less than 10% in this height range. The water vapour field clearly reflects the upward motion in the lower tropical stratosphere, while both water vapour and methane show the signature of advection higher up. In the polar regions the descent in the vortex is clearly visible, with strong descent in autumn giving way to weaker descent through the winter. Descent rates of around 100 m/day are found during the formation of the polar vortices, slowing to around 30 m/day during the winter. Ascent of around 20 m/day in the tropics is revealed by the water vapour and total observed hydrogen fields (4 times the methane plus twice the water vapour concentration). The total observed hydrogen is depleted where air is advected down from the upper mesosphere.

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Characterizing water vapour concentration dependence of commercial cavity ring-down spectrometers for continuous on-site atmospheric water vapour isotope measurements in the tropics

Atmospheric Measurement Techniques ◽

10.5194/amt-14-1439-2021 ◽

2021 ◽

Vol 14 (2) ◽

pp. 1439-1455

Author(s):

Shujiro Komiya ◽

Fumiyoshi Kondo ◽

Heiko Moossen ◽

Thomas Seifert ◽

Uwe Schultz ◽

...

Keyword(s):

Water Vapour ◽

Concentration Dependence ◽

Central Amazon ◽

Water Vapour Concentration ◽

Fitting Method ◽

In Situ Calibration ◽

Significant Difference ◽

Calibration Interval ◽

Cavity Ring Down

Abstract. The recent development and improvement of commercial laser-based spectrometers have expanded in situ continuous observations of water vapour (H2O) stable isotope compositions (e.g. δ18O and δ2H) in a variety of sites worldwide. However, we still lack continuous observations in the Amazon, a region that significantly influences atmospheric and hydrological cycles on local to global scales. In order to achieve accurate on-site observations, commercial water isotope analysers require regular in situ calibration, which includes the correction of H2O concentration dependence ([H2O] dependence) of isotopic measurements. Past studies have assessed the [H2O] dependence for air with H2O concentrations of up to 35 000 ppm, a value that is frequently surpassed in tropical rainforest settings like the central Amazon where we plan continuous observations. Here we investigated the performance of two commercial analysers (L1102i and L2130i models, Picarro, Inc., USA) for measuring δ18O and δ2H in atmospheric moisture at four different H2O levels from 21 500 to 41 000 ppm. These H2O levels were created by a custom-built calibration unit designed for regular in situ calibration. Measurements on the newer analyser model (L2130i) had better precision for δ18O and δ2H and demonstrated less influence of H2O concentration on the measurement accuracy at each concentration level compared to the older L1102i. Based on our findings, we identified the most appropriate calibration strategy for [H2O] dependence, adapted to our calibration system. The best strategy required conducting a two-point calibration with four different H2O concentration levels, carried out at the beginning and end of the calibration interval. The smallest uncertainties in calibrating [H2O] dependence of isotopic accuracy of the two analysers were achieved using a linear surface fitting method and a 28 h calibration interval, except for the δ18O accuracy of the L1102i analyser for which the cubic fitting method gave the best results. The uncertainties in [H2O] dependence calibration did not show any significant difference using calibration intervals from 28 up to 196 h; this suggested that one [H2O] dependence calibration per week for the L2130i and L1102i analysers is sufficient. This study shows that the cavity ring-down spectroscopy (CRDS) analysers, appropriately calibrated for [H2O] dependence, allow the detection of natural signals of stable water vapour isotopes at very high humidity levels, which has promising implications for water cycle studies in areas like the central Amazon rainforest and other tropical regions.

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Atmospheric water vapour processing

Waterlines ◽

10.3362/0262-8104.1993.039 ◽

1993 ◽

Vol 12 (2) ◽

pp. 20-22 ◽

Cited By ~ 3

Author(s):

Roland Wahlgren

Keyword(s):

Water Vapour ◽

Atmospheric Water ◽

Atmospheric Water Vapour

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