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2. Potential impact of Aeroclipper observations targeting tropical cyclone in the Western Pacific.

Author

Hattori, Miki, Bellenger, Hugo, Duvel, Jean‐Philippe, and Enomoto, Takeshi

Abstract

The Aeroclipper is a new balloon device that can be attracted and captured by tropical cyclones (TC) and perform continuous in situ measurements at the air–sea interfaces. To estimate the potential effect of Aeroclipper observations on the analysis of TCs, virtual Aeroclipper observations targeting TC Haima (October 2016) were synthesized using an idealized surface pressure distribution and best track data and were assimilated using an ensemble data assimilation system. Results show that the assimilation of Aeroclipper measurements may provide a more accurate representation of the TC pressure, wind, and temperature in analyses. This also leads to improved precipitation around the Philippines. The ensemble spread shows that the Aeroclipper measurement assimilation has an impact on the analyses that extends into the tropics from the early stages of TC development. These impact signals propagate westward with easterly waves and eastward with large‐scale convective disturbances. Although the underlying mechanisms need to be further examined and tested using real Aeroclipper measurements, the present study shows that these balloons could provide valuable observations to improve the precision of analyses in presence of a TC. This is a first step toward a study of the impact of the Aeroclipper measurement on TC forecast. [ABSTRACT FROM AUTHOR]

Published
2024
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3. On the Mechanisms Driving Latent Heat Flux Variations in the Northwest Tropical Atlantic.

Author

Fernández, Pablo, Speich, Sabrina, Bellenger, Hugo, Lange Vega, Diego, Karstensen, Johannes, Zhang, Dongxiao, and Rocha, Cesar Barbedo

Subjects
LATENT heat, HEAT flux, OCEAN temperature, SEAWATER salinity, OCEAN-atmosphere interaction, OCEAN circulation
Abstract

The Northwest Tropical Atlantic (NWTA) is a region of complex surface ocean circulation. The most prominent feature is the North Brazil Current (NBC) and its retroflection at 8°N, which leads to the formation of numerous mesoscale eddies known as NBC rings. The NWTA also receives the outflow of the Amazon River, generating freshwater plumes that can extend up to 100,000 km2. We show that these two processes influence the spatial variability of the region's surface latent heat flux (LHF). On the one hand, the presence of surface freshwater modifies the vertical stratification of the ocean, the mixed layer heat budget, and thus the air‐sea heat exchanges. On the other hand, NBC rings create a highly heterogeneous mesoscale sea surface temperature (SST) field that directly influences the near‐surface atmospheric circulation. These effects are illustrated by observations from the ElUcidating the RolE of Cloud‐Circulation Coupling in ClimAte ‐ Ocean Atmosphere (EUREC4A‐OA) and Atlantic Tradewind Ocean‐Atmosphere Interaction Campaign (ATOMIC) experiments, satellite and reanalysis data. We decompose the LHF budget into several terms controlled by different atmospheric and oceanic processes to identify the mechanisms leading to LHF changes. We find LHF variations of up to 160 W m2, of which 100 W m2 are associated with wind speed changes and 40 W m2 with SST variations. Surface currents or heat release associated with stratification changes remain as second‐order contributions with LHF variations of less than 10 W m2 each. This study highlights the importance of considering these three components to properly characterize LHF variability at different spatial scales, although it is limited by the scarcity of collocated observations. Plain Language Summary: The Northwest Tropical Atlantic (NWTA) is a region with a complex ocean circulation. It is dominated by the North Brazil Current (NBC), which parallel to the South American coast and changes its direction at 8°N. This leads to the formation of closed swirling circulations known as NBC rings. The NWTA also receives the outflow of the Amazon River. These two features affect the heat exchange between the ocean and the atmosphere associated with water evaporation (latent heat flux, LHF) as they modify sea surface temperature, salinity and the near‐surface atmospheric circulation. Here, we use the observations collected from the ElUcidating the RolE of Cloud‐Circulation Coupling in ClimAte ‐ Ocean Atmosphere (EUREC4A‐OA) and Atlantic Tradewind Ocean‐Atmosphere Interaction Campaign (ATOMIC) experiments, satellite data and combined observations with models to identify the key mechanisms leading to such LHF variations. More of 60% of them are associated to surface winds whilst sea surface temperature is behind a 25%. The Amazon outflow accounts for less than 10%. Although this study is limited by the paucity of oceanic, atmospheric and air‐sea interface observations located at the same point in time and space, it highlights the importance of considering these three components to properly describe LHF variability. Key Points: Latent heat flux (LHF) presents strong spatial variations in the northwest tropical Atlantic (NWTA), which has a complex ocean circulationSurface winds and sea surface temperature are the major drivers of LHF changes. The Amazon plume remains as a second‐order contributorIt is necessary to distinguish between spatial scales (mesoscale and below vs. large‐scale) when assessing the ocean's influence on LHF [ABSTRACT FROM AUTHOR]

Published
2024
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4. Sensitivity of the Global Ocean Carbon Sink to the Ocean Skin in a Climate Model.

Author

Bellenger, Hugo, Bopp, Laurent, Ethé, Christian, Ho, David, Duvel, Jean Philippe, Flavoni, Simona, Guez, Lionel, Kataoka, Takahito, Perrot, Xavier, Parc, Laetitia, and Watanabe, Michio

Subjects
CARBON cycle, SEAWATER salinity, ATMOSPHERIC models, OCEAN, GLOBAL modeling systems, SKIN effect, CHEMICAL equilibrium
Abstract

The ocean skin is composed of thin interfacial microlayers of temperature and mass of less than 1 mm where heat and chemical exchanges are controlled by molecular diffusion. It is characterized by a cooling of ∼−0.2 K and an increase in salinity of ∼0.1 g/kg (absolute salinity) relative to the water below. A surface observation‐based air‐sea CO2 flux estimate considering the variation of the CO2 concentration in these microlayers has been shown to lead to an increase in the global ocean sink of the anthropogenic CO2 by +0.4 PgC yr−1 (15% of the global sink). This study analyzes this effect in more details using a 15‐year (2000–2014) simulation from an Earth System Model (ESM) that incorporates a physical representation of the ocean surface layers (diurnal warm layer and rain lenses) and microlayers. Results show that considering the microlayers increases the simulated global ocean carbon sink by +0.26 to +0.37 PgC yr−1 depending on assumptions on the chemical equilibrium. This is indeed about 15% of the global sink (2.04 PgC yr−1) simulated by the ESM. However, enabling the ocean skin adjustment to feedback on ocean carbon concentrations reduces this increase to only +0.13 (±0.09) PgC y−1. Coupled models underestimate the ocean carbon sink by ∼5% if the ocean skin effect is not included. Plain Language Summary: The ocean skin is a thin layer of less than a millimeter that is in contact with the atmosphere, where the heat and chemical exchanges are controlled by molecular diffusion. It typically corresponds to a temperature at the ocean interface that is cooler by −0.2 K than the water at a depth of a millimeter. It also corresponds to a salinity that is slightly higher at the interface. Taking into account these temperature and salinity changes in this thin layer can change calculations of the global ocean carbon sink substantially. We use a global Earth System Model including a representation of the ocean skin to study this impact. We found an increase of 15% in the simulated global ocean carbon sink. This is consistent with past studies. Enabling the flux to feedback on the ocean carbon concentration significantly reduces its impact. We conclude by discussing the uncertainties in the global ocean carbon sink associated with the formulation of the carbon flux and the representation of the ocean skin. Key Points: Considering the ocean skin increases the global ocean CO2 sink by +0.26 to +0.37 PgC yr−1 (∼15% for 2000–2014) in an Earth System ModelEnabling the ocean skin adjustment to feedback on ocean carbon concentrations dampens this increase to +0.13 PgC y−1 (∼5% for 2000–2014)This global adjustment depends on the CO2 flux formulation and ultimately on the model capacity to transfer CO2 into the ocean interior [ABSTRACT FROM AUTHOR]

Published
2023
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6. EUREC⁴A

Author

Stevens, Björn, Bony, Sandrine, Farrell, David, Ament, Felix, Blyth, Alan, Fairall, Christopher, Karstensen, Johannes, Quinn, Patricia K., Speich, Sabrina, Acquistapace, Claudia, Aemisegger, Franziska, Albright, Anna L., Bellenger, Hugo, Bodenschatz, Eberhard, Caesar, Kathy-Ann, Chewitt-Lucas, Rebecca, de Boer, Gijs, Delanoë, Julien, Denby, Leif, Ewald, Florian, and Villiger, Leonie

Abstract

The science guiding the EUREC4A campaign and its measurements is presented. EUREC4A comprised roughly 5 weeks of measurements in the downstream winter trades of the North Atlantic - eastward and southeastward of Barbados. Through its ability to characterize processes operating across a wide range of scales, EUREC4A marked a turning point in our ability to observationally study factors influencing clouds in the trades, how they will respond to warming, and their link to other components of the earth system, such as upper-ocean processes or the life cycle of particulate matter. This characterization was made possible by thousands (2500) of sondes distributed to measure circulations on meso- (200 km) and larger (500 km) scales, roughly 400 h of flight time by four heavily instrumented research aircraft; four global-class research vessels; an advanced ground-based cloud observatory; scores of autonomous observing platforms operating in the upper ocean (nearly 10 000 profiles), lower atmosphere (continuous profiling), and along the air-sea interface; a network of water stable isotopologue measurements; targeted tasking of satellite remote sensing; and modeling with a new generation of weather and climate models. In addition to providing an outline of the novel measurements and their composition into a unified and coordinated campaign, the six distinct scientific facets that EUREC4A explored - from North Brazil Current rings to turbulence-induced clustering of cloud droplets and its influence on warm-rain formation - are presented along with an overview of EUREC4A's outreach activities, environmental impact, and guidelines for scientific practice. Track data for all platforms are standardized and accessible at 10.25326/165 , and a film documenting the campaign is provided as a video supplement. ISSN:1866-3516 ISSN:1866-3508

Published
2021

8. Ship- And island-based atmospheric soundings from the 2020 EUREC4A field campaign

Author

Christine Stephan, Claudia, Schnitt, Sabrina, Schulz, Hauke, Bellenger, Hugo, De Szoeke, Simon P., Acquistapace, Claudia, Baier, Katharina, Dauhut, Thibaut, and Helfer, K.C.

Abstract

To advance the understanding of the interplay among clouds, convection, and circulation, and its role in climate change, the Elucidating the role of clouds-circulation coupling in climate campaign (EUREC4A) and Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC) collected measurements in the western tropical Atlantic during January and February 2020. Upper-air radiosondes were launched regularly (usually 4-hourly) from a network consisting of the Barbados Cloud Observatory (BCO) and four ships within 6-16°N, 51-60°W. From 8 January to 19 February, a total of 811 radiosondes measured wind, temperature, and relative humidity. In addition to the ascent, the descent was recorded for 82 % of the soundings. The soundings sampled changes in atmospheric pressure, winds, lifting condensation level, boundary layer depth, and vertical distribution of moisture associated with different ocean surface conditions, synoptic variability, and mesoscale convective organization. Raw (Level 0), quality-controlled 1 s (Level 1), and vertically gridded (Level 2) data in NetCDF (Stephan et al., 2020) are available to the public at AERIS (https://doi.org/10.25326/137 https://doi.org/10.25326/137). The methods of data collection and post-processing for the radiosonde data set are described here.

Published
2021

9. Ship- and island-based atmospheric soundings from the 2020 EUREC4A field campaign

Author

Stephan, Claudia Christine, Schnitt, Sabrina, Schulz, Hauke, Bellenger, Hugo, de Szoeke, Simon P., Acquistapace, Claudia, Baier, Katharina, Dauhut, Thibaut, Laxenaire, Rémi, Morfa-Avalos, Yanmichel, Person, Renaud, Quiñones Meléndez, Estefanía, Bagheri, Gholamhossein, Böck, Tobias, Daley, Alton, Güttler, Johannes, Helfer, Kevin C., Los, Sebastian A., Neuberger, Almuth, Röttenbacher, Johannes, Raeke, Andreas, Ringel, Maximilian, Ritschel, Markus, Sadoulet, Pauline, Schirmacher, Imke, Stolla, M. Katharina, Wright, Ethan, Charpentier, Benjamin, Doerenbecher, Alexis, Wilson, Richard, Jansen, Friedhelm, Kinne, Stefan, Reverdin, Gilles, Speich, Sabrina, Bony, Sandrine, Stevens, Bjorn, Max-Planck-Institut für Meteorologie (MPI-M), Max-Planck-Gesellschaft, Institut für Geophysik und Meteorologie [Köln], Universität zu Köln, Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), College of Earth, Ocean and Atmospheric Sciences [Corvallis] (CEOAS), Oregon State University (OSU), Center for Ocean-Atmospheric Prediction Studies (COAPS), Florida State University [Tallahassee] (FSU), Nucleus for European Modeling of the Ocean (NEMO R&D ), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU), Laboratory for Fluid Physics, Pattern Formation and Biocomplexity (LFPN), Max Planck Institute for Dynamics and Self-Organization (MPIDS), Max-Planck-Gesellschaft-Max-Planck-Gesellschaft, Caribbean Institute for Meteorology and Hydrology (CIMH), Max-Planck-Institut für Dynamik und Selbstorganisation (MPIDS), Department of Geoscience and Remote Sensing [Delft], Delft University of Technology (TU Delft), Department of Earth and Planetary Sciences [Albuquerque] (EPS), The University of New Mexico [Albuquerque], Leipziger Institut für Meteorologie (LIM), Universität Leipzig [Leipzig], Deutscher Wetterdienst [Offenbach] (DWD), Météo France, University of Hamburg, MeteoModem, Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), TROPO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Processus et interactions de fine échelle océanique (PROTEO), INSU-CNRS program LEFE, Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU), Centre National de la Recherche Scientifique (CNRS)-Météo France, Universität zu Köln = University of Cologne, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Universität Leipzig, Météo-France Direction Interrégionale Sud-Est (DIRSE), Météo-France, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and Météo France-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]
Abstract

To advance the understanding of the interplay among clouds, convection, and circulation, and its role in climate change, the Elucidating the role of clouds–circulation coupling in climate campaign (EUREC4A) and Atlantic Tradewind Ocean–Atmosphere Mesoscale Interaction Campaign (ATOMIC) collected measurements in the western tropical Atlantic during January and February 2020. Upper-air radiosondes were launched regularly (usually 4-hourly) from a network consisting of the Barbados Cloud Observatory (BCO) and four ships within 6–16∘ N, 51–60∘ W. From 8 January to 19 February, a total of 811 radiosondes measured wind, temperature, and relative humidity. In addition to the ascent, the descent was recorded for 82 % of the soundings. The soundings sampled changes in atmospheric pressure, winds, lifting condensation level, boundary layer depth, and vertical distribution of moisture associated with different ocean surface conditions, synoptic variability, and mesoscale convective organization. Raw (Level 0), quality-controlled 1 s (Level 1), and vertically gridded (Level 2) data in NetCDF format (Stephan et al., 2020) are available to the public at AERIS (https://doi.org/10.25326/137). The methods of data collection and post-processing for the radiosonde data set are described here.

Published
2021

10. The EUREC4A-Ocean/Atmosphere campaign: status

Author

Karstensen, Johannes, Speich, Sabrina, Renault, Lionel, Hervé, Giordani, Meroni, Agostino Niyonkuru, Pasquero, Claudia, Desbiolles, Fabien, Bellenger, Hugo, Bopp, Laurent, Lapeyre, Guillaume, Gentemann, Chelle, Zhang, Dongxiao, Laxenaire, R., Storch, Jin‐song, Reverdin, Gilles, Thompson, Elizabeth, Heywood, Karen J., Bourras, Denis, Thomson, James, Foltz, Gregory R., Branger, Hubert, Bigorre, Sebastien, Clayson, Carol, Sullivan, Peter P., Mcwilliams, James C., Zhang, Chidong, Rocha, Cesar, Acquistapace, Claudia, Fairall, Chris, Zuidema, Paquita, Horstmann, Jochen, Schütte, Florian, Olivier, Léa, L'Hegaret, Pierre, Carton, Xavier J., Rudloff, Daniel, Baranowski, Darek, Landschuetzer, Peter, Lange, Diego, Wulfmeyer, Volker, Behrendt, Andreas, Labbri, Giacomo, Farrell, David, Karstensen, J, Speich, S, Renault, L, Giordani, H, Meroni, A, Pasquero, C, Desbiolles, F, Bellenger, H, Bopp, L, Lapeyre, G, Gentemann, C, Zhang, D, Laxenaire, R, von Storch, J, Reverdin, G, Thompson, E, Heywood, K, Bourras, D, Thomson, J, Foltz, G, Hubert, B, Bigorre, S, Clayson, C, Sullivan, P, Mcwilliams, J, Zhang, C, Rocha, C, Acquistapace, C, Fairall, C, Zuidema, P, Horstmann, J, Schutte, F, Olivier, L, L'Hegaret, P, Carton, X, Rudloff, D, Baranowski, D, Landschuetzer, P, Lange, D, Wulfmeyer, V, Behrendt, A, Labbri, G, Farrell, D, Helmholtz Centre for Ocean Research [Kiel] (GEOMAR), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Department of Statistics, University of California Los Angeles, Los Angeles, CA, United States, affiliation inconnue, Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Università degli Studi di Milano-Bicocca = University of Milano-Bicocca (UNIMIB), Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), and Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, field campaign, tropical Atlantic, EUREC4A
Abstract

International audience; The ocean fine scale (from the mesoscale to the submesoscale) is susceptible to impact air-sea exchange and has an integral effect on the large scale atmosphere and ocean dynamics. Many recent advances in understanding underlying processes have been obtained from modeling efforts and only few in-situ observational studies exist one of them being the EUREC4A-OA/ATOMIC campaign that was added to the EUREC4A atmospheric campaign. This experiment took place in January-February 2020 in the Northwest Tropical Atlantic Ocean with the aim to collect synchronized ocean and atmosphere data to improve our understanding of the role of fine scale processes in the internal ocean dynamics and air-sea interaction.Four oceanographic vessels, coordinated with air-borne observations and autonomous ocean platforms (underwater gliders, Saildrones, drifters), simultaneously acquired ocean and atmosphere data east of the island of Barbados and further south, up to the border of French Giuana. This way, ocean and atmospheric data was acquired in two contrasting regions: (1) the Trade wind region and (2) a region filled with mesoscale eddies. Operations allowed investigating upper ocean processes from small to mesoscale and from sub-diurnal to monthly.A variety of mesoscale eddies were crossed with diverse characteristics, ranging from shallow cyclonic and anticyclonic eddies to the deep reaching structures. Some of these eddies, and in particular North Brazil Rings, have been previously observed and described in dedicated oceanographic experiments. Nonetheless, the EUREC4A-OA/ATOMIC campaign brings in new details about the vertical structure, the dynamics and the potential impact on air-sea interactions of these mesoscale features.With the various observing platforms it was possible to sample the upper-ocean in great detail, resolving frontal scales and stratification. For example, the remnants of the Amazon plume, flowing northward along the shelf-break and being advected far offshore though NBC rings, create a rich variety of submesoscale fronts and a strong barrier layer impacting air-sea exchange of heat and momentum. The ongoing analyses on the ocean dynamics regional and local structures and specifics of air-sea interaction will be highlighted in this presentation.

Published
2021

11. EUREC 4 A

Author

Stevens, Bjorn, Bony, Sandrine, Farrell, David, Ament, Felix, Blyth, Alan M., Fairall, Chiristopher W., Karstensen, Johannes, Quinn, Patricia K., Speich, Sabrina, Acquistapace, Claudia, Aemisegger, Franziska, Albright, Anna, Bellenger, Hugo, Bodenschatz, Eberhard, Caesar, Kathy-Ann, Chewitt-Lucas, Rebecca, De Boer, Gijs, Delanoë, Julien, Denby, Leif Christopher, Ewald, Florian, Fildier, Benjamin, Forde, Marvin, George, Geet, Gross, Silke, Hagen, Martin, Hausold, Andrea, Heywood, Karen J., Hirsch, Lutz, Jacob, Marek, Jansen, Friedhelm, Kinne, Stefan, Klocke, Daniel, Kölling, Tobias, Konow, Heike, Lothon, Marie, Mohr, Wiebke, Naumann, Ann Kristin, Nuijens, Louise, Olivier, Léa, Pincus, Robert, Pöhlker, Mira L., Reverdin, Gilles, Roberts, Gregory, Schnitt, Sabrina, Sullivan, Peter P., Touzé-Peiffer, Ludovic, Vial, Jessica, Vogel, Raphaela, Alexander, Nicola, Alves, Lyndon, Arixi, Sophian, Asmath, Hamish, Bagheri, Gholamhossein, Bailey, Adriana, Baranowski, Dariusz, Baron, Alexandre, Barrau, Sébastien, Barrett, Paul Alan, Behrendt, Andreas, Bendinger, Arne, Beucher, Florent, Bigorre, Sebastien, Bosser, Pierre, Blossey, P., Bock, Olivier, Bourras, Denis, Bouruet-Aubertot, Pascale, Bower, K, Branger, H, Brennek, M, Brewer, A, Brilouet, P.-E, Brügmann, B, Buehler, S, Burke, E, Burton, R, Böing, S, Calmer, R, Canonici, J.-C, Carton, X, Cato, G, Charles, J, Chazette, Patrick, Chen, Y, Choularton, T, Chuang, P, Clarke, S, Coe, H, Cornet, C, Coutris, P, Couvreux, F, Crewell, S, Cronin, T, Cui, Z, Cuypers, Y, Daley, A, Damerell, G, Dauhut, T, De Graaf, D, De Groot, G, De Szoeke, S, Deneke, H, Desbios, J.-P, Douet, V, Drushka, K, Dütsch, M, Ehrlich, A, Emanuel, K, Emmanouilidis, A, Etienne, J.-C, Etienne-Leblanc, S, Faure, G, Feingold, G, Ferrero, L, Fix, A, Flamant, Cyrille, Flatau, P, Foltz, G, Gadian, A, Galewsky, J, Gallagher, M, Gallimore, P, Gaston, C, Gentemann, C, Geyskens, N, Giez, A, Gourbeyre, C, Grosz, R, Gutleben, M, Güttler, J, Hall, K, Harris, G, Helfer, K, Henze, D, Herbert, C, Holanda, B, Ibanez-Landeta, A, Intrieri, J, Iyer, S, Julien, F, Kalesse, H, Kazil, J, Kellman, A, Kirchner, U, Klingebiel, M, Kremper, L, Kretzschmar, J, Krüger, O, Kurz, A, Körner, M, L'hégaret, P, Lachlan-Cope, T, Laing, A, Landschützer, P, Lang, T, Lange, D, Lange, I, Laplace, C, Laxenaire, R, Le Bihan, C, Leandro, M, Lefevre, N, Lenschow, D, Li, Q, Lloyd, G, Los, S, Losi, N, Lovell, O, Luneau, C, Makuch, P, Malinowski, S, Manta, G, Marinou, E, Marsden, N, Matthieu, L, Maury, N, Mayer, B, Mayers-Als, M, Mazel, Christophe, Mcgeary, W, Mcwilliams, J, Mech, M, Mehlmann, M, Meroni, A, Mieslinger, T, Minikin, A, Avalos, Y, Muller, Caroline, Musat, I, Möller, G, Napoli, A, Neuberger, A, Noone, D, Nordsiek, F, Nowak, J, Oswald, L, Parker, D, Peck, C, Person, R, Plueddemann, A, Pologne, L, Posyniak, M, Prange, M, Pöhlker, C, Pörtge, V, Pöschl, U, Quiñones Meléndez, E, Radtke, J, Ramage, K, Reimann, J, Renault, L, Reus, K, Reyes, A, Ribbe, J, Ringel, M, Ritschel, M, Rocha, C, Rochetin, N, Rollo, C, Röttenbacher, J, Saffin, L, Sandiford, S, Sandu, I, Schemann, V, Schirmacher, I, Schlenczek, O, Schmidt, J, Schröder, M, Schulz, H, Schwarzenboeck, A, Schäfer, M, Sealy, A, Serikov, I, Shohan, S, Siddle, E, Siebesma, A, Späth, F, Stephan, C, Stolla, M, Szkółka, W, Tarot, S, Tetoni, E, Thompson, E, Thomson, J, Tomassini, L, Totems, J, Villiger, L, Walther, A, Webber, B, Wendisch, M, Whitehall, S, Wiltshire, A, Wing, A, Wirth, M, Wiskandt, J, Wolf, K, Worbes, L, Wright, E, Wulfmeyer, V, Young, S, Zhang, D, Zhang, C, Ziemen, F, Zinner, T, Zuidema, P, Zöger, M, Max Planck Institute for Meteorology (MPI-M), Max-Planck-Gesellschaft, Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Caribbean Institute for Meteorology and Hydrology (CIMH), Meteorological Institute [Hamburg], University of Hamburg, National Centre for Atmospheric Science [Leeds] (NCAS), Natural Environment Research Council (NERC), NOAA Earth System Research Laboratory (ESRL), National Oceanic and Atmospheric Administration (NOAA), Helmholtz Centre for Ocean Research [Kiel] (GEOMAR), NOAA Pacific Marine Environmental Laboratory [Seattle] (PMEL), Institute for Geophysics and Meteorology [Köln] (IGM), University of Cologne, Institute for Atmospheric and Climate Science [Zürich] (IAC), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich), Max Planck Institute for Dynamics and Self-Organization (MPIDS), NOAA Physical Sciences Laboratory (PSL), SPACE - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), University of Leeds, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Deutscher Wetterdienst [Offenbach] (DWD), Ludwig-Maximilians-Universität München (LMU), Laboratoire d'aérologie (LA), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Universität Hamburg (UHH), Max Planck Institute for Marine Microbiology, Delft University of Technology (TU Delft), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Universität zu Köln, École nationale des sciences géographiques (ENSG), Institut National de l'Information Géographique et Forestière [IGN] (IGN)-Université Gustave Eiffel, Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), National Center for Atmospheric Research [Boulder] (NCAR), Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), TROPO - LATMOS, Institut Pythéas (OSU PYTHEAS), and Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)

Subjects
[SDE]Environmental Sciences, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2020

12. EUREC4A.

Author

Stevens, Bjorn, Bony, Sandrine, Farrell, David, Ament, Felix, Blyth, Alan, Fairall, Christopher, Karstensen, Johannes, K Quinn, Patricia, Speich, Sabrina, Acquistapace, Claudia, Aemisegger, Franziska, Lea Albright, Anna, Bellenger, Hugo, Bodenschatz, Eberhard, Caesar, Kathy-Ann, Chewitt-Lucas, Rebecca, de Boer, Gijs, Delanoë, Julien, Denby, Leif, and Ewald, Florian

Subjects
ATMOSPHERIC boundary layer, CLOUD droplets, RESEARCH vessels, PARTICULATE matter, ATMOSPHERIC models, OCEAN-atmosphere interaction
Abstract

The science guiding the EUREC4A campaign and its measurements are presented. EUREC4A comprised roughly five weeks of measurements in the downstream winter trades of the North Atlantic - eastward and south-eastward of Barbados. Through its ability to characterize processes operating across a wide range of scales, EUREC4A marked a turning point in our ability to observationally study factors influencing clouds in the trades, how they will respond to warming, and their link to other components of the earth system, such as upper-ocean processes or, or the life-cycle of particulate matter. This characterization was made possible by thousands (2500) of sondes distributed to measure circulations on meso (200 km) and larger (500 km) scales, roughly four hundred hours of flight time by four heavily instrumented research aircraft, four global-ocean class research vessels, an advanced ground-based cloud observatory, a flotilla of autonomous or tethered measurement devices operating in the upper ocean (nearly 10000 profiles), lower atmosphere (continuous profiling), and along the air-sea interface, a network of water stable isotopologue measurements, complemented by special programmes of satellite remote sensing and modeling with a new generation of weather/climate models. In addition to providing an outline of the novel measurements and their composition into a unified and coordinated campaign, the six distinct scientific facets that EUREC4A explored - from Brazil Ring Current Eddies to turbulence induced clustering of cloud droplets and its influence on warm-rain formation - are presented along with an overview EUREC4A's outreach activities, environmental impact, and guidelines for scientific practice. [ABSTRACT FROM AUTHOR]

Published
2021
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13. Ship- and island-based atmospheric soundings from the 2020 EUREC4A field campaign.

Author

Stephan, Claudia Christine, Schnitt, Sabrina, Schulz, Hauke, Bellenger, Hugo, de Szoeke, Simon P., Acquistapace, Claudia, Baier, Katharina, Dauhut, Thibaut, Laxenaire, Rémi, Morfa-Avalos, Yanmichel, Person, Renaud, Quiñones Meléndez, Estefanía, Bagheri, Gholamhossein, Böck, Tobias, Daley, Alton, Güttler, Johannes, Helfer, Kevin C., Los, Sebastian A., Neuberger, Almuth, and Röttenbacher, Johannes

Abstract

To advance the understanding of the interplay among clouds, convection, and circulation, and its role in climate change, the EUREC4A and ATOMIC field campaigns collected measurements in the western tropical Atlantic during January and February 2020. Upper-air radiosondes were launched regularly (usually 4-hourly) from a network consisting of the Barbados Cloud Observatory (BCO) and four ships within 51-60° W, 6-16° N. From January 8 to February 19, a total of 812 radiosondes measured wind, temperature and relative humidity. In addition to the ascent, the descent was recorded for 82 % of the soundings. The soundings sampled changes in atmospheric pressure, winds, lifting condensation level, boundary layer depth, and vertical distribution of moisture associated with different ocean surface conditions, synoptic variability, and mesoscale convective organization. Raw (Level-0), quality-controlled 1-second (Level-1), and vertically gridded (Level-2) data in NetCDF format (Stephan et al., 2020) are available to the public at AERIS (https://doi.org/10.25326/62). The methods of data collection and post-processing for the radiosonde data set are described here. [ABSTRACT FROM AUTHOR]

Published
2020
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16. The event-to-event variability of the boreal winter MJO

Author

Bellenger, Hugo, Duvel, Jean-Philippe, Variabilité climatique tropicale et globale (VARCLIM), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Département des Géosciences - ENS Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)

Subjects
[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]
Abstract

International audience; During boreal winters, perturbations of the convection by the Madden-Julian Oscillation (MJO) peak over three basins distributed in longitude south of the Equator: the eastern Indian Ocean (IO), the south of the Maritime Continent (MC) and the western Pacific Ocean (PO). We use the observed Outgoing Longwave Radiation (OLR) and low-level wind to identify and characterize all wintertime MJO events between 1979 and 2010. There is a large event-to-event variability with some MJO events organized at the planetary-scale having their amplitude well distributed over the 3 basins and some showing only basin-scale organization with a convective perturbation peaking over one or two basins. The average of the MJO amplitude for the three basins shows an intriguing decadal variability consistent for both OLR and low-level wind. The disparity between the 3 basins is dominated by an alternation between MJO amplitude peaking on either the Indian or the Pacific Ocean. This Indo-Pacific alternation, depicted by an Indo-Pacific Index (IPI), is partly related to ENSO. In El Niño conditions, there is not only an extension of the MJO perturbation further east, but also an increase of the MJO perturbation over the western Pacific and a diminution of the MJO perturbation over the eastern Indian Ocean.

Published
2012

19. Processes driving intraseasonal displacements of the eastern edge of the warm pool: the contribution of westerly wind events.

Author

Drushka, Kyla, Bellenger, Hugo, Guilyardi, Eric, Lengaigne, Matthieu, Vialard, Jérôme, and Madec, Gurvan

Subjects
*GENERAL circulation model, *SEA level, *HEAT flux, *OCEAN-atmosphere interaction, *OCEAN waves, *ADVECTION
Abstract

We investigate the processes responsible for the intraseasonal displacements of the eastern edge of the western Pacific warm pool (WPEE), which appear to play a role in the onset and development of El Niño events. We use 25 years of output from an ocean general circulation model experiment that is able to accurately capture the observed displacements of the WPEE, sea level anomalies, and upper ocean zonal currents at intraseasonal time scales in the western and central Pacific Ocean. Our results confirm that WPEE displacements driven by westerly wind events (WWEs) are largely controlled by zonal advection. This paper has also two novel findings: first, the zonal current anomalies responsible for the WPEE advection are driven primarily by local wind stress anomalies and not by intraseasonal wind-forced Kelvin waves as has been shown in most previous studies. Second, we find that intraseasonal WPEE fluctuations that are not related to WWEs are generally caused by intraseasonal variations in net heat flux, in contrast to interannual WPEE displacements that are largely driven by zonal advection. This study hence raises an interesting question: can surface heat flux-induced zonal WPEE motions contribute to El Niño-Southern Oscillation evolution, as WWEs have been shown to be able to do? [ABSTRACT FROM AUTHOR]

Published
2015
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21. Impact of Diurnal Warm Layers and Rain-Induced Cool Freshwater Lenses on Atmospheric boundary layer and convection : The CINDY/DYNAMO Case.

Author

Bellenger, Hugo, Perrot, Xavier, Duvel, Jean Philippe, Zhang, Yunyan, Xie, Shaocheng, and Guez, Lionel

Subjects
*GENERAL circulation model, *ATMOSPHERIC temperature, *THERMAL boundary layer, *ELECTRIC generators, *MADDEN-Julian oscillation, *SKIN temperature, *ATMOSPHERIC boundary layer
Abstract

Due to the lack of vertical mixing, shallow thermo-haline stable stratifications, corresponding to changes up to few degrees and several psu within the ocean first tens of centimeters, form when the wind is weak. These changes in skin temperature and salinity are induced by the absorption of solar radiation in the case of Diurnal Warm Layers (DWL) and by the addition of cool and fresh rainwater in the case of Cool Freshwater Lenses (CFL). By changing the ocean skin temperature, these phenomena can perturb the heat exchanges at the ocean interface and thus have an impact on the atmospheric boundary layer structure and on convection. In particular, DWL of 1 to 3°C are frequently observed in the deep tropics where they can destabilize the atmosphere and trigger convection in the afternoon. Less is known however about CFL characteristics and on their impact on atmosphere processes. The international CINDY/DYNAMO field campaign took place in the equatorial Indian Ocean in winter 2011-2012 to observe the complete lifecycle of Madden-Julian Oscillation (MJO) in the region where it usually originate. Three MJO events were documented. During this campaign, several large DWL and some CFL were observed from the R/V Revelle situated on the equator at 80°E. ECMWF analysis constrained by R/V Revelle precipitation radar measurements are used to derived large-scale forcing terms necessary to force single column models and limited area models. A single column version of the LMDZ atmospheric general circulation model coupled to a simple model for DWL and CFL is then used to study the impact of representing DWL and CFL. In particular, we will focus on their impact on the simulated atmospheric tendencies in temperature and moisture associated with different atmospheric processes: boundary layer turbulence, boundary layer thermals (shallow convection) and deep convection. [ABSTRACT FROM AUTHOR]

Published
2019

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