The onset of precipitation in warm cumulus clouds: An observational case‐study

Burnet, Frédéric; Brenguier, Jean‐Louis

doi:10.1002/qj.552

Cited by 16 publications

(13 citation statements)

References 21 publications

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“…Different growth histories were experienced by the droplets due to entrainment and mixing, as originally envisioned by Baker and Latham (1979). Burnet and Brenguier (2010) also showed how difficult it is to make observations of the development of precipitation with aircraft and radar. This difficulty was addressed to some extent in the RICO field experiment (Rauber et al, 2007), because of the statistical sampling strategy.…”

Section: Introductionmentioning

confidence: 71%

“…The main effect of the increase in concentration of CCN is that the rain lasts for a significantly shorter period of time: the 30 dBZ echo intersects the ground for about 10 min less than in the standard run. The dynamics of the cloud are important, as highlighted by Burnet and Brenguier (2010). If the production of precipitation were delayed beyond the development stage of the cloud when the updraught has ceased and the liquid water content has decayed, the embryonic raindrops would not be able to grow.…”

Section: Sensitivity Studiesmentioning

confidence: 99%

“…Burnet and Brenguier (2010) examined data collected in the 10 August cloud during SCMS and highlighted how sensitive the onset of precipitation is to cloud dynamics. Two clouds collapsed after reaching an altitude of 3 km above sea level, without producing any precipitation, while the third one reached a higher level of 4 km and produced significant precipitation.…”

Section: Introductionmentioning

confidence: 99%

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The production of warm rain in shallow maritime cumulus clouds

Blyth

Lowenstein

Huang

et al. 2012

Quart J Royal Meteoro Soc

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The problem of the production of warm rain by collision and coalescence has been studied for over half a century and several processes have been suggested to explain the observed production, which is more rapid than generally possible with models. A straightforward scenario in relatively shallow maritime cumulus clouds is one where cloud drops simply grow by condensation and coalescence, with no appeal to enhancement due to entrainment or turbulence or indeed the presence of giant and ultragiant aerosols that may exist in the boundary layer. However, it is difficult in a field experiment to measure the concentrations of aerosols and the time evolution of the droplet size distribution or reflectivity in individual clouds. The Rain in Cumulus Over the Ocean (RICO) field experiment overcame some of these difficulties due to the abundance of clouds and the statistical sampling strategy at all significant altitudes. In this article, we present the results of the rate of increase in the radar reflectivity in a couple of cases. Comparisons with a cloud model strongly suggest that the development of warm rain can be explained using the observed aerosol distribution alone. Sensitivity studies suggested that giant and ultragiant aerosols were unimportant for the production of rain in these clouds.

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Section: Introductionmentioning

confidence: 71%

Section: Sensitivity Studiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The production of warm rain in shallow maritime cumulus clouds

Blyth

Lowenstein

Huang

et al. 2012

Quart J Royal Meteoro Soc

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“…This is illustrated in Fig. 3 with data collected in a cumulus cloud during the SCMS flight me11 (Cell A in Burnet and Brenguier, 2010). During this campaign, cloud sampling started in active convective turrets and lasted until they were collapsing.…”

Section: Intra-cloud Variability Of the Microphysicsmentioning

confidence: 96%

Cloud optical thickness and liquid water path – does the <i>k</i> coefficient vary with droplet concentration?

2011

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Abstract. Cloud radiative transfer calculations in general circulation models involve a link between cloud microphysical and optical properties. Indeed, the liquid water content expresses as a function of the mean volume droplet radius, while the light extinction is a function of their mean surface radius. There is a small difference between these two parameters because of the droplet spectrum width. This issue has been addressed by introducing an empirical multiplying correction factor to the droplet concentration. Analysis of in situ sampled data, however, revealed that the correction factor decreases when the concentration increases, hence partially mitigating the aerosol indirect effect.Five field experiments are reanalyzed here, in which standard and upgraded versions of the droplet spectrometer were used to document shallow cumulus and stratocumulus topped boundary layers. They suggest that the standard probe noticeably underestimates the correction factor compared to the upgraded versions. The analysis is further refined to demonstrate that the value of the correction factor derived by averaging values calculated locally along the flight path overestimates the value derived from liquid water path and optical thickness of a cloudy column, and that there is no detectable relationship between the correction factor and the droplet concentration. It is also shown that the droplet concentration dilution by entrainment-mixing after CCN activation is significantly stronger in shallow cumuli than in stratocumulus layers. These various effects are finally combined to produce the today best estimate of the correction factor to use in general circulation models.

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“…This large difference can be explained by the existence of the transition layer (as discussed in Sect. 3) near the lifting condensation level (LCL) in warm convective cloud fields, which is the approximated height of a convective cloud base (Craven et al, 2002;Meerkötter and Bugliaro, 2009). Within this layer parcels rising from the sub-cloudy layer are generally colder than parcels subsiding from the cloudy layer.…”

Section: Partition To Different Core Typesmentioning

confidence: 99%

Core and margin in warm convective clouds – Part 1: Core types and evolution during a cloud's lifetime

et al. 2019

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Abstract. The properties of a warm convective cloud are determined by the competition between the growth and dissipation processes occurring within it. One way to observe and follow this competition is by partitioning the cloud to core and margin regions. Here we look at three core definitions, namely positive vertical velocity (Wcore), supersaturation (RHcore), and positive buoyancy (Bcore), and follow their evolution throughout the lifetime of warm convective clouds. Using single cloud and cloud field simulations with bin-microphysics schemes, we show that the different core types tend to be subsets of one another in the following order: Bcore⊆RHcore⊆Wcore. This property is seen for several different thermodynamic profile initializations and is generally maintained during the growing and mature stages of a cloud's lifetime. This finding is in line with previous works and theoretical predictions showing that cumulus clouds may be dominated by negative buoyancy at certain stages of their lifetime. The RHcore–Wcore pair is most interchangeable, especially during the growing stages of the cloud. For all three definitions, the core–shell model of a core (positive values) at the center of the cloud surrounded by a shell (negative values) at the cloud periphery applies to over 80 % of a typical cloud's lifetime. The core–shell model is less appropriate in larger clouds with multiple cores displaced from the cloud center. Larger clouds may also exhibit buoyancy cores centered near the cloud edge. During dissipation the cores show less overlap, reduce in size, and may migrate from the cloud center.

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The onset of precipitation in warm cumulus clouds: An observational case‐study

Cited by 16 publications

References 21 publications

The production of warm rain in shallow maritime cumulus clouds

The production of warm rain in shallow maritime cumulus clouds

Cloud optical thickness and liquid water path – does the <i>k</i> coefficient vary with droplet concentration?

Core and margin in warm convective clouds – Part 1: Core types and evolution during a cloud's lifetime

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The onset of precipitation in warm cumulus clouds: An observational case‐study

Cited by 16 publications

References 21 publications

The production of warm rain in shallow maritime cumulus clouds

The production of warm rain in shallow maritime cumulus clouds

Cloud optical thickness and liquid water path – does the &lt;i&gt;k&lt;/i&gt; coefficient vary with droplet concentration?

Core and margin in warm convective clouds – Part 1: Core types and evolution during a cloud's lifetime

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Product

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Cloud optical thickness and liquid water path – does the <i>k</i> coefficient vary with droplet concentration?