Comments on “Accuracy of Raman lidar water vapor calibration and its applicability to long-term measurements”

Abstract. We have investigated calibration variations in the Rameau water vapor Raman lidar. This lidar system was developed by the Institut National de l'Information Géographique et Forestière (IGN) together with the Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS). It aims at calibrating Global Navigation Satellite System (GNSS) measurements for tropospheric wet delays and sounding the water vapor variability in the lower troposphere. The Rameau system demonstrated good capacity in retrieving water vapor mixing ratio (WVMR) profiles accurately in several campaigns. However, systematic short-term and long-term variations in the lidar calibration factor pointed to persistent instabilities. A careful testing of each subsystem independently revealed that these instabilities are mainly induced by mode fluctuations in the optic fiber used to couple the telescope to the detection subsystem and by the spatial nonuniformity of the photomultiplier photocathodes. Laboratory tests that replicate and quantify these instability sources are presented. A redesign of the detection subsystem is presented, which, combined with careful alignment procedures, is shown to significantly reduce the instabilities. Outdoor measurements were performed over a period of 5 months to check the stability of the modified lidar system. The calibration changes in the detection subsystem were monitored with lidar profile measurements using a common nitrogen filter in both Raman channels. A short-term stability of 2–3 % and a long-term drift of 2–3 % per month are demonstrated. Compared to the earlier Development of Methodologies for Water Vapour Measurement (DEMEVAP) campaign, this is a 3-fold improvement in the long-term stability of the detection subsystem. The overall water vapor calibration factors were determined and monitored with capacitive humidity sensor measurements and with GPS zenith wet delay (ZWD) data. The changes in the water vapor calibration factors are shown to be fairly consistent with the changes in the nitrogen calibration factors. The nitrogen calibration results can be used to correct the overall calibration factors without the need for additional water vapor measurements to within 1 % per month.

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A Raman lidar at La Reunion (20.8° S, 55.5° E) for monitoring water vapor and cirrus distributions in the subtropical upper troposphere: preliminary analyses and description of a future system

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-4-6449-2011 ◽

2011 ◽

Vol 4 (5) ◽

pp. 6449-6496

Author(s):

C. Hoareau ◽

P. Keckhut ◽

J.-L. Baray ◽

L. Robert ◽

Y. Courcoux ◽

...

Keyword(s):

Water Vapor ◽

Cirrus Cloud ◽

La Réunion ◽

Raman Lidar ◽

Data Set ◽

Upper Troposphere ◽

Future System ◽

Rayleigh Lidar ◽

Term Monitoring

Abstract. A ground based Rayleigh lidar has provided continuous observations of tropospheric water vapor profiles and cirrus cloud using a preliminary Raman channels setup on an existing Rayleigh lidar above La Reunion over the period 2002–2005. With this instrument, we performed a first measurement campaign of 350 independent water vapor profiles. A statistical study of the distribution of water vapor profiles is presented and some investigations concerning the calibration are discussed. The data set having several long acquisition measurements during nighttime, an analysis of the diurnal cycle of water vapor has also been investigated. Analysis regarding the cirrus clouds is presented and a classification has been performed showing 3 distinct classes. Based on these results, the characteristics and the design of a future lidar system to be implemented at the new Reunion Island altitude observatory (2200 m) for long-term monitoring is presented and numerical simulations of system performance have been realized to compare both instruments.

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Ground-based water vapor raman lidar measurements up to the upper troposphere and lower stratosphere for long-term monitoring

Atmospheric Measurement Techniques ◽

10.5194/amt-5-17-2012 ◽

2012 ◽

Vol 5 (1) ◽

pp. 17-36 ◽

Cited By ~ 43

Author(s):

T. Leblanc ◽

I. S. McDermid ◽

T. D. Walsh

Keyword(s):

Water Vapor ◽

Lower Stratosphere ◽

Lower Troposphere ◽

Atmospheric Composition ◽

Raman Lidar ◽

Upper Troposphere ◽

Lidar Measurements ◽

Development Data ◽

Instrumental Development

Abstract. Recognizing the importance of water vapor in the upper troposphere and lower stratosphere (UTLS) and the scarcity of high-quality, long-term measurements, JPL began the development of a powerful Raman lidar in 2005 to try to meet these needs. This development was endorsed by the Network for the Detection of Atmospheric Composition Change (NDACC) and the validation program for the EOS-Aura satellite. In this paper we review the stages in the instrumental development, data acquisition and analysis, profile retrieval and calibration procedures of the lidar, as well as selected results from three validation campaigns: MOHAVE (Measurements of Humidity in the Atmosphere and Validation Experiments), MOHAVE-II, and MOHAVE 2009. In particular, one critical result from this latest campaign is the very good agreement (well below the reported uncertainties) observed between the lidar and the Cryogenic Frost-Point Hygrometer in the entire lidar range 3–20 km, with a mean bias not exceeding 2% (lidar dry) in the lower troposphere, and 3% (lidar moist) in the UTLS. Ultimately the lidar has demonstrated capability to measure water vapor profiles from ∼1 km above the ground to the lower stratosphere with a precision of 10% or better near 13 km and below, and an estimated accuracy of 5%. Since 2005, nearly 1000 profiles have been routinely measured, and since 2009, the profiles have typically reached 14 km for one-hour integration times and 1.5 km vertical resolution, and can reach 21 km for 6-h integration times using degraded vertical resolutions. These performance figures show that, with our present target of routinely running our lidar two hours per night, 4 nights per week, we can achieve measurements with a precision in the UTLS equivalent to that achieved if launching one CFH per month.

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Accuracy of Raman lidar water vapor calibration and its applicability to long-term measurements

Applied Optics ◽

10.1364/ao.47.005592 ◽

2008 ◽

Vol 47 (30) ◽

pp. 5592 ◽

Cited By ~ 40

Author(s):

Thierry Leblanc ◽

I. Stuart McDermid

Keyword(s):

Water Vapor ◽

Raman Lidar

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Methodology for Water Monitoring in the Upper Troposphere with Raman Lidar at the Haute-Provence Observatory

Journal of Atmospheric and Oceanic Technology ◽

10.1175/2009jtecha1287.1 ◽

2009 ◽

Vol 26 (10) ◽

pp. 2149-2160 ◽

Cited By ~ 18

Author(s):

Christophe Hoareau ◽

Philippe Keckhut ◽

Alain Sarkissian ◽

Jean-Luc Baray ◽

Georges Durry

Keyword(s):

Water Vapor ◽

Time Integration ◽

Raman Lidar ◽

Total Water ◽

Upper Troposphere ◽

Clear Sky ◽

Term Evolution ◽

Calibration Methods ◽

Calibration Techniques

Abstract A Raman water vapor lidar has been developed at the Haute-Provence Observatory to study the distribution of water in the upper troposphere and its long-term evolution. Some investigations have been proposed and described to ensure a pertinent monitoring of water vapor in the upper troposphere. A new method to take into account the geophysical variability for time integration processes has been developed based on the stationarity of water vapor. Successive measurements, considered as independent, have been used to retrieve H2O profiles that were recorded during the same nighttimes over a few hours. Various calibration methods, including zenith clear-sky observation, standard meteorological radiosondes, and total water vapor column, have been investigated. A method to evaluate these calibration techniques has been proposed based on the variance weakening. For the lidar at the Haute-Provence Observatory, the calibration based on the total water vapor column appears to be the optimum method. Radiosondes also give comparable results, but do not allow lidar to be independent. The clear-sky zenith observation is an original technique, and seems to accurately identify discontinuities. However, it appears to be less reliable, based on the variance investigation, than the two others. It is also sensitive to aerosol loading, which is also expected to vary with time.

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Reply to “Comments on Accuracy of Raman lidar water vapor calibration and its applicability to long-term measurements” by Whiteman et al

Applied Optics ◽

10.1364/ao.50.002177 ◽

2011 ◽

Vol 50 (15) ◽

pp. 2177 ◽

Cited By ~ 6

Author(s):

Thierry Leblanc ◽

I. Stuart McDermid

Keyword(s):

Water Vapor ◽

Raman Lidar

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Ground-based water vapor Raman lidar measurements up to the upper troposphere and lower stratosphere – Part 2: Data analysis and calibration for long-term monitoring

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-4-5111-2011 ◽

2011 ◽

Vol 4 (4) ◽

pp. 5111-5145 ◽

Cited By ~ 2

Author(s):

T. Leblanc ◽

I. S. McDermid ◽

T. D. Walsh

Keyword(s):

Water Vapor ◽

Data Analysis ◽

Lower Stratosphere ◽

Companion Paper ◽

Atmospheric Composition ◽

Raman Lidar ◽

Upper Troposphere ◽

Current Configuration ◽

Instrumental Development

Abstract. The well-recognized, key role of water vapor in the upper troposphere and lower stratosphere (UT/LS) and the scarcity of high-quality, long-term measurements triggered the development by JPL of a powerful Raman lidar to try to meet these needs. This development started in 2005 and was endorsed by the Network for the Detection of Atmospheric Composition Change (NDACC) and the validation program for the EOS-Aura satellite. In this paper we review all the stages of the instrument data acquisition, data analysis, profile retrieval and calibration procedures, as well as selected results from the recent validation campaign MOHAVE-2009 (Measurements of Humidity in the Atmosphere and Validation Experiments). The stages in the instrumental development and the conclusions from three validation campaigns (including MOHAVE-2009) are presented in details in a companion paper (McDermid et al., 2011). In its current configuration, the lidar demonstrated capability to measure water vapor profiles from ~1 km above the ground to the lower stratosphere with an estimated accuracy of 5 %. Since 2005, nearly 1000 profiles have been routinely measured with a precision of 10 % or better near 13 km. Since 2009, the profiles have typically reached 14 km for 1 h integration times and 1.5 km vertical resolution, and can reach 21 km for 6-h integration times using degraded vertical resolutions.

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Ground-based water vapor Raman lidar measurements up to the upper troposphere and lower stratosphere – Part 1: Instrument development, optimization, and validation

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-4-5079-2011 ◽

2011 ◽

Vol 4 (4) ◽

pp. 5079-5109 ◽

Cited By ~ 4

Author(s):

I. S. McDermid ◽

T. Leblanc ◽

T. D. Walsh

Keyword(s):

Water Vapor ◽

Lower Stratosphere ◽

Companion Paper ◽

Atmospheric Composition ◽

Raman Lidar ◽

Upper Troposphere ◽

Lidar Measurements ◽

Instrumental Development ◽

Validation Experiments

Abstract. Recognizing the importance of water vapor in the upper troposphere and lower stratosphere (UT/LS) and the scarcity of high-quality, long-term measurements, JPL began the development of a powerful Raman lidar in 2005 to try to meet these needs. This development was endorsed by the Network for the Detection of Atmospheric Composition Change (NDACC) and the validation program for the EOS-Aura satellite. In this paper we review the stages in the instrumental development of the lidar and the conclusions from three validation campaigns: MOHAVE, MOHAVE-II, and MOHAVE 2009 (Measurements of Humidity in the Atmosphere and Validation Experiments). The data analysis, profile retrieval and calibration procedures, as well as additional results from MOHAVE-2009 are presented in detail in a companion paper (Leblanc et al., 2011a). Ultimately the lidar has demonstrated capability to measure water vapor profiles from ~1 km above the ground to the lower stratosphere, reaching 14 km for 1-h integrated profiles and 21 km for 6-h integrated profiles, with a precision of 10 % or better near 13 km and below, and an estimated accuracy of 5 %.

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