Physics of Stratocumulus Top (POST): turbulence characteristics

Plante, I. Jen-La; Ma, Yuxin; Nurowska, Katarzyna; Gerber, H.; Khelif, D.; Karpińska, Katarzyna; Kopec, M. K.; Kumala, Wojciech; Malinowski, Szymon P.

doi:10.5194/acp-16-9711-2016

Cited by 33 publications

(70 citation statements)

References 40 publications

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“…4b) display a peak at f = 10 Hz. This phenomenon has been indicated in the previous analyses of POST (Jen-La Plante et al, 2016) and appears due to measurement errors. However, as the highest cutoff frequencies used in the present study are 5 Hz, it should not affect our results.…”

Section: Methods Based On Recovering the Missing Part Of The Spectrummentioning

confidence: 76%

“…Research aircraft are often not equipped to measure wind fluctuations with spatial resolution better than a few tens of meters (Wendisch and Brenguier, 2013). Due to various problems related to, for example, inhomogeneity of turbulence along the aircraft track and/or artifacts related to inevitable aerodynamic problems (Khelif et al, 1999;Kalgorios and Wang, 2002;Mallaun et al, 2015), estimates of at such low resolutions using power spectral density (PSD) or structure functions are complex and far from being standardized (e.g., compare procedures in Strauss et al, 2015;Jen-La Plante et al, 2016). The following question arises: can we do any better or can we at least introduce alternative methods to increase the robustness of retrievals?…”

Section: Introductionmentioning

confidence: 99%

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Novel approaches to estimating the turbulent kinetic energy dissipation rate from low- and moderate-resolution velocity fluctuation time series

Wacławczyk

Kopeć

et al. 2017

Atmos. Meas. Tech.

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Abstract. In this paper we propose two approaches to estimating the turbulent kinetic energy (TKE) dissipation rate, based on the zero-crossing method by Sreenivasan et al. (1983). The original formulation requires a fine resolution of the measured signal, down to the smallest dissipative scales. However, due to finite sampling frequency, as well as measurement errors, velocity time series obtained from airborne experiments are characterized by the presence of effective spectral cutoffs. In contrast to the original formulation the new approaches are suitable for use with signals originating from airborne experiments. The suitability of the new approaches is tested using measurement data obtained during the Physics of Stratocumulus Top (POST) airborne research campaign as well as synthetic turbulence data. They appear useful and complementary to existing methods. We show the number-of-crossings-based approaches respond differently to errors due to finite sampling and finite averaging than the classical power spectral method. Hence, their application for the case of short signals and small sampling frequencies is particularly interesting, as it can increase the robustness of turbulent kinetic energy dissipation rate retrieval.

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Section: Methods Based On Recovering the Missing Part Of The Spectrummentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Novel approaches to estimating the turbulent kinetic energy dissipation rate from low- and moderate-resolution velocity fluctuation time series

Wacławczyk

Kopeć

et al. 2017

Atmos. Meas. Tech.

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“…Katzwinkel et al () showed similar relationships between the inversion thickness, R i b , and wind shear using helicopter‐borne measurements with 0.06/s ≤ S ≤0.12/s and 0.2≤ R i b ≤0.7. These dependencies of R i b on S and Δ〈 θ v 〉/Δ z i can be used to approximately estimate the thickness of the entrainment interfacial layer when R i b reaches a critical value R i c (e.g., Jen‐La Plante et al, ; Katzwinkel et al, ):

normalΔ z_{i} = R i_{c} \frac{〈 {\overset{θ}{true}}_{v} 〉}{g} \frac{{false(normalΔ 〈 u 〉 false)}^{2} + {false(normalΔ 〈 v 〉 false)}^{2}}{normalΔ 〈 θ_{v} 〉} .

…”

Section: Resultsmentioning

confidence: 99%

Influences of Subsidence and Free‐Tropospheric Conditions on the Nocturnal Growth of Nonclassical Marine Stratocumulus

Pedersen

Grabowski

et al. 2018

J Adv Model Earth Syst

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Effects of free‐tropospheric thermodynamic properties and large‐scale subsidence on the nocturnal growth of marine stratocumulus clouds are investigated through large‐eddy simulation based on Flight 5 of the Physics of Stratocumulus Top research campaign. It was characterized by a weak inversion and moist troposphere. Sensitivity simulations are performed using variations in the subsidence and free‐tropospheric temperature and humidity. The results confirm that the cloud‐top entrainment instability parameter κ alone cannot unambiguously control the behaviors of marine stratocumulus due to the opposite response of liquid water path (LWP) to changes in the humidity and temperature jumps with the same variation in κ, thereby both jumps should be considered separately. However, sometimes it could be considered as a joint factor of the humidity and temperature jumps controlling LWP even though cloud‐top entrainment instability does not occur or κ < 0. An obvious role of subsidence is to push the inversion layer down nearly identically and at the same rate under different ambient conditions. Enhanced subsidence, as expected, diminishes the entrainment rate, cloud‐top height, cloud thickness, and LWP. However, it has a small influence on the inversion thickness and the dynamic instability across the inversion. An LWP budget analysis shows that the direct effect of subsidence is a small reduction in the LWP, but the indirect effect of subsidence is large due to contributions from other physical processes. Therefore, subsidence is an important physical process controlling the LWP budget, even though its direct contribution is significantly smaller than the largest contributions from both radiation and entrainment.

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“…2). While some studies extend the EIL into the cloud layer Jen-La Plante et al, 2016), this work defines the base of the EIL at cloud top (i.e., uppermost height where LWC ≥ 0.02 g m −3 ) for practical reasons since aerosol data from the PCASP and CPCs are not meaningful in the cloud layer. The top of the EIL is not as well defined as its base due to weaker vertical gradients of dynamic and thermodynamic properties relaxing to FT values over tens of meters at times (Wood, 2012).…”

Section: Layer Definitionsmentioning

confidence: 99%

“…This layer exhibits strong gradients in thermodynamic and dynamic properties. Although numerous airborne and modeling studies have attempted to increase our understanding about the thermodynamic and dynamic nature of the EIL (e.g., Caughey et al, 1982;Moeng et al, 2005;Haman et al, 2007;Wang et al, 2008;Carman et al, 2012;Katzwinkel et al, 2012;Gerber et al, 2013;Malinowski et al, 2013;Jen-La Plante et al, 2016), aerosol characteristics in this thin layer have not been studied in detail.…”

Section: Introductionmentioning

confidence: 99%

Aerosol characteristics in the entrainment interface layer in relation to the marine boundary layer and free troposphere

et al. 2018

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Abstract. This study uses airborne data from two field campaigns off the California coast to characterize aerosol size distribution characteristics in the entrainment interface layer (EIL), a thin and turbulent layer above marine stratocumulus cloud tops, which separates the stratocumulus-topped boundary layer (STBL) from the free troposphere (FT). The vertical bounds of the EIL are defined in this work based on considerations of buoyancy and turbulence using thermodynamic and dynamic data. Aerosol number concentrations are examined from three different probes with varying particle diameter (D p ) ranges: > 3 nm, > 10 nm, and 0.11-3.4 µm. Relative to the EIL and FT layers, the sub-cloud (SUB) layer exhibited lower aerosol number concentrations and higher surface area concentrations. High particle number concentrations between 3 and 10 nm in the EIL are indicative of enhanced nucleation, assisted by high actinic fluxes, cool and moist air, and much lower surface area concentrations than the STBL. Slopes of number concentration versus altitude in the EIL were correlated with the particle number concentration difference between the SUB and lower FT layers. The EIL aerosol size distribution was influenced by varying degrees from STBL aerosol versus subsiding FT aerosol depending on the case examined. These results emphasize the important role of the EIL in influencing nucleation and aerosol-cloudclimate interactions.

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Physics of Stratocumulus Top (POST): turbulence characteristics

Cited by 33 publications

References 40 publications

Novel approaches to estimating the turbulent kinetic energy dissipation rate from low- and moderate-resolution velocity fluctuation time series

Novel approaches to estimating the turbulent kinetic energy dissipation rate from low- and moderate-resolution velocity fluctuation time series

Influences of Subsidence and Free‐Tropospheric Conditions on the Nocturnal Growth of Nonclassical Marine Stratocumulus

Aerosol characteristics in the entrainment interface layer in relation to the marine boundary layer and free troposphere

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