A New Heuristic Lagrangian Marine Boundary Layer Cloud Model

Abstract A new heuristic model of stratocumulus cloudiness in the inversion-capped marine boundary layer is developed and tested. The essential ingredient is a new method for predicting the statistical distribution of temperature and specific humidity at the inversion base under partially decoupled conditions along steady-state marine boundary layer (MBL) trajectories. MBL decoupling is parameterized as an increasing function of the height difference between the inversion base and lifting condensation level (LCL) of the mixed-layer air. Required inputs are sea surface temperature (SST), free air (above inversion) temperature and humidity, subsidence velocity, and mean boundary layer wind speed. Upstream boundary conditions must also be specified but have little influence at sufficient downstream distances (>2000 km). The model is applied to the cold advection regime of the northeastern subtropical Pacific and to both warm and cold advection regimes of the eastern equatorial Pacific Ocean. The model is conceptually simple and avoids explicit calculation of several important physical processes. Nevertheless, it is at least qualitatively successful in predicting both the climatological mean properties and climate anomaly variations of MBL stratocumulus in both regions. These results suggest that, regardless of other properties, successful MBL stratocumulus models will need to accurately predict inversion base height and the LCL and they will have to account for downstream memory effects.

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Galápagos upwelling driven by localized wind–front interactions

Scientific Reports ◽

10.1038/s41598-020-80609-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Alexander Forryan ◽

Alberto C. Naveira Garabato ◽

Clément Vic ◽

A. J. George Nurser ◽

Alexander R. Hearn

Keyword(s):

Ocean Circulation ◽

Realistic Model ◽

Surface Mixed Layer ◽

Equatorial Pacific Ocean ◽

World Heritage Sites ◽

Theory Of Evolution ◽

Heritage Sites ◽

Galapagos Archipelago ◽

Eastern Equatorial Pacific ◽

Eastern Equatorial Pacific Ocean

AbstractThe Galápagos archipelago, rising from the eastern equatorial Pacific Ocean some 900 km off the South American mainland, hosts an iconic and globally significant biological hotspot. The islands are renowned for their unique wealth of endemic species, which inspired Charles Darwin’s theory of evolution and today underpins one of the largest UNESCO World Heritage Sites and Marine Reserves on Earth. The regional ecosystem is sustained by strongly seasonal oceanic upwelling events—upward surges of cool, nutrient-rich deep waters that fuel the growth of the phytoplankton upon which the entire ecosystem thrives. Yet despite its critical life-supporting role, the upwelling’s controlling factors remain undetermined. Here, we use a realistic model of the regional ocean circulation to show that the intensity of upwelling is governed by local northward winds, which generate vigorous submesoscale circulations at upper-ocean fronts to the west of the islands. These submesoscale flows drive upwelling of interior waters into the surface mixed layer. Our findings thus demonstrate that Galápagos upwelling is controlled by highly localized atmosphere–ocean interactions, and call for a focus on these processes in assessing and mitigating the regional ecosystem’s vulnerability to 21st-century climate change.

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Tectonic processes in Papua New Guinea and past productivity in the eastern equatorial Pacific Ocean

Nature ◽

10.1038/19281 ◽

1999 ◽

Vol 398 (6728) ◽

pp. 601-604 ◽

Cited By ~ 68

Author(s):

Mark. L. Wells ◽

Geoffrey K. Vallis ◽

Eli A. Silver

Keyword(s):

Pacific Ocean ◽

Papua New Guinea ◽

New Guinea ◽

Equatorial Pacific ◽

Equatorial Pacific Ocean ◽

Tectonic Processes ◽

Eastern Equatorial Pacific ◽

Eastern Equatorial Pacific Ocean

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Marine boundary layer cloud regimes and POC formation in a CRM coupled to a bulk aerosol scheme

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-12549-2013 ◽

2013 ◽

Vol 13 (24) ◽

pp. 12549-12572 ◽

Cited By ~ 40

Author(s):

A. H. Berner ◽

C. S. Bretherton ◽

R. Wood ◽

A. Muhlbauer

Keyword(s):

Boundary Layer ◽

Marine Boundary Layer ◽

Three Dimensional ◽

Two Dimensional ◽

State Variables ◽

Liquid Water Path ◽

Modeling Framework ◽

Boundary Layer Cloud ◽

Cloud Regimes ◽

Layer Cloud

Abstract. A cloud-resolving model (CRM) coupled to a new intermediate-complexity bulk aerosol scheme is used to study aerosol–boundary-layer–cloud–precipitation interactions and the development of pockets of open cells (POCs) in subtropical stratocumulus cloud layers. The aerosol scheme prognoses mass and number concentration of a single lognormal accumulation mode with surface and entrainment sources, evolving subject to processing of activated aerosol and scavenging of dry aerosol by clouds and rain. The CRM with the aerosol scheme is applied to a range of steadily forced cases idealized from a well-observed POC. The long-term system evolution is explored with extended two-dimensional (2-D) simulations of up to 20 days, mostly with diurnally averaged insolation and 24 km wide domains, and one 10 day three-dimensional (3-D) simulation. Both 2-D and 3-D simulations support the Baker–Charlson hypothesis of two distinct aerosol–cloud "regimes" (deep/high-aerosol/non-drizzling and shallow/low-aerosol/drizzling) that persist for days; transitions between these regimes, driven by either precipitation scavenging or aerosol entrainment from the free-troposphere (FT), occur on a timescale of ten hours. The system is analyzed using a two-dimensional phase plane with inversion height and boundary layer average aerosol concentrations as state variables; depending on the specified subsidence rate and availability of FT aerosol, these regimes are either stable equilibria or distinct legs of a slow limit cycle. The same steadily forced modeling framework is applied to the coupled development and evolution of a POC and the surrounding overcast boundary layer in a larger 192 km wide domain. An initial 50% aerosol reduction is applied to half of the model domain. This has little effect until the stratocumulus thickens enough to drizzle, at which time the low-aerosol portion transitions into open-cell convection, forming a POC. Reduced entrainment in the POC induces a negative feedback between the areal fraction covered by the POC and boundary layer depth changes. This stabilizes the system by controlling liquid water path and precipitation sinks of aerosol number in the overcast region, while also preventing boundary layer collapse within the POC, allowing the POC and overcast to coexist indefinitely in a quasi-steady equilibrium.

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Textural Variations of Calcareous Coarse Fractions in the Panama Basin (Eastern Equatorial Pacific Ocean)

The Fate of Fossil Fuel CO2 in the Oceans ◽

10.1007/978-1-4899-5016-1_34 ◽

1977 ◽

pp. 673-692 ◽

Cited By ~ 4

Author(s):

Jörn Thiede

Keyword(s):

Pacific Ocean ◽

Equatorial Pacific ◽

Equatorial Pacific Ocean ◽

Eastern Equatorial Pacific ◽

Eastern Equatorial Pacific Ocean

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Contrasting characteristics of open- and closed- cellular stratocumulus cloud in the Eastern North Atlantic

10.5194/acp-2021-63 ◽

2021 ◽

Author(s):

Michael P. Jensen ◽

Virendra P. Ghate ◽

Dié Wang ◽

Diana K. Apoznanski ◽

Mary J. Bartholomew ◽

...

Keyword(s):

Boundary Layer ◽

North Atlantic ◽

Large Scale ◽

Marine Boundary Layer ◽

Open Cell ◽

Cold Air ◽

Closed Cell ◽

Boundary Layer Cloud ◽

Eastern North Atlantic ◽

Layer Cloud

Abstract. Extensive regions of marine boundary layer cloud impact the radiative balance through their significant shortwave albedo while having little impact on outgoing longwave radiation. Despite this importance, these cloud systems remain poorly represented in large-scale models due to difficulty in representing the processes that drive their lifecycle and coverage. In particular, the mesoscale organization, and cellular structure of marine boundary clouds has important implications for the subsequent cloud feedbacks. In this study, we use long-term (2013–2018) observations from the Atmospheric Radiation Measurement (ARM) Facility's Eastern North Atlantic (ENA) site on Graciosa Island, Azores, Portugal to identify cloud cases with open- or closed-cellular organization. More than 500 hours of each organization type are identified. The ARM observations are combined with reanalysis and satellite products to quantify the cloud, precipitation, aerosol, thermodynamic and large-scale synoptic characteristics associated with these cloud types. Our analysis shows that both cloud organization populations occur during similar sea surface temperature conditions, but the open-cell cases are distinguished by stronger cold-air advection and large-scale subsidence compared to the closed-cell cases, consistent with their formation during cold-air outbreaks. We also find that the open-cell cases were associated with deeper boundary layers, stronger low-level winds, and higher-rain rates compared to their closed-cell counterparts. Finally, raindrops with diameters larger than one millimeter were routinely recorded at the surface during both populations, with a higher number of large drops during the open-cellular cases. The similarities and differences noted herein provide important insights into the environmental and cloud characteristics during varying marine boundary layer cloud mesoscale organization and will be useful for the evaluation of model simulations for ENA marine clouds.

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Contrasting characteristics of open- and closed-cellular stratocumulus cloud in the eastern North Atlantic

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-14557-2021 ◽

2021 ◽

Vol 21 (19) ◽

pp. 14557-14571

Author(s):

Michael P. Jensen ◽

Virendra P. Ghate ◽

Dié Wang ◽

Diana K. Apoznanski ◽

Mary J. Bartholomew ◽

...

Keyword(s):

Boundary Layer ◽

North Atlantic ◽

Large Scale ◽

Marine Boundary Layer ◽

Open Cell ◽

Cold Air ◽

Closed Cell ◽

Boundary Layer Cloud ◽

Eastern North Atlantic ◽

Layer Cloud

Abstract. Extensive regions of marine boundary layer cloud impact the radiative balance through their significant shortwave albedo while having little impact on outgoing longwave radiation. Despite this importance, these cloud systems remain poorly represented in large-scale models due to difficulty in representing the processes that drive their life cycle and coverage. In particular, the mesoscale organization and cellular structure of marine boundary clouds have important implications for the subsequent cloud feedbacks. In this study, we use long-term (2013–2018) observations from the Atmospheric Radiation Measurement (ARM) Facility's Eastern North Atlantic (ENA) site on Graciosa Island, Azores, Portugal, to identify cloud cases with open- or closed-cellular organization. More than 500 h of each organization type are identified. The ARM observations are combined with reanalysis and satellite products to quantify the cloud, precipitation, aerosol, thermodynamic, and large-scale synoptic characteristics associated with these cloud types. Our analysis shows that both cloud organization populations occur during similar sea surface temperature conditions, but the open-cell cases are distinguished by stronger cold-air advection and large-scale subsidence compared to the closed-cell cases, consistent with their formation during cold-air outbreaks. We also find that the open-cell cases were associated with deeper boundary layers, stronger low-level winds, and higher rain rates compared to their closed-cell counterparts. Finally, raindrops with diameters larger than 1 mm were routinely recorded at the surface during both populations, with a higher number of large drops during the open-cellular cases. The similarities and differences noted herein provide important insights into the environmental and cloud characteristics during varying marine boundary layer cloud mesoscale organization and will be useful for the evaluation of model simulations for ENA marine clouds.

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