Study and mitigation of calibration factor instabilities in a water vapor Raman lidar

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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Lamp mapping technique for independent determination of the water vapor mixing ratio calibration factor for a Raman lidar system

Applied Optics ◽

10.1364/ao.50.004622 ◽

2011 ◽

Vol 50 (23) ◽

pp. 4622 ◽

Cited By ~ 24

Author(s):

Demetrius D. Venable ◽

David N. Whiteman ◽

Monique N. Calhoun ◽

Afusat O. Dirisu ◽

Rasheen M. Connell ◽

...

Keyword(s):

Water Vapor ◽

Calibration Factor ◽

Mapping Technique ◽

Mixing Ratio ◽

Raman Lidar ◽

Lidar System ◽

Independent Determination ◽

Water Vapor Mixing Ratio

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Diffuse sunlight based calibration of the water vapor channel in the upc raman lidar

EPJ Web of Conferences ◽

10.1051/epjconf/201817605035 ◽

2018 ◽

Vol 176 ◽

pp. 05035

Author(s):

Constantino Muñoz-Porcar ◽

Adolfo Comeron ◽

Michaël Sicard ◽

Ruben Barragan ◽

David Garcia-Vizcaino ◽

...

Keyword(s):

Water Vapor ◽

Raman Scattering ◽

Calibration Factor ◽

Raman Lidar ◽

Lidar System ◽

System Parameters ◽

Vapor Channel ◽

Technical University

A method for determining the calibration factor of the water vapor channel of a Raman lidar, based on zenith measurements of diffuse sunlight and on assumptions regarding some system parameters and Raman scattering models, has been applied to the lidar system of Universitat Politècnica de Catalunya (UPC; Technical University of Catalonia, Spain). Results will be analyzed in terms of stability and comparison with typical methods relying on simultaneous radiosonde measurements.

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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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A rubidium frequency standard and a GPS receiver. A remotely steered clock system with good short-term and long-term stability

10.1109/freq.1990.177493 ◽

2002 ◽

Cited By ~ 4

Author(s):

D.W. Allan ◽

J. Levine

Keyword(s):

Frequency Standard ◽

Gps Receiver ◽

Short Term ◽

Term Stability ◽

Long Term Stability ◽

Clock System

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A survey of short-term and long-term stability of tube parameters in a mammography unit

Nuclear Technology and Radiation Protection ◽

10.2298/ntrp1404321p ◽

2014 ◽

Vol 29 (4) ◽

pp. 321-325

Author(s):

Jovica Praskalo ◽

Jasna Davidovic ◽

Biljana Kocic ◽

Monika Zivkovic ◽

Svetlana Pejovic

Keyword(s):

Screening Program ◽

Short Term ◽

X Ray ◽

Term Stability ◽

Long Term Stability ◽

Mammography Screening Program ◽

The Republic ◽

Set Up ◽

The Given

In order to set up a successful mammography screening program in the Republic of Srpska, a Siemens Mammomat 1000 X-ray machine was selected for analysis as the said mammography system is widely used in clinical practice. The variations in tube parameters (specific air kerma, high-voltage accuracy and reproducibility, linearity between exposure and dose exposure time) were monitored over a five-year period, from 2008 to 2012. In addition, due to observed daily fluctuations for chosen parameters, a series of measurements were performed three times a day within a single-month period (mainly October 2012). The goal of such an experimental set up is to assess short-term and long-term stability of tube parameters in the given mammography unit and to make a comparison between them. The present paper shows how an early detection of significant parameter fluctuations can help eliminate irregularities and optimize the performance of mammography systems.

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Research on the solidification of silt with cement and zeolite as additives

International Journal of Geology ◽

10.26789/ijg.2016.005 ◽

2016 ◽

Vol 1 (1) ◽

pp. 35

Author(s):

Feng Cheng ◽

Wang Baotian ◽

Li Shoude

Keyword(s):

Heavy Metal ◽

Industrial Pollution ◽

Unconfined Compressive Strength ◽

Effective Solution ◽

Short Term ◽

Time Saving ◽

Term Stability ◽

Long Term Stability ◽

Environment Problem

Silt solidification is an important method of silt disposal,and itâ€™s proved to be quick effectiveness and time saving and large in capacity.In recent years,the industrial pollution has made the silt in the lake or the sea rich in harmful elements,such as heavy metal and organic matter,etc,which may strongly influence the solidification effect of silt and trigger secondary pollution.The author proposed a kind of choice,which could effectly decrease harmful elements leaching,based on engineering application.The performances of solidification with different ratio of cement and zeolite,such as unconfined compressive strength,compression coefficient,heavy metal fractions,heavy metal short-term stability and long-term stability are systematicly studied.The article confirmed that the addition of the cement and the zeolite increase the strength of the soil and effectly enhance its deformation resistant capability,Further more,they significantly decrease the activity of harmful elements and greatly reduce the threat to the environment,which finds an effective solution to the environment problem.

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