Quantification of waves in lidar observations of noctilucent clouds at scales from seconds to minutes

Kaifler, Natalie; Baumgarten, Gerd; Fiedler, Jens; Lübken, Franz‐Josef

doi:10.5194/acp-13-11757-2013

Cited by 20 publications

(18 citation statements)

References 55 publications

(59 reference statements)

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“…For 69 ∘ N, Kaifler et al (2011) listed significantly wider layers (1.68-km vertical extent vs. 900 m reported here). In terms of vertical displacement, downward progression, and mean duration, this NLC event yields similar values as observed at 69 ∘ N and 69 ∘ S (Kaifler et al, 2013).…”

Section: Comparison To Midlatitude Nlc Statistics and Relation To Temsupporting

confidence: 70%

“…For the first time, the CARMA model (Jensen & Thomas, 1989;Rapp & Thomas, 2006;Toon et al, 1979;Turco et al, 1979Turco et al, , 1982 is driven with lidar temperature measurements for one-dimensional simulations. Within CARMA, ice particles form via heterogeneous nucleation and grow or sublimate according to the ambient conditions described by temperature and saturation.…”

Section: Microphysical Evolution Of Nlc Particlesmentioning

confidence: 99%

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Mesospheric Temperature During the Extreme Midlatitude Noctilucent Cloud Event on 18/19 July 2016

Kaifler

Wilms

et al. 2018

JGR Atmospheres

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A rare noctilucent cloud (NLC) event was observed at 48.8∘ N, 13.7∘ E above GERman Experimental Seismic System station in southern Germany on 18/19 July 2016 using the Compact Rayleigh Autonomous Lidar. Strong southward winds due to a quasi 2‐day planetary wave allowed for the influx of mesospheric polar air to midlatitudes on this day. The NLC observed by lidar was preceded by strong NLC displays in Cloud Imaging and Particle Size (CIPS) Experiment satellite images above the North Sea and by strong mesospheric summer radar echoes 800 km north of the lidar site and was also observed visually in central Europe. The NLC occurred at low altitude and was bright and thin with strong oscillations in altitude and brightness. Darkness allowed for high‐resolution temperature measurements at NLC altitudes. The ice particles were embedded in the upper part of a cold region with temperatures below 150 K. Significantly higher temperatures were found directly above the cloud with large vertical temperature gradients of 25 K/km at the top boundary. Spectral analysis reveals that NLC particles existed within cold phases of gravity waves within a region of high static stability. In order to study the evolution of NLC brightness in this environment, we drive the microphysical model Community Aerosol and Radiation Model for Atmospheres with lidar temperature soundings. We find that NLC particles can survive and grow in the conditions defining this midlatitude event. We conclude that the ice particles did not nucleate at the site of observation but were meridionally transported and vertically confined to a thin layer due to a large vertical temperature gradient, wind reversal, and low levels of mesospheric turbulence.

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Section: Comparison To Midlatitude Nlc Statistics and Relation To Temsupporting

confidence: 70%

Section: Microphysical Evolution Of Nlc Particlesmentioning

confidence: 99%

Mesospheric Temperature During the Extreme Midlatitude Noctilucent Cloud Event on 18/19 July 2016

Kaifler

Wilms

et al. 2018

JGR Atmospheres

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“…In recent years NLCs have been intensely studied using ground-based (e.g. Demissie et al, 2014;Kaifler et al, 2013;Kirkwood et al, 2008) and space-borne (e.g. DeLand et al, 2007;Hervig et al, 2016;Rong et al, 2015) methods.…”

Section: Introductionmentioning

confidence: 99%

Unravelling the microphysics of polar mesospheric cloud formation

2019

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Polar mesospheric clouds are the highest water ice clouds occurring in the terrestrial atmosphere. They form in the polar summer mesopause, the coldest region in the atmosphere. It has long been assumed that these clouds form by heterogeneous nucleation on meteoric smoke particles which are the remnants of material ablated from meteoroids in the upper atmosphere. However, until now little was known about the properties of these nanometre-sized particles and application of the classical theory for heterogeneous ice nucleation was impacted by large uncertainties. In this work, we performed laboratory measurements on the heterogeneous ice formation process at mesopause conditions on small (r = 1 to 3 nm) iron silicate nanoparticles serving as meteoric smoke analogues. We observe that ice growth on these particles sets in for saturation ratios with respect to hexagonal ice below S h = 50, a value that is commonly exceeded during the polar mesospheric cloud season, affirming meteoric smoke particles as likely nuclei for heterogeneous ice formation in mesospheric clouds. We present a simple ice-activation model based on the Kelvin-Thomson equation that takes into account the water coverage of iron silicates of various compositions. The activation model reproduces the experimental data very well using bulk properties of compact amorphous solid water. This is in line with the finding from our previous study that ice formation on iron silicate nanoparticles occurs by condensation of amorphous solid water rather than by nucleation of crystalline ice at mesopause conditions. Using the activation model, we also show that for iron silicate particles with dry radius larger than r = 0.6 nm the nanoparticle charge has no significant effect on the ice-activation threshold.

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“…In particular, dynamical properties are commonly inferred from NLC measurements. For example, wave parameters and wind velocities have been determined from ground-based NLC photography [e.g., Witt, 1962;Pautet et al, 2011], from NLC lidar measurements [e.g., Kaifler et al, 2013a], and from satellite measurements of NLCs [e.g., Chandran et al, 2009;Rong et al, 2015]. Kelvin-Helmholtz instabilities have been identified to cause small-scale structures of NLCs [Baumgarten and Fritts, 2014].…”

Section: Introductionmentioning

confidence: 99%

Nucleation of mesospheric cloud particles: Sensitivities and limits

2016

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Nucleation of mesospheric ice particles is thought to occur via heterogeneous nucleation on meteor smoke particles. However, several factors determining the nucleation rate are poorly known. To study the effect of uncertainties in the nucleation rate on cloud properties, we use the Community Aerosol and Radiation Model for Atmospheres and systematically vary the nucleation rate over ±10 orders of magnitude. In one set of simulations, the background state of the atmosphere is described by climatological conditions. In a second set, gravity wave‐perturbed profiles from the Kühlungsborn Mechanistic general Circulation Model (KMCM) are used with typical temperature (vertical wind) perturbations at the mesopause on the order of 9 K (0.45 m/s). The resulting noctilucent cloud (NLC) characteristics are compared to lidar and satellite measurements. Realistic NLCs compared to the lidar measurements can only be modeled if the nucleation rate is reduced by up to 3 orders of magnitude compared to standard assumptions. For the same cases, the simulated NLCs compare best to the satellite measurements if the nucleation rate is reduced by 2 orders of magnitude or more. Dynamical processes at the mesopause strongly influence the NLC development. In a gravity wave‐perturbed atmosphere, the ice particles have only limited time for nucleation and growth. The growth time is limited by the vertical wind, because the vertical wind determines the residence time of the ice particles in the supersaturated region. Since the vertical wind amplitudes reach 1.5 m/s in KMCM (compared to a mean upwelling of ∼4 cm/s in the climatology), the ice particles remain significantly smaller in a gravity wave‐perturbed atmosphere than in climatological background conditions.

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Quantification of waves in lidar observations of noctilucent clouds at scales from seconds to minutes

Cited by 20 publications

References 55 publications

Mesospheric Temperature During the Extreme Midlatitude Noctilucent Cloud Event on 18/19 July 2016

Mesospheric Temperature During the Extreme Midlatitude Noctilucent Cloud Event on 18/19 July 2016

Unravelling the microphysics of polar mesospheric cloud formation

Nucleation of mesospheric cloud particles: Sensitivities and limits

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