Relationships between CCN and cloud microphysics variations in clean maritime air

Hudson, James G.; Mishra, Subhashree

doi:10.1029/2007gl030044

Cited by 57 publications

(72 citation statements)

References 12 publications

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“…The CCN distribution was measured with the CCN spectrometer (Hudson and Mishra, 2007). The DSDs were measured by the FSSP, two-dimensional optical array cloud probe (2D-C, 42 µm ≤ d ≤ 1.6 mm with image reconstruction) and PMS two-dimensional optical array precipitation probe (2D-P, 145 µm ≤ d ≤ 12.7 mm with image reconstruction).…”

Section: The Rico Field Experimentsmentioning

confidence: 99%

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: The Rico Field Experimentsmentioning

confidence: 99%

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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“…Rudich et al (2002) found that in the continental region around the Aral Sea large saltcontaining dust particles increase cloud drops to sizes that promote precipitation. Through modeling and based on aircraft measurements done in the Caribbean, Teller and Levin (2006) and Hudson and Mishra (2007), respectively, found that GN have little influence on precipitation when CCN con-centrations are low. Blyth et al (2013) also claim that GN are unimportant for the warm rain process in shallow, maritime clouds and suggest in addition that this process can be modeled relatively simply based on condensational growth of droplets formed on sub-cloud aerosol particles.…”

mentioning

confidence: 99%

“…Above 0 • C only warm clouds exist, in which, after the activation of aerosol particles, a number of processes influence the further development of the cloud and its droplets, among them coagulation, condensation, and entrainment and mixing at the cloud edges. The influence of atmospheric aerosol particles and particularly of CCN on clouds is discussed in the context of the droplet number concentration, droplet size, the amount of drizzle forming from a cumulus cloud, and cloud coverage (e.g., Heymsfield and McFarquhar, 2001;Conant et al, 2004;Hudson and Mishra, 2007;Kaufman et al, 2005). Particularly the role of aerosol particles in the formation of precipitation remains controversial (Stevens and Feingold, 2009), as meteorological conditions might be of great importance for these processes, too.…”

mentioning

confidence: 99%

Aerosol arriving on the Caribbean island of Barbados: physical properties and origin

et al. 2016

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Abstract. The marine aerosol arriving at Barbados (Ragged Point) was characterized during two 3-week long measurement periods in November 2010 and April 2011, in the context of the measurement campaign CARRIBA (Cloud, Aerosol, Radiation and tuRbulence in the trade wInd regime over BArbados). Through a comparison between groundbased and airborne measurements it was shown that the former are representative of the marine boundary layer at least up to cloud base. In general, total particle number concentrations (N total ) ranged from as low as 100 up to 800 cm −3 , while number concentrations for cloud condensation nuclei (N CCN ) at a supersaturation of 0.26 % ranged from some 10 to 600 cm −3 . N total and N CCN depended on the air mass origin. Three distinct types of air masses were found. One type showed elevated values for both N total and N CCN and could be attributed to long-range transport from Africa, by which biomass burning particles from the Sahel region and/or mineral dust particles from the Sahara were advected. The second and third type both had values for N CCN below 200 cm −3 and a clear minimum in the particle number size distribution (NSD) around 70 to 80 nm (Hoppel minimum). While for one of these two types the accumulation mode was dominating (albeit less so than for air masses advected from Africa), the Aitken mode dominated the other and contributed more than 50 % of all particles. These Aitken mode particles likely were formed by new particle formation no more than 3 days prior to the measurements. Hygroscopicity of particles in the CCN size range was determined from CCN measurements to be κ = 0.66 on average, which suggests that these particles contain mainly sulfate and do not show a strong influence from organic material, which might generally be the case for the months during which measurements were made. The average κ could be used to derive N CCN from measured number size distributions, showing that this is a valid approach to obtain N CCN . Although the total particulate mass sampled on filters was found to be dominated by Na + and Cl − , this was found to be contributed by a small number of large particles (> 500 nm, mostly even in the super-micron size range). Based on a three-modal fit, a sea spray mode observed in the NSDs was found to contribute 90 % to the total particulate mass but only 4 to 10 % to N total and up to 15 % to N CCN . This is in accordance with finding no correlation between N total and wind speed.

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“…Again the R values and R pattern were nearly identical when differential PCASP particle concentrations were considered. Figure 1a also displays the R pattern for CCN concentrations (N CCN here at 1% S so N 1% ) measured by the DRI CCN spectrometers (Hudson 1989) as presented by Hudson and Mishra (2007) and hereafter H9) with cumulative PCASP and FSSP concentrations larger than the various threshold sizes. Only the smallest particles measured by the PCASP show a correlation with N 1%, and this is the only ambient particle size range that is uncorrelated with U.…”

Section: Resultsmentioning

confidence: 99%

On the relative role of sea salt cloud condensation nuclei (CCN)

2011

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Contrasts between cloud condensation nuclei (CCN) spectral volatility (thermal fractionation) measurements in two aircraft field projects provide insight into the relative contribution of sea salt. During the much more cloudy Rain in Cumulus over the Ocean (RICO) project there was a high correlation coefficient (R) between refractory (non-volatile) CCN concentrations (N CCN ) and horizontal wind speed (U), especially for low supersaturation (S) N CCN , whereas this R was significantly lower in the nearly cloud free Pacific Aerosol Sulfur Experiment (PASE) project. Volatile N CCN at all S were uncorrelated with U. Ambient particle concentrations over a broad range of large sizes displayed consistently high R with U in both projects that was similar to the R of refractory N CCN with U in RICO. The size range of this high R extended down to 0.2 μm in RICO but only down to 9 μm in PASE. In both projects particle concentrations smaller than these respective sizes were highly correlated with N CCN , at all S in PASE, but mainly with N CCN at high S in RICO. In each project N CCN at all S was uncorrelated with all ambient particle concentrations larger than these same respective sizes. N CCN at all S was also uncorrelated with U in both projects. The contrast in cloudiness between the two projects was responsible for many of the differences noted between the two projects. The results indicate that the effects of clouds on N CCN play a major role in the relative influence of sea salt on N CCN and ultimately on climate. Sea salt is a minor component of maritime CCN except at high wind speeds especially at low S.

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Relationships between CCN and cloud microphysics variations in clean maritime air

Cited by 57 publications

References 12 publications

The production of warm rain in shallow maritime cumulus clouds

The production of warm rain in shallow maritime cumulus clouds

Aerosol arriving on the Caribbean island of Barbados: physical properties and origin

On the relative role of sea salt cloud condensation nuclei (CCN)

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