Microphysical properties of stratocumulus clouds

Pawłowska, Hanna; Brenguier, Jean‐Louis; Burnet, Frédéric

doi:10.1016/s0169-8095(00)00054-5

Cited by 84 publications

(75 citation statements)

References 30 publications

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“…This prediction of the macroscale theory is well supported by observations. For example, in stratocumulus clouds, the liquid water mixing ratio is close to adiabatic, except when approaching the cloud top (see Figure 3 in Pawlowska et al, 2000).…”

Section: Activation and Growth Of Cloud Dropletsmentioning

confidence: 99%

Droplet growth in warm turbulent clouds

Devenish

Bartello

Brenguier

et al. 2012

Quart J Royal Meteoro Soc

239

281

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In this survey we consider the impact of turbulence on cloud formation from the cloud scale to the droplet scale. We assess progress in understanding the effect of turbulence on the condensational and collisional growth of droplets and the effect of entrainment and mixing on the droplet spectrum. The increasing power of computers and better experimental and observational techniques allow for a much more detailed study of these processes than was hitherto possible. However, much of the research necessarily remains idealized and we argue that it is those studies which include such fundamental characteristics of clouds as droplet sedimentation and latent heating that are most relevant to clouds. Nevertheless, the large body of research over the last decade is beginning to allow tentative conclusions to be made. For example, it is unlikely that small-scale turbulent eddies (i.e. not the energy-containing eddies) alone are responsible for broadening the droplet size spectrum during the initial stage of droplet growth due to condensation. It is likely, though, that small-scale turbulence plays a significant role in the growth of droplets through collisions and coalescence. Moreover, it has been possible through detailed numerical simulations to assess the relative importance of different processes to the turbulent collision kernel and how this varies in the parameter space that is important to clouds. The focus of research on the role of turbulence in condensational and collisional growth has tended to ignore the effect of entrainment and mixing and it is arguable that they play at least as important a role in the evolution of the droplet spectrum. We consider the role of turbulence in the mixing of dry and cloudy air, methods of quantifying this mixing and the effect that it has on the droplet spectrum. Copyright

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Section: Activation and Growth Of Cloud Dropletsmentioning

confidence: 99%

Droplet growth in warm turbulent clouds

Devenish

Bartello

Brenguier

et al. 2012

Quart J Royal Meteoro Soc

239

281

View full text Add to dashboard Cite

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“…Typically, the maximum of the LWC envelope increases linearly with height, suggesting the presence of parcels lifted (almost) adiabatically from the cloud base (cf. Pawlowska et al, 2000) or even from the surface. Parcels with reduced LWC most often appear in the CTMSL, while in the CTL a depletion of LWC is less common and indicates the presence of cloud holes (Gerber et al, 2005), i.e., parcels of negative buoyancy, formed in the course of mixing and evaporative cooling at the cloud top, slowly descending across the cloud deck as shown in Fig.…”

Section: Lwc Profilesmentioning

confidence: 99%

Physics of Stratocumulus Top (POST): turbulent mixing across capping inversion

et al. 2013

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Abstract. High spatial resolution measurements of temperature and liquid water content, accompanied by moderateresolution measurements of humidity and turbulence, collected during the Physics of Stratocumulus Top experiment are analyzed. Two thermodynamically, meteorologically and even optically different cases are investigated. An algorithmic division of the cloud-top region into layers is proposed. Analysis of dynamic stability across these layers leads to the conclusion that the inversion capping the cloud and the cloud-top region is turbulent due to the wind shear, which is strong enough to overcome the high static stability of the inversion. The thickness of this mixing layer adapts to wind and temperature jumps such that the gradient Richardson number stays close to its critical value. Turbulent mixing governs transport across the inversion, but the consequences of this mixing depend on the thermodynamic properties of cloud top and free troposphere. The effects of buoyancy sorting of the mixed parcels in the cloud-top region are different in conditions that permit or prevent cloud-top entrainment instability. Removal of negatively buoyant air from the cloud top is observed in the first case, while buildup of the diluted cloud-top layer is observed in the second one.

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“…2a. Some studies showed that liquid water content (LWC) is adiabatic or near-adiabatic within St/Sc (e.g., Albrecht et al, 1990;Zuidema et al, 2005), while others found that LWC can deviate substantially from adiabaticity (e.g., Pawlowska et al, 2000;Zhou et al, 2006). In either case, LWP is directly related to h, as LWP is the integral of LWC over the cloud depth (Zhou et al, 2006): where A is the adiabatic rate of change with height of LWC and α is the percentage of adiabaticity.…”

Section: Satellite Comparison Of Cloud Properties With Ship Observationsmentioning

confidence: 99%

A comparison of ship and satellite measurements of cloud properties with global climate model simulations in the southeast Pacific stratus deck

et al. 2010

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Abstract. Here, liquid water path (LWP), cloud fraction, cloud top height, and cloud base height retrieved by a suite of A-train satellite instruments (the CPR aboard CloudSat, CALIOP aboard CALIPSO, and MODIS aboard Aqua) are compared to ship observations from research cruises made in 2001 and 2003-2007 into the stratus/stratocumulus deck over the southeast Pacific Ocean. It is found that CloudSat radar-only LWP is generally too high over this region and the CloudSat/CALIPSO cloud bases are too low. This results in a relationship (LWP∼h 9 ) between CloudSat LWP and CALIPSO cloud thickness (h) that is very different from the adiabatic relationship (LWP∼h 2 ) from in situ observations. Such biases can be reduced if LWPs suspected to be contaminated by precipitation are eliminated, as determined by the maximum radar reflectivity Z max >−15 dBZ in the apparent lower half of the cloud, and if cloud bases are determined based upon the adiabatically-determined cloud thickness (h∼LWP 1/2 ). Furthermore, comparing results from a global model (CAM3.1) to ship observations reveals that, while the simulated LWP is quite reasonable, the model cloud is too thick and too low, allowing the model to have LWPs that are almost independent of h. This model can also obtain a reasonable diurnal cycle in LWP and cloud fraction at a location roughly in the centre of this region (20 • S, 85 • W) but has an opposite diurnal cycle to those observed aboard ship at a location closer to the coast (20 • S, 75 • W). The diurnal cycle at the latter location is slightly improved in the newest version of the model (CAM4). However, the simulated clouds remain too thick and too low, as cloud bases are usually at or near the surface.

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Microphysical properties of stratocumulus clouds

Cited by 84 publications

References 30 publications

Droplet growth in warm turbulent clouds

Droplet growth in warm turbulent clouds

Physics of Stratocumulus Top (POST): turbulent mixing across capping inversion

A comparison of ship and satellite measurements of cloud properties with global climate model simulations in the southeast Pacific stratus deck

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