Statistics on the macrophysical properties of trade wind cumuli over the tropical western Atlantic

AbstractThe future change in equatorial upwelling between 1971–2000 and 2071–2100 is investigated using data from 24 coupled climate models. The multimodel ensemble (MME) mean exhibits substantial equatorial upwelling decrease in the eastern Pacific and weaker decrease in the western Atlantic Ocean. The MME mean of upwelling change and intermodel variation of that are decomposed into distinct isopycnal and diapycnal components. In the Pacific, the diapycnal upwelling decreases near the surface, associated with a weakened Ekman pumping. The isopycnal upwelling decreases at depths of 75–200 m around the core of the Equatorial Undercurrent (EUC) due to flattening of the density layer in which it flows. Both the weakened Ekman pumping and the EUC flattening are induced by the locally weakened trade wind over the eastern Pacific basin. In the equatorial Atlantic, both the change in MME mean and the intermodel variation of upwellings are significantly related to the weakened trade wind and enhanced stratification, although these drivers are not independent. The results for the Pacific Ocean imply that future reduction in upwelling may have impacts at different depths by different mechanisms. In particular, the rapid warming of sea surface temperature in the eastern Pacific basin may be mainly caused by the near-surface diapycnal upwelling reduction rather than isopycnal upwelling reduction associated EUC flattening, which is important at deeper levels.

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Cloud macrophysical properties from airborne observations during EUREC4A

10.5194/egusphere-egu2020-11106 ◽

2020 ◽

Author(s):

Heike Konow ◽

Marcus Klingebiel ◽

Felix Ament

Keyword(s):

Deep Convection ◽

Dry Season ◽

Trade Wind ◽

Special Focus ◽

Wet Season ◽

Diurnal Cycles ◽

Cloud Radar ◽

Wide Range ◽

Macrophysical Properties ◽

Different Response

Trade wind cumulus clouds are the predominant cloud type over the tropical Atlantic east of the island of Barbados. Parameters describing their macroscopic shape can help characterizing and comparing general features of clouds. This characterizing will indirectly help to constrain estimates of climate sensitivity, because models with different structures of trade wind cumuli feature different response to increased CO2 contents.Two aircraft campaigns with the HALO (High Altitude LOng range) aircraft took place in the recent past in this region: NARVAL-South (Next-generation Aircraft Remote-Sensing for VALidation studies) in December 2013, during the dry season, and NARVAL2 in August 2016, during the wet season. During these two campaigns, a wide range of cloud regimes from shallow to deep convection were sampled. This past observations are now extended with observations from this year&#8217;s measurement campaign EUREC4A, again during the dry season. EUREC4A is endorsed as WCRP capstone experiment and the synergy of four research aircraft, four research vessels and numerous additional observations will provide comprehensive characterizations of trade wind clouds and their environment.Part of the NARVAL payload on HALO is a 35 GHz cloud radar, which has been deployed on HALO on several missions since 2013. These cloud radar measurements are used to segment individual clouds entities by applying connected component analysis to the radar cloud mask. From these segmented individual clouds, macrophysical parameters are derived to characterize each individual cloud. This presentation will give an overview of the cloud macrophysics observed from HALO during EUREC4A. Typical macrophysical parameters, i.e. cloud depth, cloud length, cloud fraction, are analyzed. We will relate these to observations from past campaigns and assess the representativeness of EUREC4A. As special focus of the EUREC4A campaign, measurements will be performed during different times of the day to detect diurnal cycles. Macrophysical parameters can be used to characterize changes over the day and cloud scenes of similar clouds types can be identified.

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Dependence of mesoscale patterns of Trade-wind clouds on environmental conditions: an investigation using satellite and in-situ observations

10.5194/egusphere-egu2020-4622 ◽

2020 ◽

Author(s):

Sandrine Bony ◽

Hauke Schulz ◽

Jessica Vial ◽

Bjorn Stevens ◽

Keyword(s):

Meteorological Data ◽

Surface Wind ◽

Cloud Amount ◽

Surface Wind Speed ◽

Trade Wind ◽

Shallow Convection ◽

Western Atlantic ◽

Near Surface ◽

Cloud Patterns

Trade-wind clouds exhibit a large diversity of spatial organizations at the mesoscale. Over the tropical western Atlantic, a recent study has visually identified four prominent mesoscale patterns of shallow convection, referred to as Flowers, Fish, Gravel and Sugar. By using 19 years of satellite and meteorological data, we show that these four patterns can be identified objectively from satellite observations, and that on daily and interannual timescales, the near-surface wind speed and the strength of the lower-tropospheric stability discriminate the occurrence of the different organization patterns. Moreover, we point out a tight relationship between cloud patterns, low-level cloud amount and cloud-radiative effects. The EUREC4A field study taking place upwind of Barbados in Jan-Feb 2020 offers an opportunity to investigate these relationships from an in-situ and process-oriented perspective. Preliminary results will be discussed.

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Effect of Aerosol on the Susceptibility and Efficiency of Precipitation in Warm Trade Cumulus Clouds

Journal of the Atmospheric Sciences ◽

10.1175/2010jas3484.1 ◽

2010 ◽

Vol 67 (11) ◽

pp. 3525-3540 ◽

Cited By ~ 57

Author(s):

Hongli Jiang ◽

Graham Feingold ◽

Armin Sorooshian

Keyword(s):

Power Law ◽

Precipitation Rate ◽

Trade Wind ◽

Liquid Water Path ◽

Cumulus Clouds ◽

Scale Models ◽

Stratocumulus Clouds ◽

Power Law Function ◽

Macrophysical Properties ◽

Precipitating Clouds

Abstract Large-eddy simulations of warm, trade wind cumulus clouds are conducted for a range of aerosol conditions with a focus on precipitating clouds. Individual clouds are tracked over the course of their lifetimes. Precipitation rate decreases progressively as aerosol increases. For larger, precipitating clouds, the polluted clouds have longer lifetimes because of precipitation suppression. For clean aerosol conditions, there is good agreement between the average model precipitation rate and that calculated based on observed radar reflectivity Z and precipitation rate R relationships. Precipitation rate can be expressed as a power-law function of liquid water path (LWP) and Nd, to reasonable accuracy. The respective powers for LWP and Nd are of similar magnitude compared to those based on observational studies of stratocumulus clouds. The time-integrated precipitation rate represented by a power-law function of LWP, Nd, and cloud lifetime is much more reliably predicted than is R expressed in terms of LWP and Nd alone. The precipitation susceptibility (So = −dlnR/dlnNd) that quantifies the sensitivity of precipitation to changes in Nd depends strongly on LWP and exhibits nonmonotonic behavior with a maximum at intermediate LWP values. The relationship between So and precipitation efficiency is explored and the importance of including dependence on Nd in the latter is highlighted. The results provide trade cumulus cloud population statistics, as well as relationships between microphysical/macrophysical properties and precipitation, that are amenable for use in larger-scale models.

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Rain in Shallow Cumulus Over the Ocean: The RICO Campaign

Bulletin of the American Meteorological Society ◽

10.1175/bams-88-12-1912 ◽

2007 ◽

Vol 88 (12) ◽

pp. 1912-1928 ◽

Cited By ~ 268

Author(s):

Robert M. Rauber ◽

Bjorn Stevens ◽

Harry T. Ochs ◽

Charles Knight ◽

B. A. Albrecht ◽

...

Keyword(s):

Remote Sensing ◽

Trade Wind ◽

Western Atlantic ◽

Tropical Oceans ◽

Shallow Cumulus ◽

Weather And Climate ◽

Ensemble Statistics ◽

Research Aircraft ◽

Nearly Continuous ◽

Insight Into

Shallow, maritime cumuli are ubiquitous over much of the tropical oceans, and characterizing their properties is important to understanding weather and climate. The Rain in Cumulus over the Ocean (RICO) field campaign, which took place during November 2004–January 2005 in the trades over the western Atlantic, emphasized measurements of processes related to the formation of rain in shallow cumuli, and how rain subsequently modifies the structure and ensemble statistics of trade wind clouds. Eight weeks of nearly continuous S-band polarimetric radar sampling, 57 flights from three heavily instrumented research aircraft, and a suite of ground- and ship-based instrumentation provided data on trade wind clouds with unprecedented resolution. Observational strategies employed during RICO capitalized on the advances in remote sensing and other instrumentation to provide insight into processes that span a range of scales and that lie at the heart of questions relating to the cause and effects of rain from shallow maritime cumuli.

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The sensitivity of cloud radiative forcing with respect to the macrophysical properties and organization of the trade-wind cloud field during EUREC4A

10.5194/egusphere-egu21-2219 ◽

2021 ◽

Author(s):

Anna Luebke ◽

André Ehrlich ◽

Michael Schäfer ◽

Kevin Wolf ◽

Manfred Wendisch

Keyword(s):

Radiative Forcing ◽

Large Scale ◽

Global Climate ◽

Cloud Fraction ◽

Radiative Properties ◽

Trade Wind ◽

Liquid Water Path ◽

Cloud Radiative Forcing ◽

Flight Level ◽

Macrophysical Properties

The clouds in the Atlantic trade-wind region are known to have an important role in the global climate system, but the interactions between the microphysical, macrophysical and radiative properties of these clouds are complex. This work seeks to understand how the macrophysical properties and organization of the cloud field impact the large-scale cloud radiative forcing in order to provide the necessary information for the evaluation of the representation of these clouds in models. During the 2020 EUREC4A campaign, the German HALO aircraft was equipped for the first time with two instruments - the BACARDI instrument, a broadband radiometer that encompasses a set of pyrgeometers and pyranometers to measure the upward and downward solar and terrestrial radiation at flight level, and the VELOX Thermal IR imager. Simultaneously, one-minute resolution observations of the flight domain were obtained by the GOES-E satellite, thus providing information about the properties of the clouds on a spatial scale compatible with the large footprint of the BACARDI instrument. Using the products of these three instruments, we observe how the changing cloud field (e.g. cloud fraction, mean liquid water path (LWP), cloud top height, degree of clustering) in the EUREC4A domain impacts the radiation measured at flight level. We see that although cloud fraction plays a significant role as expected, it is not sufficient to parameterize the cloud radiative effects. Furthermore, the results indicate that the general organization of the cloud field as well as other properties describing the cloud population are necessary, but their relative importance varies between different cloud scenes.

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Occurrence and biogeographic significance of Heliaster (Echinodermata: Asteroidea) from the Pliocene of southwest Florida

Journal of Paleontology ◽

10.1017/s0022336000058960 ◽

1988 ◽

Vol 62 (01) ◽

pp. 126-132 ◽

Cited By ~ 8

Author(s):

Douglas S. Jones ◽

Roger W. Portell

Keyword(s):

Central American ◽

Eastern Pacific ◽

Whole Body ◽

Marine Fauna ◽

Western Atlantic ◽

Southwest Florida ◽

Extant Species ◽

Geologic Record ◽

Central American Isthmus

Whole body asteroid fossils are rare in the geologic record and previously unreported from the Cenozoic of Florida. However, specimens of the extant species,Heliaster microbrachiusXantus, were recently discovered in upper Pliocene deposits. This marks the first reported fossil occurrence of the monogeneric Heliasteridae, a group today confined to the eastern Pacific. This discovery provides further non-molluscan evidence of the close similarities between the Neogene marine fauna of Florida and the modern fauna of the eastern Pacific. The extinction of the heliasters in the western Atlantic is consistent with the pattern of many other marine groups in the region which suffered impoverishment following uplift of the Central American isthmus.

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