MEASUREMENTS OF STRATOSPHERIC WATER VAPOR USING A FROST-POINT HYGROMETER

Abstract. Balloon-borne frost point hygrometers (FPs) and the Aura Microwave Limb Sounder (MLS) provide high-quality vertical profile measurements of water vapor in the upper troposphere and lower stratosphere (UTLS). A previous comparison of stratospheric water vapor measurements by FPs and MLS over three FP sites, Boulder, Colorado (40.0° N), Hilo, Hawaii (19.7° N) and Lauder, New Zealand (45.0° S), from August 2004 through December 2012, demonstrated agreement better than 1 % between 68 and 26 hPa, but also exposed statistically significant biases of 2 to 10 % at 83 and 100 hPa (Hurst et al., 2014). A simple linear regression analysis of the FPH-MLS differences revealed no significant long-term drifts between the two instruments. Here we extend the drift comparison to mid-2015 and add two FP sites, Lindenberg, Germany (52.2° N) and San José, Costa Rica (10.0° N) that employ FPs of different manufacture and calibration for their water vapor soundings. The extended comparison period reveals that stratospheric FP and MLS measurements over 4 of the 5 sites have diverged at rates of 0.03 to 0.07 ppmv yr−1 (0.6 to 1.5 % yr−1) from ~2010 to mid-2015. These rates are similar in magnitude to the 30-year (1980–2010) average growth rate of stratospheric water vapor (~1 % yr−1) measured by FPs over Boulder (Hurst et al., 2011). By mid-2015, the FP-MLS differences at some sites were large enough to exceed the combined accuracy estimates of the FP and MLS measurements.

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An update on the uncertainties of water vapor measurements using cryogenic frost point hygrometers

Atmospheric Measurement Techniques ◽

10.5194/amt-9-3755-2016 ◽

2016 ◽

Vol 9 (8) ◽

pp. 3755-3768 ◽

Cited By ~ 19

Author(s):

Holger Vömel ◽

Tatjana Naebert ◽

Ruud Dirksen ◽

Michael Sommer

Keyword(s):

Water Vapor ◽

Lower Troposphere ◽

Dew Point ◽

Data Series ◽

Mixing Ratio ◽

Stratospheric Water Vapor ◽

Frost Point ◽

Tropical Tropopause ◽

The Impact

Abstract. Long time series of observations of essential climate variables in the troposphere and stratosphere are often impacted by inconsistencies in instrumentation and ambiguities in the interpretation of the data. To reduce these problems of long-term data series, all measurements should include an estimate of their uncertainty and a description of their sources. Here we present an update of the uncertainties for tropospheric and stratospheric water vapor observations using the cryogenic frost point hygrometer (CFH). The largest source of measurement uncertainty is the controller stability, which is discussed here in detail. We describe a method to quantify this uncertainty for each profile based on the measurements. We also show the importance of a manufacturer-independent ground check, which is an essential tool to continuously monitor the uncertainty introduced by instrument variability. A small bias, which has previously been indicated in lower tropospheric measurements, is described here in detail and has been rectified. Under good conditions, the total from all sources of uncertainty of frost point or dew point measurements using the CFH can be better than 0.2 K. Systematic errors, which are most likely to impact long-term climate series, are verified to be less than 0.1 K. The impact of the radiosonde pressure uncertainty on the mixing ratio for properly processed radiosondes is considered small. The mixing ratio uncertainty may be as low as 2 to 3 %. The impact of the ambient temperature uncertainty on relative humidity (RH) is generally larger than that of the frost point uncertainty. The relative RH uncertainty may be as low as 2 % in the lower troposphere and 5 % in the tropical tropopause region.

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Variability of Stratospheric Water Vapor Inferred from SAGE II, HALOE, and Boulder (Colorado) Balloon Measurements

Journal of Climate ◽

10.1175/jcli3841.1 ◽

2006 ◽

Vol 19 (16) ◽

pp. 4121-4133 ◽

Cited By ~ 5

Author(s):

E. W. Chiou ◽

L. W. Thomason ◽

W. P. Chu

Keyword(s):

Water Vapor ◽

Correlation Coefficients ◽

Quantitative Agreement ◽

Stratospheric Aerosol ◽

Stratospheric Water Vapor ◽

Mixing Ratios ◽

Frost Point ◽

The North ◽

Low Latitudes ◽

Balloon Measurements

Abstract The variability of stratospheric water vapor between 1996 and 2004 has been studied using multiyear measurements from the Stratospheric Aerosol and Gas Experiment II (SAGE II) version 6.2 dataset, the Halogen Occultation Experiment (HALOE) version 19 dataset, and the balloon-borne frost point hygrometer data record at Boulder, Colorado (40°N, 105°W). The features derived from SAGE II and HALOE for 20° latitudinal zones from 60°S to 60°N at various altitudes (16–34 km) show good quantitative agreement regarding the phases and magnitudes of annual, semiannual, and quasi-biennial oscillations (QBO). For the latitudinal zones 20°–40° and 40°–60°, the hemispheric asymmetry at 22 km with mainly QBO in the north and predominantly annual oscillations in the south has been revealed by both SAGE II and HALOE observations. Strong correlation exists between SAGE II and HALOE lower-stratospheric H2O anomalies over low latitudes and 100-hPa tropical zonal mean temperature anomalies. The correlation coefficients based on the 0°–20°S water vapor time series with H2O lagged by 2 months are 0.81 and 0.70 for HALOE and SAGE II, respectively. For 35°–45°N, SAGE II and HALOE show consistent trends generally varying from −0.05 to −0.02 ppmv yr−1 between 16 and 34 km. The corresponding analyses based on frost point measurements over Boulder show insignificant trends. These trends are not strongly dependent on the end points of the analysis and stand in contrast to the positive trends reported in previous studies that include data records prior to 1994. For the lower stratosphere, investigations of the entire balloon-borne dataset over Boulder indicate higher values of mixing ratios after 1992–93 compared to the period 1980–92. In contrast, SAGE II monthly zonal mean measurements for 35°–45°N show insignificant differences between the periods 1987–89 and 1996–2004.

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Two-year operation of the lidar1200: from fine-scale tropospheric structures to lower stratospheric water vapor detection

EPJ Web of Conferences ◽

10.1051/epjconf/201817605015 ◽

2018 ◽

Vol 176 ◽

pp. 05015

Author(s):

Hélène Vérèmes ◽

Guillaume Payen ◽

Philippe Keckhut ◽

Valentin Duflot ◽

Jean-Luc Baray ◽

...

Keyword(s):

Water Vapor ◽

Lower Stratosphere ◽

Integration Time ◽

Fine Scale ◽

Vertical Resolution ◽

Vapor Detection ◽

Stratospheric Water Vapor ◽

Frost Point ◽

Time Period ◽

Water Vapor Detection

The 2-year lidar water vapor database (November 2013 - October 2015) of the Maïdo Observatory (Reunion Island / 21°S,55.5°E) is now processed. The performances of the lidar in providing accurate vertical structures are shown to be good. The ability to measure quantities of a few ppmv in the lower stratosphere is demonstrated (based on Cryogenic Frost point Hygrometer sonde/lidar profiles comparisons) for a 48-hour integration time period, up to 22 km (with a vertical resolution of 1.3 km).

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Recent divergences in stratospheric water vapor measurements by frost point hygrometers and the Aura Microwave Limb Sounder

Atmospheric Measurement Techniques ◽

10.5194/amt-9-4447-2016 ◽

2016 ◽

Vol 9 (9) ◽

pp. 4447-4457 ◽

Cited By ~ 14

Author(s):

Dale F. Hurst ◽

William G. Read ◽

Holger Vömel ◽

Henry B. Selkirk ◽

Karen H. Rosenlof ◽

...

Keyword(s):

Water Vapor ◽

Linear Regression Analysis ◽

San Jose ◽

Average Growth ◽

Upper Troposphere ◽

Stratospheric Water Vapor ◽

Frost Point ◽

Comparison Period ◽

Better Than

Abstract. Balloon-borne frost point hygrometers (FPs) and the Aura Microwave Limb Sounder (MLS) provide high-quality vertical profile measurements of water vapor in the upper troposphere and lower stratosphere (UTLS). A previous comparison of stratospheric water vapor measurements by FPs and MLS over three sites – Boulder, Colorado (40.0° N); Hilo, Hawaii (19.7° N); and Lauder, New Zealand (45.0° S) – from August 2004 through December 2012 not only demonstrated agreement better than 1 % between 68 and 26 hPa but also exposed statistically significant biases of 2 to 10 % at 83 and 100 hPa (Hurst et al., 2014). A simple linear regression analysis of the FP–MLS differences revealed no significant long-term drifts between the two instruments. Here we extend the drift comparison to mid-2015 and add two FP sites – Lindenberg, Germany (52.2° N), and San José, Costa Rica (10.0° N) – that employ FPs of different manufacture and calibration for their water vapor soundings. The extended comparison period reveals that stratospheric FP and MLS measurements over four of the five sites have diverged at rates of 0.03 to 0.07 ppmv year−1 (0.6 to 1.5 % year−1) from ∼  2010 to mid-2015. These rates are similar in magnitude to the 30-year (1980–2010) average growth rate of stratospheric water vapor ( ∼  1 % year−1) measured by FPs over Boulder (Hurst et al., 2011). By mid-2015, the FP–MLS differences at some sites were large enough to exceed the combined accuracy estimates of the FP and MLS measurements.

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Intercomparisons of Stratospheric Water Vapor Sensors: FLASH-B and NOAA/CMDL Frost-Point Hygrometer

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech2007.1 ◽

2007 ◽

Vol 24 (6) ◽

pp. 941-952 ◽

Cited By ~ 34

Author(s):

H. Vömel ◽

V. Yushkov ◽

S. Khaykin ◽

L. Korshunov ◽

E. Kyrö ◽

...

Keyword(s):

Water Vapor ◽

Global Climate ◽

Time Lag ◽

The Arctic ◽

Mean Deviation ◽

Upper Troposphere ◽

Stratospheric Water Vapor ◽

Frost Point ◽

Dry Conditions ◽

Monitoring And Diagnostics

Studies of global climate rely critically on accurate water vapor measurements. In this paper, a comparison of the NOAA/Climate Monitoring and Diagnostics Laboratory (CMDL) frost-point hygrometer and the Fluorescent Advanced Stratospheric Hygrometer for Balloon (FLASH-B) Lyman-alpha hygrometer is reported. Both instruments were part of a small balloon payload that was launched multiple times at Sodankylä, Finland. The comparison shows agreement well within the instrumental uncertainties between both sensors in the Arctic stratospheric vortex. The mean deviation between both instruments in the range between 15 and 25 km is −2.4% ± 3.1% (one standard deviation). The comparison identified some instrumental issues, such as a low mirror-temperature calibration correction for the NOAA/CMDL frost-point hygrometer as well as a time lag. It was found that the FLASH-B hygrometer measures water vapor reliably above 7 km in the polar atmosphere. Comparisons in the upper troposphere are affected by the gain change of the NOAA/CMDL hygrometer, causing a lag and a wet bias in the tropospheric low gain setting under the dry conditions in the upper troposphere.

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Advancements, measurement uncertainties, and recent comparisons of the NOAA frost point hygrometer

Atmospheric Measurement Techniques ◽

10.5194/amt-9-4295-2016 ◽

2016 ◽

Vol 9 (9) ◽

pp. 4295-4310 ◽

Cited By ~ 10

Author(s):

Emrys G. Hall ◽

Allen F. Jordan ◽

Dale F. Hurst ◽

Samuel J. Oltmans ◽

Holger Vömel ◽

...

Keyword(s):

Water Vapor ◽

Full Range ◽

Dew Point ◽

Tunable Diode Laser ◽

Stratospheric Water Vapor ◽

Laser Absorption ◽

Frost Point ◽

High Level ◽

Diode Laser Absorption ◽

Good Agreement

Abstract. The NOAA frost point hygrometer (FPH) is a balloon-borne instrument flown monthly at three sites to measure water vapor profiles up to 28 km. The FPH record from Boulder, Colorado, is the longest continuous stratospheric water vapor record. The instrument has an uncertainty in the stratosphere that is <  6 % and up to 12 % in the troposphere. A digital microcontroller version of the instrument improved upon the older versions in 2008 with sunlight filtering, better frost control, and resistance to radio frequency interference (RFI). A new thermistor calibration technique was implemented in 2014, decreasing the uncertainty in the thermistor calibration fit to less than 0.01 °C over the full range of frost – or dew point temperatures (−93 to +20 °C) measured during a profile. Results from multiple water vapor intercomparisons are presented, including the excellent agreement between the NOAA FPH and the direct tunable diode laser absorption spectrometer (dTDLAS) MC-PicT-1.4 during AquaVIT-2 chamber experiments over 6 days that provides confidence in the accuracy of the FPH measurements. Dual instrument flights with two FPHs or an FPH and a cryogenic frost point hygrometer (CFH) also show good agreement when launched on the same balloon. The results from these comparisons demonstrate the high level of accuracy of the NOAA FPH.

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