Evaluation of forward-modelled attenuated backscatter using an urban ceilometer network in London under clear-sky conditions

Warren, Elliott; Charlton‐Perez, Cristina; Kotthaus, Simone; Lean, Humphrey; Ballard, Sue; Hopkin, Emma; Grimmond, Sue

doi:10.1016/j.atmosenv.2018.04.045

Cited by 18 publications

(31 citation statements)

References 81 publications

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“…Here, T w,eff is the effective transmission due to water vapor absorption. As the emitted spectrum of the ceilometers is much broader than the width of individual absorption lines, an effective transmission representative for λ on is calculated following Wiegner and Gasteiger (2015). In this context the center wavelength of the emitted spectrum and -to a lesser extent -the full width at half maximum (assuming a Gaussian profile) λ of the spectrum are crucial.…”

Section: Concept Based On Signalsmentioning

confidence: 99%

“…If the particle backscatter coefficient β p is used for validation, the signals must be inverted. As shown by Wiegner and Gasteiger (2015) the measured Vaisala signals are first corrected for water vapor absorption by being multiplied with T −2 w,eff (λ on ). Subsequently a standard inversion technique (Klett, 1981;Fernald, 1984) is applied.…”

Section: Concept Based On Particle Backscatter Coefficientsmentioning

confidence: 99%

“…11) is available from CeiLinEx2015: to calculate B(z) we use β m from the Rayleigh theory with the air density derived from radiosondes. The transmission T w,eff (λ on ) due to water vapor is calculated according to Wiegner and Gasteiger (2015) with the water vapor number density derived from the radiosondes as well, L p is estimated using the Angström exponent κ from AERONET or RALPH data, and β p and α p are derived from the inversion of coincident RALPH measurements.…”

Section: Case Date Timementioning

confidence: 99%

“…Wiegner et al (2014) discussed the problem in a general way on the basis of simulated signals and proposed an improved approach to correct for water vapor absorption. A follow-up paper (Wiegner and Gasteiger, 2015) developed a methodology that can routinely be applied to real measurements; it is used in the following. An alternative model was used by Madonna et al (2018) and applied to CL51 and CS135 measurements during INTERACT II.…”

Section: Introductionmentioning

confidence: 99%

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Aerosol backscatter profiles from ceilometers: validation of water vapor correction in the framework of CeiLinEx2015

Wiegner¹,

Mattis²,

Pattantyús-Ábrahám³

et al. 2019

Atmos. Meas. Tech.

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Abstract. With the rapidly growing number of automated single-wavelength backscatter lidars (ceilometers), their potential benefit for aerosol remote sensing received considerable scientific attention. When studying the accuracy of retrieved particle backscatter coefficients, it must be considered that most of the ceilometers are influenced by water vapor absorption in the spectral range around 910 nm. In the literature methodologies have been proposed to correct for this effect; however, a validation was not yet performed. In the framework of the ceilometer intercomparison campaign CeiLinEx2015 in Lindenberg, Germany, hosted by the German Weather Service, it was possible to tackle this open issue. Ceilometers from Lufft (CHM15k and CHM15kx, operating at 1064 nm), from Vaisala (CL51 and CL31) and from Campbell Scientific (CS135), all operating at a wavelength of approximately 910 nm, were deployed together with a multi-wavelength research lidar (RALPH) that served as a reference. In this paper the validation of the water vapor correction is performed by comparing ceilometer backscatter signals with measurements of the reference system extrapolated to the water vapor regime. One inherent problem of the validation is the spectral extrapolation of particle optical properties. For this purpose AERONET measurements and inversions of RALPH signals were used. Another issue is that the vertical range where validation is possible is limited to the upper part of the mixing layer due to incomplete overlap and the generally low signal-to-noise ratio and signal artifacts above that layer. Our intercomparisons show that the water vapor correction leads to quite a good agreement between the extrapolated reference signal and the measurements in the case of CL51 ceilometers at one or more wavelengths in the specified range of the laser diode's emission. This ambiguity is due to the similar effective water vapor transmission at several wavelengths. In the case of CL31 and CS135 ceilometers the validation was not always successful. That suggests that error sources beyond the water vapor absorption might be dominant. For future applications we recommend monitoring the emitted wavelength and providing “dark” measurements on a regular basis.

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Section: Concept Based On Signalsmentioning

confidence: 99%

Section: Concept Based On Particle Backscatter Coefficientsmentioning

confidence: 99%

Section: Case Date Timementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Aerosol backscatter profiles from ceilometers: validation of water vapor correction in the framework of CeiLinEx2015

Wiegner¹,

Mattis²,

Pattantyús-Ábrahám³

et al. 2019

Atmos. Meas. Tech.

View full text Add to dashboard Cite

show abstract

“…Recently ceilometer data were used for the validation of transport models, e.g. to improve forecasts of the dispersion of aerosol layers (e.g., Emeis et al, 2011;Cazorla et al, 2017;Chan et al, 2018), and to support air quality studies (e.g., Schäfer et al, 2011;Geiß et al, 2017;Kotthaus and Grimmond, 2018b), whereas data assimilation in numerical weather forecast models is still limited to case studies (e.g., Geisinger, 2017;Warren et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Aerosol backscatter profiles from ceilometers: validation of water vapor correction in the framework of CeiLinEx2015

Wiegner¹,

Mattis²,

Pattantyús-Ábrahám³

et al. 2018

Preprint

View full text Add to dashboard Cite

Abstract. With the rapidly growing number of automated single-wavelength backscatter lidars (ceilometers) their potential benefit for aerosol remote sensing received considerable scientific attention. When studying the accuracy of retrieved particle backscatter coefficients it must be considered that most of the ceilometers are influenced by water vapor absorption in the spectral range around 910 nm. In the literature methodologies to correct for this effect have been proposed, however, a validation was not yet performed. In the framework of the ceilometer intercomparison campaign CeiLinEx2015 in Lindenberg, Germany, hosted by the German Weather Service, it was possible to tackle this open issue. Ceilometers from Lufft (CHM15k and CHM15kx, operating at 1064 nm), from Vaisala (CL51 and CL31) and from Campbell Scientific (CS135), all operating at a wavelength of approximately 910 nm, were deployed together with a multi-wavelength research lidar (RALPH) that served as reference. In this paper the validation of the water vapor correction is performed by comparing ceilometer backscatter signals with measurements of the reference system extrapolated to the water vapor regime. One inherent problem of the validation is the spectral extrapolation of particle optical properties. For this purpose AERONET measurements and inversions of RALPH signals were used. Another issue is that the vertical range where validation is possible is limited to the upper part of the mixing layer due incomplete overlap, and the in general low signal to noise ratio and signal artefacts above that layer. Our intercomparisons show that the water vapor correction leads to a quite good agreement between the extrapolated reference signals and the measurements in the case of CL51 ceilometers at one or more wavelengths in the specified range of the laser diode's emission. This equivocation is due to the similar effective water vapor transmission at several wavelengths. In the case of CL31 and CS135 ceilometers the validation was not always successful. That suggests that error sources beyond the water vapor absorption might be dominant. For future applications we recommend to monitor the emitted wavelength and to provide dark measurements on a regular basis.

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Exploring the characteristics of a vehicle‐based temperature dataset for kilometre‐scale data assimilation

Bell

Dance

Waller

2022

Meteorological Applications

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Crowdsourced vehicle-based observations have the potential to improve forecast skill in convection-permitting numerical weather prediction (NWP). The aim of this paper is to explore the characteristics of vehicle-based observations of air temperature in the context of data assimilation. We describe a novel lowprecision vehicle-based observation dataset obtained from a Met Office proofof-concept trial. In this trial, observations of air temperature were obtained from built-in vehicle air-temperature sensors, broadcast to an application on the participant's smartphone, and uploaded, with relevant metadata, to the Met Office servers. We discuss the instrument and representation uncertainties

show abstract

Evaluation of forward-modelled attenuated backscatter using an urban ceilometer network in London under clear-sky conditions

Cited by 18 publications

References 81 publications

Aerosol backscatter profiles from ceilometers: validation of water vapor correction in the framework of CeiLinEx2015

Aerosol backscatter profiles from ceilometers: validation of water vapor correction in the framework of CeiLinEx2015

Aerosol backscatter profiles from ceilometers: validation of water vapor correction in the framework of CeiLinEx2015

Exploring the characteristics of a vehicle‐based temperature dataset for kilometre‐scale data assimilation

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