Shallow Cumulus Mixing and Subcloud-Layer Responses to Variations in Aerosol Loading

Seigel, R. B.

doi:10.1175/jas-d-13-0352.1

Cited by 30 publications

(53 citation statements)

References 105 publications

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“…3a) increases with the increase in aerosol loading, in agreement with previous studies (Saleeby et al, 2015;Seigel, 2014). This indicates an increase in the latent heat contribution to the cloud buoyancy, driven by an increase in the condensation efficiency (Dagan et al, 2015a, b;Koren et al, 2014;Pinsky et al, 2013;Seiki and Nakajima, 2014) (Figs.…”

Section: Mean Cloud Field Properties Under Different Aerosol Loading supporting

confidence: 90%

“…1c) that decreases above an aerosol loading of 25 cm −3 . Thus, for the more polluted simulations, the mass is distributed on smaller horizontal cloud areas, as shown in previous studies (Seigel, 2014).…”

Section: Mean Cloud Field Properties Under Different Aerosol Loading supporting

confidence: 78%

“…Jiang et al (2010) found a non-monotonic change in the derivative of the surface rain rate with aerosol loading (susceptibility) for higher maximal LWP clouds but a monotonic decrease in the total precipitation with aerosol loading. Seigel (2014) showed that cloud size decreases with aerosol loading due to enhanced entrainment at the cloud margins.…”

Section: Introductionmentioning

confidence: 99%

“…The organization of the field is influenced by cloud processes as well. Enhanced evaporative cooling in the sub-cloud layer, for example, can produce cold pools which enhance the generation of clouds only at their boundaries and hence change the organization of the field (Seigel, 2014;Seifert and Heus, 2013;Heiblum et al, 2016a).…”

Section: Introductionmentioning

confidence: 99%

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Time-dependent, non-monotonic response of warm convective cloud fields to changes in aerosol loading

et al. 2017

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Abstract. Large eddy simulations (LESs) with bin microphysics are used here to study cloud fields' sensitivity to changes in aerosol loading and the time evolution of this response. Similarly to the known response of a single cloud, we show that the mean field properties change in a nonmonotonic trend, with an optimum aerosol concentration for which the field reaches its maximal water mass or rain yield. This trend is a result of competition between processes that encourage cloud development versus those that suppress it. However, another layer of complexity is added when considering clouds' impact on the field's thermodynamic properties and how this is dependent on aerosol loading. Under polluted conditions, rain is suppressed and the non-precipitating clouds act to increase atmospheric instability. This results in warming of the lower part of the cloudy layer (in which there is net condensation) and cooling of the upper part (net evaporation). Evaporation at the upper part of the cloudy layer in the polluted simulations raises humidity at these levels and thus amplifies the development of the next generation of clouds (preconditioning effect). On the other hand, under clean conditions, the precipitating clouds drive net warming of the cloudy layer and net cooling of the sub-cloud layer due to rain evaporation. These two effects act to stabilize the atmospheric boundary layer with time (consumption of the instability). The evolution of the field's thermodynamic properties affects the cloud properties in return, as shown by the migration of the optimal aerosol concentration toward higher values.

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Section: Mean Cloud Field Properties Under Different Aerosol Loading supporting

confidence: 90%

Section: Mean Cloud Field Properties Under Different Aerosol Loading supporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Time-dependent, non-monotonic response of warm convective cloud fields to changes in aerosol loading

et al. 2017

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“…Clouds impacts on their environment are also clearly evident below their bases, as evaporative cooling of rain28 can produce cold pools near the surface that can change the organization of the field1646. On the one hand, convective thermals originating within these cold pools have a reduced likelihood of reaching the lifting condensation level (LCL) and forming new clouds.…”

mentioning

confidence: 99%

Aerosol effect on the evolution of the thermodynamic properties of warm convective cloud fields

Dagan

Koren

Altaratz

et al. 2016

Sci Rep

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Convective cloud formation and evolution strongly depend on environmental temperature and humidity profiles. The forming clouds change the profiles that created them by redistributing heat and moisture. Here we show that the evolution of the field’s thermodynamic properties depends heavily on the concentration of aerosol, liquid or solid particles suspended in the atmosphere. Under polluted conditions, rain formation is suppressed and the non-precipitating clouds act to warm the lower part of the cloudy layer (where there is net condensation) and cool and moisten the upper part of the cloudy layer (where there is net evaporation), thereby destabilizing the layer. Under clean conditions, precipitation causes net warming of the cloudy layer and net cooling of the sub-cloud layer (driven by rain evaporation), which together act to stabilize the atmosphere with time. Previous studies have examined different aspects of the effects of clouds on their environment. Here, we offer a complete analysis of the cloudy atmosphere, spanning the aerosol effect from instability-consumption to enhancement, below, inside and above warm clouds, showing the temporal evolution of the effects. We propose a direct measure for the magnitude and sign of the aerosol effect on thermodynamic instability.

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Characterization of cumulus cloud fields using trajectories in the center of gravity versus water mass phase space: 2. Aerosol effects on warm convective clouds

et al. 2016

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In Part I of this work a 3‐D cloud tracking algorithm and phase space of center of gravity altitude versus cloud liquid water mass (CvM space) were introduced and described in detail. We showed how new physical insight can be gained by following cloud trajectories in the CvM space. Here this approach is used to investigate aerosol effects on cloud fields of warm cumuli. We show a clear effect of the aerosol loading on the shape and size of CvM clusters. We also find fundamental differences in the CvM space between simulations using bin versus bulk microphysical schemes, with the bin scheme precipitation expressing much higher sensitivity to changes in aerosol concentrations. Using the bin microphysical scheme, we find that the increase in cloud center of gravity altitude with increase in aerosol concentrations occurs for a wide range of cloud sizes. This is attributed to reduced sedimentation, increased buoyancy and vertical velocities, and increased environmental instability, all of which are tightly coupled to inhibition of precipitation processes and subsequent feedbacks of clouds on their environment. Many of the physical processes shown here are consistent with processes typically associated with cloud invigoration.

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Shallow Cumulus Mixing and Subcloud-Layer Responses to Variations in Aerosol Loading

Cited by 30 publications

References 105 publications

Time-dependent, non-monotonic response of warm convective cloud fields to changes in aerosol loading

Time-dependent, non-monotonic response of warm convective cloud fields to changes in aerosol loading

Aerosol effect on the evolution of the thermodynamic properties of warm convective cloud fields

Characterization of cumulus cloud fields using trajectories in the center of gravity versus water mass phase space: 2. Aerosol effects on warm convective clouds

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