Ship-produced cloud lines of 13 July 1991

Hindman, Edward E.; Porch, W.M.; Hudson, James G.; Durkee, Philip A.

doi:10.1016/1352-2310(94)00171-g

Cited by 23 publications

(15 citation statements)

References 17 publications

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“…The average near‐cloud‐base N CCN at 1% S of 19 cm −3 (Table 1) for the wintertime Southern Ocean baseline conditions is one of the lowest recorded [e.g., Hindman et al , 1994]. Surface N CCN at Cape Grim for the same month (July) during 1981–1991 were ∼70 cm −3 and 45 cm −3 for 1.2% and 0.23% S, respectively [ Ayers and Gras , 1991; Boers et al , 1994].…”

Section: Discussion and Comparisons With Previous Studiesmentioning

confidence: 99%

Wintertime/summertime contrasts of cloud condensation nuclei and cloud microphysics over the Southern Ocean

Yum

Hudson

2004

J. Geophys. Res.

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[1] Wintertime/summertime contrasts of cloud condensation nuclei (CCN) and cloud microphysics observed in clean maritime environments off the west coast of Tasmania, Australia in the Southern Ocean Cloud Experiment, are presented. The average wintertime CCN concentration (N CCN ) was 32 cm À3 at 1% supersaturation (S), but it was 19 cm À3 when only baseline (maritime airflow with minimal anthropogenic influences) flights were considered. In contrast, the average summertime N CCN were more than a factor of 5 higher than wintertime for all S ranges. The seasonal contrast was larger when only baseline flights were considered, especially at lower S: summertime more than an order of magnitude higher than wintertime at S below 0.1%. ). This difference was nearly a factor of 3 when only baseline flights were considered (57 cm À3 versus 20 cm À3 ). Flight-average N CCN and various representations of adiabatic cloud droplet concentrations (N a ) generally showed good correlations, indicating that the original effects of CCN are somehow retained in the N c (ave). The average mean diameter (MD) of the cloud droplets was 13.9 and 17.1 mm for the summer and winter clouds, respectively. For baseline only, average MDs were 15.4 and 18.2 mm, respectively. Average MD was thus above or close to the 15-mm threshold for drizzle production, except for the summertime nonbaseline clouds, which had an average MD smaller than 10 mm. Because of the larger droplet sizes, conversion to drizzle was more efficient in the winter clouds, where the average drizzle liquid water content (L d ) of 0.12 g m À3 was twice that of the summer L d . The L d for the summer nonbaseline clouds was negligible. Average L d was also highly dependent on cloud depth. Winter baseline clouds were sometimes too thin to produce significant drizzle even though they contained very low N c and very large MDs. The thickest clouds contained the highest L d although their MD was not always the largest.

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Section: Discussion and Comparisons With Previous Studiesmentioning

confidence: 99%

Wintertime/summertime contrasts of cloud condensation nuclei and cloud microphysics over the Southern Ocean

Yum

Hudson

2004

J. Geophys. Res.

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“…Another case of interest involves a rift area sampled by an instrumented ship in the eastern Pacific (Hindman et al 1994). CCN concentrations measured in this area were Ͻ10 cm Ϫ3 .…”

Section: Discussionmentioning

confidence: 99%

Aerosol and Cloud Microphysical Characteristics of Rifts and Gradients in Maritime Stratocumulus Clouds

Sharon

Albrecht

Jonsson³

et al. 2006

Journal of the Atmospheric Sciences

113

123

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A cloud rift is characterized as a large-scale, persistent area of broken, low-reflectivity stratocumulus clouds usually surrounded by a solid deck of stratocumulus. A rift observed off the coast of California was investigated using an instrumented aircraft to compare the aerosol, cloud microphysical, and thermodynamic properties in the rift with those of the surrounding solid stratocumulus deck. The microphysical characteristics in the solid stratocumulus deck differ substantially from those of a broken, cellular rift where cloud droplet concentrations are a factor of 2 lower than those in the solid cloud. Furthermore, cloud condensation nuclei (CCN) concentrations were found to be about 3 times greater in the solid-cloud area compared with those in the rift. Although drizzle was observed near cloud top in parts of the solid stratocumulus cloud, the largest drizzle rates were associated with the broken clouds within the rift area and with extremely large effective droplet sizes retrieved from satellite data. Minimal thermodynamic differences between the rift and solid cloud deck were observed. In addition to marked differences in particle concentrations, evidence of a mesoscale circulation near the solid cloud-rift boundary is presented. This mesoscale circulation may provide a mechanism for maintaining a rift, but further study is required to understand the initiation of a rift and the conditions that may cause it to fill. A review of results from previous studies indicates similar microphysical characteristics in rift features sampled serendipitously. These observations indicate that cloud rifts are depleted of aerosols through the cleansing associated with drizzle and are a manifestation of natural processes occurring in marine stratocumulus.

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“…Radke et al [1989] and King et al [1993] described in situ and remote sensing measurements of two ship tracks off the California coast, which were obtained in the process of conducting other cloud studies. Other observations [Hindman et al, 1994] have been published, but these do not include in situ measurements. In this paper we describe an extensive series of in situ measurements from an aircraft of two ship tracks off the coast of Washington.…”

Section: Introductionmentioning

confidence: 99%

Measurements of ship‐induced tracks in clouds off the Washington coast

Ferek¹,

Hegg²,

Hobbs³

et al. 1998

J. Geophys. Res.

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Abstract. In situ cloud microphysical measurements are presented for two ship tracks detected off the Washington coast in three successive satellite images from the advanced very high resolution radiometer (AVHRR) channel 3 (3.7 gm). Aerosol and cloud water chemical data suggest that the tracks were produced by effluents from ship stacks. Cloud droplet spectra measured in the ship tracks had effective radii about one half of those measured in the ambient clouds. A drizzle mode was present in the ambient cloud, but this was largely suppressed in the ship tracks. Analysis of cloud condensation nucleus (CCN) and total particle spectra in and around the ship tracks suggest that the stability of the tracks could have been due to a feedback between the lowering of CCN concentrations as the ship plumes diluted, consequent increases in peak supersaturations in the cloud, and a modest amount of particle growth by gas-to-particle conversion.

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Ship-produced cloud lines of 13 July 1991

Cited by 23 publications

References 17 publications

Wintertime/summertime contrasts of cloud condensation nuclei and cloud microphysics over the Southern Ocean

Wintertime/summertime contrasts of cloud condensation nuclei and cloud microphysics over the Southern Ocean

Aerosol and Cloud Microphysical Characteristics of Rifts and Gradients in Maritime Stratocumulus Clouds

Measurements of ship‐induced tracks in clouds off the Washington coast

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