A Quantitative Comparison of Ground-Based FSSP and PVM Measurements

Wendisch, Manfred

doi:10.1175/1520-0426(1998)015<0887:aqcogb>2.0.co;2

Cited by 24 publications

(9 citation statements)

References 30 publications

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“…The parameter m was considered to be constant and set to 0.73 as proposed by the manufacturer. In addition, the concentration was corrected for a varying velocity acceptance ratio (Wendisch, 1998), which was simultaneously measured. A comparison of different correction schemes for concentration measurements with the FSSP is given by Brenguier (1989).…”

Section: Methodsmentioning

confidence: 99%

“…The LWC , calculated from the corrected FSSP data [], were compared to the LWC directly measured by the PVM, which revealed the following correlation equation (correlation coefficient R 2 of 0.81): The systematic underestimation of the LWC by the PVM may be a result of decreasing sensitivity of the PVM with increasing droplet diameter as reported by Arends et al (1992), Wendisch et al (1998) and Wendisch (1998), but may also be explained by a varying sample volume of the FSSP. Wind tunnel tests of the airborne version of the PVM (the PVM‐100A) have also shown a decreasing sensitivity of the PVM with increasing droplet diameter (Wendisch et al, 2001).…”

Section: Methodsmentioning

confidence: 99%

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Size-dependent aerosol activation at the high-alpine site Jungfraujoch (3580 m asl)

Henning

Weingärtner

Schmidt³

et al. 2002

Tellus B

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Microphysical and chemical aerosol properties and their influence on cloud formation were studied in a field campaign at the high‐alpine site Jungfraujoch (JFJ, 3580 m asl). Due to its altitude, this site is suitable for ground‐based in‐cloud measurements, with a high cloud frequency of 40%. Dry total and interstitial aerosol size distributions [18 nm 100 nm) number concentration (Ntot,Dp>100) was only found for concentrations less than 100 cm−3. For higher values of Ntot,Dp>100 the D50 remained constant. Furthermore, a decrease of the effective radius of cloud droplets (Reff) with increasing Ntot,Dp>100 was observed, providing experimental evidence for the microphysical relation predicted by the Twomey effect. A modified Köhler model was used to quantify the critical supersaturation for the aerosol observed at the JFJ. Ambient supersaturations were determined from the derived supersaturation curve and the calculated D50. As an example, a critical supersaturation of 0.2% was found for 100 nm particles.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Size-dependent aerosol activation at the high-alpine site Jungfraujoch (3580 m asl)

Henning

Weingärtner

Schmidt³

et al. 2002

Tellus B

View full text Add to dashboard Cite

show abstract

“…Consistently, Meyer et al (1980) observed that droplets were formed at 1-2 km visibility range, and Jiusto (1981) defined light fog by visibility between 1 and 5 km. Such visibility was caused by few rather large droplets that contributed more to LWC and less to the extinction coefficient: the droplet effective diameter was larger than the monthly average of 15 ± 3 µm, similar to Wendisch et al (1998), and droplet number concentration was smaller (8-45 cm −3 ) than the monthly average of 100 ± 50 cm −3 . That high values of fog visibility demonstrate that the diffusometer alone is not able to distinguish the main cause of the visibility reduction, between aerosols or droplets.…”

Section: Fogmentioning

confidence: 99%

Enhanced extinction of visible radiation due to hydrated aerosols in mist and fog

Elías¹,

Dupont

Hammer

et al. 2015

Atmos. Chem. Phys.

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Abstract. The study assesses the contribution of aerosols to the extinction of visible radiation in the mist-fog-mist cycle. Relative humidity is large in the mist-fog-mist cycle, and aerosols most efficient in interacting with visible radiation are hydrated and compose the accumulation mode. Measurements of the microphysical and optical properties of these hydrated aerosols with diameters larger than 0.4 µm were carried out near Paris, during November 2011, under ambient conditions. Eleven mist-fog-mist cycles were observed, with a cumulated fog duration of 96 h, and a cumulated mist-fogmist cycle duration of 240 h.In mist, aerosols grew by taking up water at relative humidities larger than 93 %, causing a visibility decrease below 5 km. While visibility decreased down from 5 to a few kilometres, the mean size of the hydrated aerosols increased, and their number concentration (N ha ) increased from approximately 160 to approximately 600 cm −3 . When fog formed, droplets became the strongest contributors to visible radiation extinction, and liquid water content (LWC) increased beyond 7 mg m −3 . Hydrated aerosols of the accumulation mode co-existed with droplets, as interstitial non-activated aerosols. Their size continued to increase, and some aerosols achieved diameters larger than 2.5 µm. The mean transition diameter between the aerosol accumulation mode and the small droplet mode was 4.0 ± 1.1 µm. N ha also increased on average by 60 % after fog formation. Consequently, the mean contribution to extinction in fog was 20 ± 15 % from hydrated aerosols smaller than 2.5 µm and 6 ± 7 % from larger aerosols. The standard deviation was large because of the large variability of N ha in fog, which could be smaller than in mist or 3 times larger.The particle extinction coefficient in fog can be computed as the sum of a droplet component and an aerosol component, which can be approximated by 3.5 N ha (N ha in cm −3 and particle extinction coefficient in Mm −1 ). We observed an influence of the main formation process on N ha , but not on the contribution to fog extinction by aerosols. Indeed, in fogs formed by stratus lowering (STL), the mean N ha was 360 ± 140 cm −3 , close to the value observed in mist, while in fogs formed by nocturnal radiative cooling (RAD) under cloud-free sky, the mean N ha was 600 ± 350 cm −3 . But because visibility (extinction) in fog was also lower (larger) in RAD than in STL fogs, the contribution by aerosols to extinction depended little on the fog formation process. Similarly, the proportion of hydrated aerosols over all aerosols (dry and hydrated) did not depend on the fog formation process.Measurements showed that visibility in RAD fogs was smaller than in STL fogs due to three factors: (1) LWC was larger in RAD than in STL fogs, (2) droplets were smaller, (3) hydrated aerosols composing the accumulation mode were more numerous.

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“…It should be noted that the FSSP has both sizing and counting deficiencies [Dye and Baurngardner, 1984; Baurngardner et al, 1985; Baumgardner and Spowart, 1990] which in turn can cause errors in the measurements of re [Gerber, 1996;Wendisch, 1998]. However, the focus of this study is on ix, its dependence on the spectral dispersion, and its effect on the parameterized re given L and N. Any error in L and/or N will exert the same effect on all the parameterization schemes.…”

Section: Comparison Of Measured and Parameterized R•mentioning

confidence: 99%

Spectral dispersion of cloud droplet size distributions and the parameterization of cloud droplet effective radius

Liu

Daum

2000

Geophysical Research Letters

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A Quantitative Comparison of Ground-Based FSSP and PVM Measurements

Cited by 24 publications

References 30 publications

Size-dependent aerosol activation at the high-alpine site Jungfraujoch (3580 m asl)

Size-dependent aerosol activation at the high-alpine site Jungfraujoch (3580 m asl)

Enhanced extinction of visible radiation due to hydrated aerosols in mist and fog

Spectral dispersion of cloud droplet size distributions and the parameterization of cloud droplet effective radius

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