Open‐path, near‐infrared tunable diode laser spectrometer for atmospheric measurements of H<sub>2</sub>O

May, R. D.

doi:10.1029/98jd01678

Cited by 149 publications

(151 citation statements)

References 34 publications

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“…In addition, several studies have used simple numerical models to simulate the propagation and attenuation of the H20 and CO2 seasonal signals. These studies typically assume that the amplitude of the seasonal signal at midlatitude is zero, which is not consistent with our observations (Figure 4) [May, 1998] to better than 5%, with agreement best near ER-2 cruise altitudes at ambient pressures for which the diode laser spectrometer was optimized. Indirect comparisons can also be made with instruments that have produced data sets from which annually averaged entry-level water vapor mixing ratios in air entering the stratosphere can be derived.…”

Section: The Best Fit Between (C02)mbc and (Co2)• Was Determined By Vcontrasting

confidence: 46%

Constraints on the seasonal cycle of stratospheric water vapor using in situ measurements from the ER‐2 and a CO photochemical clock

Weinstock¹,

Hintsa²,

Kirk-Davidoff³

et al. 2001

J. Geophys. Res.

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Abstract. We use in situ measurements of CO obtained in the tropics from 1995 to 1997 on the NASA ER-2 aircraft and a simple photochemical model to calculate the elapsed time between the entry of air into the stratosphere and the observation, which we define as the photochemical "age" of the air. Assuming this age represents the transit time of the air mass from a boundary at 390 K to its measured altitude, we calculate boundary condition values of CO2 derived from in situ measurements of this species from 400 to 480 K. We validate the approach by comparing these CO2 boundary values with an independent representation of the boundary condition from observations of CO• in air that had recently entered the stratosphere (as indicated by simultaneous measurements of N20, CO, and potential temperature). For five of the six flights, differences between CO• boundary condition values determined using the photochemical age of the air and those derived from independent measurements can be accounted for with isentropic mixing of midlatitude stratospheric air into the tropics. Having validated the photochemical ages of the sampled stratospheric air, we use the same analysis of in situ water data to provide water vapor boundary condition values that constrain the seasonal cycle of water vapor entering the stratosphere. On the basis of these constraints we evaluate the seasonal cycle of entry-level water vapor derived from tropical tropopause temperatures from the radiosonde network between 10øS and 10øN. We conclude that while average saturation mixing ratios provide a suitable boundary condition for water vapor entering the stratosphere, the uncertainties in saturation mixing ratios derived from radiosonde temperatures and the lack of coverage prevents distinguishing between ascent preferentially occurring over the western equatorial Pacific or throughout the tropics. With the assumption that vertical diffusion and midlatitude mixing have a negligible effect on the calculated age, ascent velocities can be inferred from the photochemical ages. These ascent velocities show a seasonal cycle that is inconsistent with our current understanding of the dynamics driving the stratospheric circulation and with independent estimates of tropical vertical ascent rates.

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Section: The Best Fit Between (C02)mbc and (Co2)• Was Determined By Vcontrasting

confidence: 46%

Constraints on the seasonal cycle of stratospheric water vapor using in situ measurements from the ER‐2 and a CO photochemical clock

Weinstock¹,

Hintsa²,

Kirk-Davidoff³

et al. 2001

J. Geophys. Res.

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“…During the POLARIS mission (April-September 1997), we compared our instrument with a new tunable diode laser (TDL) hygrometer from the Jet Propulsion Laboratory (JPL) [May, 1998]. The JPL instrument is an open-path spectrometer operating near 1.37 #m, mounted below the right wing superpod on the ER-2 during POLARIS.…”

Section: Intercomparison With the Jpl Hygrometermentioning

confidence: 99%

On the accuracy of in situ water vapor measurements in the troposphere and lower stratosphere with the Harvard Lyman‐α hygrometer

Hintsa¹,

Weinstock²,

Anderson³

et al. 1999

J. Geophys. Res.

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Abstract. In an effort to better constrain atmospheric water vapor mixing ratios and to understand the discrepancies between different measurements of water vapor in the stratosphere and troposphere, we have carefully examined data from the Harvard Lyman-tz photofragment fluorescence hygrometer, which has flown on the NASA ER-2 aircraft from 1992 through 1998. The instrument is calibrated in the laboratory before and after each deployment, and the calibration is checked by direct absorption measurements in the troposphere. On certain flights, the ER-2 flew level tracks during which water vapor varied by up to 80 ppmv, under nearly constant atmospheric conditions, These flights provide a stringent test of our calibration via direct absorption and indicate agreement to within 3%. During the 1997 Photochemistry of Ozone Loss in the Arctic Region In Summer (POLARIS) mission, our Lyman-tz instrument was compared with a new diode laser hygrometer from the Jet Propulsion Laboratory. Overall agreement was 5% during the June/July deployment and 1 øk for potential temperatures of 490 to 540 K. The accuracy of our instrument is shown to be _+5%, with an additional offset of at most 0.1 ppmv. Data from this instrument, combined with simultaneous measurements of CH4 and H2, are therefore ideal for studies of the hydrogen budget of the lower stratosphere.

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“…Over the last decades, numerous hygrometers were developed and deployed on aircraft (Busen and Buck, 1995;Cerni, 1994;Desjardins et al, 1989;Diskin et al, 2002;Durry et al, 2008;Ebert et al, 2000;Gurlit et al, 2005;Hansford et al, 2006;Helten et al, 1998;Hunsmann et al, 2008;Karpechko et al, 2014;Kley and Stone, 1978;May, 1998;Meyer et al, 2015;Ohtaki and Matsui, 1982;Roths and Busen, 1996;Salasmaa and Kostamo, 1986;Schiff et al, 1994;Silver and Hovde, 1994b, a;Thornberry et al, 2015;Webster et al, 2004;Zöger et al, 1999a, b) (non-exhaustive list). While for some atmospheric questions the quality level of the data often is sufficient (e.g., typically climatologies), there are also a variety of questions, especially validation of atmospheric models, where the required absolute accuracy, precision, temporal resolution, long-term stability, comparability, etc.…”

Section: Introductionmentioning

confidence: 99%

Absolute, pressure-dependent validation of a calibration-free, airborne laser hygrometer transfer standard (SEALDH-II) from 5 to 1200 ppmv using a metrological humidity generator

Buchholz

Ebert

2018

Atmos. Meas. Tech.

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Abstract. Highly accurate water vapor measurements are indispensable for understanding a variety of scientific questions as well as industrial processes. While in metrology water vapor concentrations can be defined, generated, and measured with relative uncertainties in the single percentage range, field-deployable airborne instruments deviate even under quasistatic laboratory conditions up to 10–20 %. The novel SEALDH-II hygrometer, a calibration-free, tuneable diode laser spectrometer, bridges this gap by implementing a new holistic concept to achieve higher accuracy levels in the field. We present in this paper the absolute validation of SEALDH-II at a traceable humidity generator during 23 days of permanent operation at 15 different H2O mole fraction levels between 5 and 1200 ppmv. At each mole fraction level, we studied the pressure dependence at six different gas pressures between 65 and 950 hPa. Further, we describe the setup for this metrological validation, the challenges to overcome when assessing water vapor measurements on a high accuracy level, and the comparison results. With this validation, SEALDH-II is the first airborne, metrologically validated humidity transfer standard which links several scientific airborne and laboratory measurement campaigns to the international metrological water vapor scale.

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Open‐path, near‐infrared tunable diode laser spectrometer for atmospheric measurements of H₂O

Cited by 149 publications

References 34 publications

Constraints on the seasonal cycle of stratospheric water vapor using in situ measurements from the ER‐2 and a CO photochemical clock

Constraints on the seasonal cycle of stratospheric water vapor using in situ measurements from the ER‐2 and a CO photochemical clock

On the accuracy of in situ water vapor measurements in the troposphere and lower stratosphere with the Harvard Lyman‐α hygrometer

Absolute, pressure-dependent validation of a calibration-free, airborne laser hygrometer transfer standard (SEALDH-II) from 5 to 1200 ppmv using a metrological humidity generator

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Open‐path, near‐infrared tunable diode laser spectrometer for atmospheric measurements of H2O

Cited by 149 publications

References 34 publications

Constraints on the seasonal cycle of stratospheric water vapor using in situ measurements from the ER‐2 and a CO photochemical clock

Constraints on the seasonal cycle of stratospheric water vapor using in situ measurements from the ER‐2 and a CO photochemical clock

On the accuracy of in situ water vapor measurements in the troposphere and lower stratosphere with the Harvard Lyman‐α hygrometer

Absolute, pressure-dependent validation of a calibration-free, airborne laser hygrometer transfer standard (SEALDH-II) from 5 to 1200 ppmv using a metrological humidity generator

Contact Info

Product

Resources

About

Open‐path, near‐infrared tunable diode laser spectrometer for atmospheric measurements of H₂O