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3. Antarctic Ice Sheet paleo-constraint database

Author

Lecavalier, Benoit S., primary, Tarasov, Lev, additional, Balco, Greg, additional, Spector, Perry, additional, Hillenbrand, Claus-Dieter, additional, Buizert, Christo, additional, Ritz, Catherine, additional, Leduc-Leballeur, Marion, additional, Mulvaney, Robert, additional, Whitehouse, Pippa L., additional, Bentley, Michael J., additional, and Bamber, Jonathan, additional

Published
2023
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5. Ice Sheet and Sea Ice Ultrawideband Microwave radiometric Airborne eXperiment (ISSIUMAX) in Antarctica: first results from Terra Nova Bay

Author

Brogioni, Marco, Andrews, Mark J, Urbini, Stefano, Jezek, Kenneth C, Johnson, Joel T, Leduc-Leballeur, Marion, Macelloni, Giovanni, Ackley, Stephen F, Bringer, Alexandra, Brucker, Ludovic, Demir, Oguz, Fontanelli, Giacomo, Yardim, Caglar, Kaleschke, Lars, Montomoli, Francesco, Tsang, Leung, Becagli, Silvia, Frezzotti, Massimo, Brogioni, Marco, Andrews, Mark J, Urbini, Stefano, Jezek, Kenneth C, Johnson, Joel T, Leduc-Leballeur, Marion, Macelloni, Giovanni, Ackley, Stephen F, Bringer, Alexandra, Brucker, Ludovic, Demir, Oguz, Fontanelli, Giacomo, Yardim, Caglar, Kaleschke, Lars, Montomoli, Francesco, Tsang, Leung, Becagli, Silvia, and Frezzotti, Massimo

Abstract

An airborne microwave wide-band radiometer (500-2000 MHz) was operated for the first time in Antarctica to better understand the emission properties of sea ice, outlet glaciers and the interior ice sheet from Terra Nova Bay to Dome C. The different glaciological regimes were revealed to exhibit unique spectral signatures in this portion of the microwave spectrum. Generally, the brightness temperatures over a vertically homogeneous ice sheet are warmest at the lowest frequencies, consistent with models that predict that those channels sensed the deeper, warmer parts of the ice sheet. Vertical heterogeneities in the ice property profiles can alter this basic interpretation of the signal. Spectra along the lengths of outlet glaciers were modulated by the deposition and erosion of snow, driven by strong katabatic winds. Similar to previous experiments in Greenland, the brightness temperatures across the frequency band were low in crevasse areas. Variations in brightness temperature were consistent with spatial changes in sea ice type identified in satellite imagery and in situ ground-penetrating radar data. The results contribute to a better understanding of the utility of microwave wide-band radiometry for cryospheric studies and also advance knowledge of the important physics underlying existing L-band radiometers operating in space.

Published
2023

6. Antarctic Ice Sheet paleo-constraint database

Author

Lecavalier, Benoit S., Tarasov, Lev, Balco, Greg, Spector, Perry, Hillenbrand, Claus-Dieter, Buizert, Christo, Ritz, Catherine, Leduc-Leballeur, Marion, Mulvaney, Robert, Whitehouse, Pippa L., Bentley, Michael J., Bamber, Jonathan, Lecavalier, Benoit S., Tarasov, Lev, Balco, Greg, Spector, Perry, Hillenbrand, Claus-Dieter, Buizert, Christo, Ritz, Catherine, Leduc-Leballeur, Marion, Mulvaney, Robert, Whitehouse, Pippa L., Bentley, Michael J., and Bamber, Jonathan

Abstract

We present a database of observational constraints on past Antarctic Ice Sheet changes during the last glacial cycle intended to consolidate the observations that represent our understanding of past Antarctic changes and for state-space estimation and paleo-model calibrations. The database is a major expansion of the initial work of Briggs and Tarasov (2013). It includes new data types and multi-tier data quality assessment. The updated constraint database, AntICE2 (https://theghub.org/resources/4884, Lecavalier et al., 2022), consists of observations of past grounded- and floating-ice-sheet extent, past ice thickness, past relative sea level, borehole temperature profiles, and present-day bedrock displacement rates. In addition to paleo-observations, the present-day ice sheet geometry and surface ice velocities are incorporated to constrain the present-day ice sheet configuration. The method by which the data are curated using explicitly defined criteria is detailed. Moreover, the observational uncertainties are specified. The methodology by which the constraint database can be applied to evaluate a given ice sheet reconstruction is discussed. The implementation of the AntICE2 database for Antarctic Ice Sheet model calibrations will improve Antarctic Ice Sheet predictions during past warm and cold periods and yield more robust paleo-model spin ups for forecasting future ice sheet changes.

Published
2023

7. Extreme events of snow grain size increase in East Antarctica and their relationship with meteorological conditions.

Author

Stefanini, Claudio, Macelloni, Giovanni, Leduc-Leballeur, Marion, Favier, Vincent, Pohl, Benjamin, and Picard, Ghislain

Subjects
GRAIN size, ATMOSPHERIC rivers, ICE sheets, MICROWAVE radiometers, WIND speed
Abstract

This study explores the seasonal variations in snow grain size on the East Antarctic Plateau, where dry metamorphism occurs, by using microwave radiometer observations from 2000 to 2022. Local meteorological conditions and large-scale atmospheric phenomena have been considered in order to explain some peculiar changes in the snow grains. We find that the highest ice divide is the region with the largest grain size in the summer, mainly because the wind speed is low. Moreover, some extreme grain size values with respect to the average (over +3σ) were identified. In these cases, the ERA5 reanalysis revealed a high-pressure blocking close to the onsets of the summer increase in the grain size. It channels moisture intrusions from the mid-latitudes, through atmospheric rivers that cause major snowfall events over the plateau. If conditions of weak wind and low temperature occur during the following weeks, dry snow metamorphism is facilitated, leading to grain growth. This determines anomalous high maximums of the snow grain size at the end of summer. These phenomena confirm the importance of moisture intrusion events in East Antarctica and their impact on the physical properties of the ice sheet surface, with a co-occurrence of atmospheric rivers and seasonal changes in the grain size with a significance of over 95 %. [ABSTRACT FROM AUTHOR]

Published
2024
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9. Extremes of surface snow grains change in East Antarctica and their relationship with meteorological conditions

Author

Stefanini, Claudio, Macelloni, Giovanni, Leduc-Leballeur, Marion, Favier, Vincent, Pohl, Benjamin, and Picard, Ghislain

Abstract

This study explores the grain size seasonal variations on the East Antarctic Plateau, where dry metamorphism occurs, by using microwave radiometer observations from 2000 to 2022. Local meteorological conditions and large scale atmospheric phenomena have been considered in order to explain some peculiar changes of the snow grains. We find that the highest ice divide is the region with the largest grain size in the summer, mainly because the wind speed is low. Moreover, some extreme grain size values with respect to the average (over +3σ) were identified. In these cases, the ERA5 reanalysis revealed a high pressure blocking/ridge situation in the proximity of the onsets of the summer increase of the grain size, conveying the relatively warm and moist air coming from the mid latitudes, often associated with atmospheric rivers. If weak wind and low temperature conditions occur during the following weeks, dry snow metamorphism is facilitated, leading to grain growth. This determines anomalous high maximums of the snow grain size at the end of summer. These phenomena confirm the importance of moisture intrusion events in the East Antarctica and their impact on the physical properties of the ice sheet surface, with a co-occurrence of atmospheric rivers and seasonal changes of the grain size significant over 95 %.

Published
2023

10. Advanced melt indicators from passive microwave satellite observations in Antarctica

Author

Leduc-Leballeur, Marion, Picard, Ghislain, and Macelloni, Giovanni

Abstract

Liquid water has a significant impact on the microwave emissivity of the surface and, since decade, passive microwave observations are using to detect melt over ice sheet. However, the produced indicators are usually based on a single frequency and have different sensibilities. In the framework of the ESA 4D-Antarctica project, we propose to combine the binary melt indicators from the single-frequency to provide enhanced insights of the melt process. We focus on the 36 GHz and 19 GHz observations from the Advanced Microwave Scanning Radiometer 2 (AMSR2) satellite and the 1.4 GHz observations from the Soil Moisture and Ocean Salinity (SMOS) satellite. A deep theoretical analysis has been performed to explore the sensitivity of these frequencies to wet snow. In particular, 36 GHz distinguishes different stage of close surface melting and 1.4 GHz identifies the most intense period of melt during the summer. Moreover, AMSR2 provides observations in the afternoon (ascending pass) and in the night (descending pass) to detect the possible presence of a refrozen surface layer. The final classification is composed of nine melt status, which allows determining if a melt event was limited to the surface or if it was intense enough to inject significant water amounts at depths, and if refreezing happens during the night. This new product provides a clear and synthetic description of the melt status along the season. This opens a good opportunity for a potential use for the Copernicus Imaging Microwave Radiometer (CIMR) perspective., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Published
2023

11. On the retrieval of ice sheet temperature by using SMOS observations

Author

Leduc-Leballeur, Marion, Ritz, Catherine, Macelloni, Giovanni, and Picard, Ghislain

Abstract

The internal temperature is a key parameter for the ice sheet dynamics. Up to now temperature profile was available in few boreholes or from glaciological models. Macelloni et al. (2019) performed the first retrieval of the ice sheet temperature in Antarctica by using the European Space Agency (ESA)’s Soil Moisture and Ocean Salinity (SMOS) L-band observations. This is made possible due to the very low absorption of ice and the low scattering by particles (grain size, bubbles in ice) at L-band frequency, which implies a large penetration in the dry snow and ice of several hundreds of meters.Here, we present new estimates of the ice temperature profiles over Antarctica obtained from an improved algorithm. The minimization is based on Bayesian inference, which takes as free parameters: surface ice temperature, snow accumulation and geothermal heat flux. The parameter space investigation is achieved through a Markov Chain Monte Carlo (MCMC) method. A three-dimensional glaciological model (GRISLI, Quiquet et al., 2018) was used to train an emulator based on a deep neural network (DNN), which reproduces GRISLI temperature field for present time. This emulator generates temperature profiles as inputs for the Bayesian approach. The results show that the temperature profile can be estimated in a large part of Antarctica ice sheet, thanks to the comprehensive physics in the GRISLI model. The accuracy is typically < 2 K up to 2000 m in depth and ~5 K at 3200 m at Dome C., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Published
2023

12. Ice Sheet and Sea Ice Ultrawideband Microwave radiometric Airborne eXperiment (ISSIUMAX) in Antarctica: first results from Terra Nova Bay

Author

Brogioni, Marco, primary, Andrews, Mark J., additional, Urbini, Stefano, additional, Jezek, Kenneth C., additional, Johnson, Joel T., additional, Leduc-Leballeur, Marion, additional, Macelloni, Giovanni, additional, Ackley, Stephen F., additional, Bringer, Alexandra, additional, Brucker, Ludovic, additional, Demir, Oguz, additional, Fontanelli, Giacomo, additional, Yardim, Caglar, additional, Kaleschke, Lars, additional, Montomoli, Francesco, additional, Tsang, Leung, additional, Becagli, Silvia, additional, and Frezzotti, Massimo, additional

Published
2023
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13. Supplementary material to "Antarctic ice sheet paleo-constraint database"

Author

Lecavalier, Benoit S., primary, Tarasov, Lev, additional, Balco, Greg, additional, Spector, Perry, additional, Hillenbrand, Claus-Dieter, additional, Buizert, Christo, additional, Ritz, Catherine, additional, Leduc-Leballeur, Marion, additional, Mulvaney, Robert, additional, Whitehouse, Pippa L., additional, Bentley, Michael J., additional, and Bamber, Jonathan, additional

Published
2022
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14. Antarctic ice sheet paleo-constraint database

Author

Lecavalier, Benoit S., primary, Tarasov, Lev, additional, Balco, Greg, additional, Spector, Perry, additional, Hillenbrand, Claus-Dieter, additional, Buizert, Christo, additional, Ritz, Catherine, additional, Leduc-Leballeur, Marion, additional, Mulvaney, Robert, additional, Whitehouse, Pippa L., additional, Bentley, Michael J., additional, and Bamber, Jonathan, additional

Published
2022
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17. Airborne SnowSAR data at X and Ku bands over boreal forest, alpine and tundra snow cover

Author

Lemmetyinen, Juha, primary, Cohen, Juval, additional, Kontu, Anna, additional, Vehviläinen, Juho, additional, Hannula, Henna-Reetta, additional, Merkouriadi, Ioanna, additional, Scheiblauer, Stefan, additional, Rott, Helmut, additional, Nagler, Thomas, additional, Ripper, Elisabeth, additional, Elder, Kelly, additional, Marshall, Hans-Peter, additional, Fromm, Reinhard, additional, Adams, Marc, additional, Derksen, Chris, additional, King, Joshua, additional, Meta, Adriano, additional, Coccia, Alex, additional, Rutter, Nick, additional, Sandells, Melody, additional, Macelloni, Giovanni, additional, Santi, Emanuele, additional, Leduc-Leballeur, Marion, additional, Essery, Richard, additional, Menard, Cecile, additional, and Kern, Michael, additional

Published
2022
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20. CryoRad: a mission concept based on Low Frequency Wideband Radiometry for Remote Sensing of the Cryosphere

Author

Macelloni, Giovanni, Brogioni, Marco, Jezek, Kenneth, Leduc-Leballeur, Marion, Kaleschke, Lars, Picard, Ghislain, Ritz, Catherine, Nicholls, Keith, Boutin, Jacqueline, Turiel, Antonio, Lhermitte, Stef L., Mialon, Arnaud, Bertino, Laurent, Tietsche, Steffen, Closa, Josep, Macelloni, Giovanni, Brogioni, Marco, Jezek, Kenneth, Leduc-Leballeur, Marion, Kaleschke, Lars, Picard, Ghislain, Ritz, Catherine, Nicholls, Keith, Boutin, Jacqueline, Turiel, Antonio, Lhermitte, Stef L., Mialon, Arnaud, Bertino, Laurent, Tietsche, Steffen, and Closa, Josep

Abstract

Microwave sensors, both active and passive, are particularly suitable for observing polar regions because of their insensitivity to solar illumination and cloud coverage. However, most microwave sensors are sensitive to surface or near-surface properties because of their frequency of operation. Beginning in 2009, measurements of L-band radiometers (ESA SMOS, NASA Aquarius and SMAP) have provided the possibility of deriving deeper internal properties of ice sheets and sea ice as a result of the improved penetration capability at 1.4 GHz. It is estimated that such sensors are sensitive to about 30-40 cm for first year sea ice and to the upper 500-750 m of ice sheets, allowing the estimation of sea ice thickness (SMOS Sea Ice Thickness product, 2021) and ice sheet internal temperature profiles (Macelloni et al., 2019). The development of improved techniques for mitigating radio frequency interference in L-band radiometric missions has further led to the idea of using lower frequencies for monitoring the polar regions. A first airborne prototype (the Ultra-WideBand software defined RADiometer -UWBRAD) was developed in the US under a NASA -ESTO project led by The Ohio State University to observe brightness temperature spectra in the range 0.5-2 GHz (Andrews et al., 2017). Successful airborne campaigns in Greenland and Antarctica demonstrated the potential of this technique for inferring information on sea ice and internal ice sheets (Andrews et al., 2017, Yardim et al., 2020, Jezek et al 2018). Based on these promising results and the capabilities of the space industry, the CryoRad mission was proposed to ESA’s EE11 call. CryoRad consists of a single satellite hosting a single payload: a wideband, low-frequency microwave radiometer that explores the frequency range 0.4 GHz - 2 GHz with continuous frequency sampling, specifically designed to address scientific challenges in polar regions. The capability of CryoRad’s low frequencies to explore greater depths in ice sheets

Published
2022

21. Ice Sheet and Sea Ice Ultrawideband Microwave Airborne eXperiment (ISSIUMAX) in Antarctica: first results from Terra Nova Bay

Author

Brogioni, Marco, primary, Andrews, Mark J., additional, Urbini, Stefano, additional, Jezek, Kenneth C., additional, Johnson, Joel T., additional, Leduc-Leballeur, Marion, additional, Macelloni, Giovanni, additional, Ackley, Stephen F., additional, Bringer, Alexandra, additional, Brucker, Ludovic, additional, Demir, Oguz, additional, Fontanelli, Giacomo, additional, Yardim, Caglar, additional, Kaleschke, Lars, additional, Montomoli, Francesco, additional, Tsang, Leung, additional, Becagli, Silvia, additional, and Frezzotti, Massimo, additional

Published
2022
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22. 4D Antarctica

Author

Gourmelen, Noel, Malczyk, George, Wearing, Martin, Goldberg, Daniel, Ewart, Martin, Leduc-Leballeur, Marion, Macelloni, Giovanni, Wessel, Birgit, Werder, Mauro, Wuite, Jan, Nagler, Thomas, Shepherd, Andrew, Barletta, Valentina, Forsberg, Rene, Corr, Diamuid, Leeson, Amber, McMillian, Malcom, Rigby, Richard, Hogg, Anna E., Ritz, Catherine, and Picard, Ghislain

Subjects
subglacial, supra-glacial, Earth Observation missions, hydrology, ice-sheet, Anarctica
Published
2022

24. Exploiting the ANN Potential in Estimating Snow Depth and Snow Water Equivalent From the Airborne SnowSAR Data at X- and Ku-Bands

Author

Santi, Emanuele, primary, Brogioni, Marco, additional, Leduc-Leballeur, Marion, additional, Macelloni, Giovanni, additional, Montomoli, Francesco, additional, Pampaloni, Paolo, additional, Lemmetyinen, Juha, additional, Cohen, Juval, additional, Rott, Helmut, additional, Nagler, Thomas, additional, Derksen, Chris, additional, King, Joshua, additional, Rutter, Nick, additional, Essery, Richard, additional, Menard, Cecile, additional, Sandells, Melody, additional, and Kern, Michael, additional

Published
2022
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26. Antarctic ice sheet paleo-constraint database.

Author

Lecavalier, Benoit S., Tarasov, Lev, Balco, Greg, Spector, Perry, Hillenbrand, Claus-Dieter, Buizert, Christo, Ritz, Catherine, Leduc-Leballeur, Marion, Mulvaney, Robert, Whitehouse, Pippa L., Bentley, Michael J., and Bamber, Jonathan

Subjects
ANTARCTIC ice, ICE sheets, ICE, BEDROCK, GEOMETRIC surfaces
Abstract

We present a database of observational constraints on past Antarctic ice sheet changes during the last glacial cycle intended to consolidate the observations that represent our understanding of past Antarctic changes, for state-space estimation, and paleo-model calibrations. The database is a major expansion of the initial work of Briggs and Tarasov (2013). It includes new data types and multi-tier data quality assessment. The updated constraint database "AntICE2" consists of observations of past grounded and floating ice sheet extent, past ice thickness, past relative sea level, borehole temperature profiles, and present-day bedrock displacement rates. In addition to paleo-observations, the present-day ice sheet geometry and surface ice velocities are incorporated to constrain the present-day ice sheet configuration. The method by which the data is curated using explicitly defined criteria is detailed. Moreover, the observational uncertainties are specified. The methodology by which the constraint database can be applied to evaluate a given ice sheet reconstruction is discussed. The implementation of the "AntICE2" database for Antarctic ice sheet model calibrations will improve Antarctic ice sheet predictions during past warm and cold periods and yield more robust paleo model spin ups for forecasting future ice sheet changes. [ABSTRACT FROM AUTHOR]

Published
2022
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27. Airborne SnowSAR data at X- and Ku- bands over boreal forest, alpine and tundra snow cover

Author

Lemmetyinen, Juha, primary, Cohen, Juval, additional, Kontu, Anna, additional, Vehviläinen, Juho, additional, Hannula, Henna-Reetta, additional, Merkouriadi, Ioanna, additional, Scheiblauer, Stefan, additional, Rott, Helmut, additional, Nagler, Thomas, additional, Ripper, Elisabeth, additional, Elder, Kelly, additional, Marshall, Hans-Peter, additional, Fromm, Reinhard, additional, Adams, Marc, additional, Derksen, Chris, additional, King, Joshua, additional, Meta, Adriano, additional, Coccia, Alex, additional, Rutter, Nick, additional, Sandells, Melody, additional, Macelloni, Giovanni, additional, Santi, Emanuele, additional, Leduc-Leballeur, Marion, additional, Essery, Richard, additional, Menard, Cecile, additional, and Kern, Michael, additional

Published
2021
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29. Estimating surface melt in Antarctica from 1979 to 2022, using a statistically parameterized positive degree-day model.

Author

Yaowen Zheng, Golledge, Nicholas R., Gossart, Alexandra, Picard, Ghislain, and Leduc-Leballeur, Marion

Abstract

Surface melt is one of the primary drivers of ice shelf collapse in Antarctica. Surface melting is expected to increase in the future as the global climate continues to warm, because there is a statistically significant positive relationship between air temperature and melt. Enhanced surface melt will negatively impact the mass balance of the Antarctic Ice Sheet (AIS) and, through dynamic feedbacks, induce changes in global mean sea level (GMSL). However, current understanding of surface melt in Antarctica remains limited in past, present or future contexts. Continental-scale spaceborne observations of surface melt are limited to the satellite era (1979-present), meaning that current estimates of Antarctic surface melt are typically derived from surface energy balance (SEB) or positive degree-day (PDD) models. SEB models require diverse and detailed input data that are not always available and require considerable computational resources. The PDD model, by comparison, has fewer input and computational requirements and is therefor suited for exploring surface melt scenarios in the past and future. The use of PDD schemes for Antarctic melt has been less extensively explored than their application to surface melting of the Greenland Ice Sheet, particularly in terms of a spatially-varying parameterization. Here, we construct a PDD model, force it only with 2-m air temperature reanalysis data, and parameterize it by minimizing the error with respect to satellite observations and SEB model outputs over the period 1979 to 2022. We compare the spatial and temporal variability of surface melt from our PDD model over the last 43 years with that of satellite observations and SEB simulations. We find that the PDD model can generally capture the same spatial and temporal surface melt patterns. Although there were at most four years over/under-estimation on ice shelf regions in the epoch, these discrepancies reduce when considering the whole AIS. With the limitations discussed, we suggest that an appropriately parameterized PDD model can be a valuable tool for exploring Antarctic surface melt beyond the satellite era. [ABSTRACT FROM AUTHOR]

Published
2022
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33. ICE SHEET AND SEA ICE ULTRAWIDEBAND MICROWAVE RADIOMETRIC AIRBORNE EXPERIMENT (ISSIUMAX) IN ANTARCTICA: FIRST RESULTS FROM TERRA NOVA BAY.

Author

Brogioni, Marco, Andrews, Mark J., Urbini, Stefano, Jezek, Kenneth C., Johnson, Joel T., Leduc-Leballeur, Marion, Macelloni, Giovanni, Ackley, Stephen F., Bringer, Alexandra, Brucker, Ludovic, Demir, Oguz, Fontanelli, Giacomo, Yardim, Caglar, Kaleschke, Lars, Montomoli, Francesco, Leung Tsang, Becagli, Silvia, and Frezzotti, Massimo

Abstract

An airborne microwave wide-band radiometer (500-2000 MHz) was operated for the first time in Antarctica to better understand the emission properties of sea ice, outlet glaciers and the interior ice sheet from Terra Nova Bay to Dome C. The different glaciological regimes were revealed to exhibit unique spectral signatures in this portion of the microwave spectrum. Generally, the brightness temperatures over the inland ice sheet were warmest at the lowest frequencies consistent with models that predict that those channels sensed the deeper, warmer parts of the ice sheet. Spectra along the lengths of outlet glaciers were modulated by the deposition and erosion of snow, driven by strong katabatic winds. Similar to previous experiments in Greenland, the brightness temperatures across the frequency band were low in crevasse areas. Variations in brightness temperature were consistent with spatial changes in sea ice type identified in satellite imagery and in situ ground penetrating radar data. The results contribute to a better understanding of the utility of microwave wide-band radiometry for cryospheric studies and also advance knowledge of the important physics underlying existing L-band radiometers operating in space. [ABSTRACT FROM AUTHOR]

Published
2022
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35. Modelling the L-Band Snow-Covered Surface Emission in a Winter Canadian Prairie Environment

Author

Roy, Alexandre, Leduc-Leballeur, Marion, Picard, Ghislain, Royer, Alain, Toose, Peter, Derksen, Chris, Lemmetyinen, Juha, Berg, Aaron, Rowlandson, Tracy, Schwank, Mike, Centre d'Applications et de Recherches en TELédétection [Sherbrooke] (CARTEL), Département de géomatique appliquée [Sherbrooke] (UdeS), Université de Sherbrooke (UdeS)-Université de Sherbrooke (UdeS), Departement des sciences de l’environnement [Trois-Rivieres], Université du Québec à Trois-Rivières (UQTR), Centre d'Etudes Nordiques (CEN), Université Laval [Québec] (ULaval), Institute of Applied Physics 'Nello Carrara' (IFAC), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Climate Research Division [Toronto], Environment and Climate Change Canada, Finnish Meteorological Institute (FMI), University of Guelph, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, and Gamma Remote Sensing Research and Consulting AG

Subjects
Frozen soil, Science, [SDE]Environmental Sciences, L-band emission, snow, WALOMIS, ground-based radiometer
Abstract

International audience; Detailed angular ground-based L-band brightness temperature (TB) measurements over snow covered frozen soil in a prairie environment were used to parameterize and evaluate an electromagnetic model, the Wave Approach for LOw-frequency MIcrowave emission in Snow (WALOMIS), for seasonal snow. WALOMIS, initially developed for Antarctic applications, was extended with a soil interface model. A Gaussian noise on snow layer thickness was implemented to account for natural variability and thus improve the TB simulations compared to observations. The model performance was compared with two radiative transfer models, the Dense Media Radiative Transfer-Multi Layer incoherent model (DMRT-ML) and a version of the Microwave Emission Model for Layered Snowpacks (MEMLS) adapted specifically for use at L-band in the original one-layer configuration (LS-MEMLS-1L). Angular radiometer measurements (30°, 40°, 50°, and 60°) were acquired at six snow pits. The root-mean-square error (RMSE) between simulated and measured TB at vertical and horizontal polarizations were similar for the three models, with overall RMSE between 7.2 and 10.5 K. However, WALOMIS and DMRT-ML were able to better reproduce the observed TB at higher incidence angles (50° and 60°) and at horizontal polarization. The similar results obtained between WALOMIS and DMRT-ML suggests that the interference phenomena are weak in the case of shallow seasonal snow despite the presence of visible layers with thicknesses smaller than the wavelength, and the radiative transfer model can thus be used to compute L-band brightness temperature.

Published
2018
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38. Remote Sensing of Sea Ice Thickness and Salinity With 0.5–2 GHz Microwave Radiometry

Author

Jezek, Kenneth C., primary, Kwok, Ronald, additional, Kaleschke, Lars, additional, Belgiovane, Domenic J., additional, Chen, Chi-Chih, additional, Bringer, Alexandra, additional, Johnson, Joel T., additional, Demir, Oguz, additional, Andrews, Mark J., additional, Macelloni, Giovanni, additional, Brogioni, Marco, additional, Leduc-Leballeur, Marion, additional, Tan, Shurun, additional, and Tsang, Leung, additional

Published
2019
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44. Oceanic influence of the Gulf of Guinea on the West African monsoon

Author

Leduc-Leballeur, Marion, Leduc-Leballeur, Marion, ESTER - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris VI, and Laurence EYMARD et Gaëlle DE COËTLOGON

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Statistical analyses, Interactions air-mer, West African monsoon, Mousson africaine, Variabilité intrasaisonnière, Air-sea interactions, Tropical Atlantic, AMMA, Intraseasonal variability, Analyses statistiques, Atlantique tropical, [PHYS.PHYS.PHYS-AO-PH] Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]
Abstract

The West African monsoon is a complex interaction between the ocean, the land-surface and the atmosphere. Many studies showed a link between the seasonal cooling of the ocean in the Gulf of Guinea (equatorial upwelling) and the monsoon. The aim of this thesis is to explore the air-sea interaction mechanisms, which act on the coastal precipitation of the monsoon during boreal spring. The study is based on in situ and satellite measurements as well as reanalysis datasets. The 2006 monsoon season is analysed thanks to the vast set of observations collected by the AMMA (African Monsoon Multidisciplinary Analyses) project during this year. This study has led to a description of the marine atmospheric boundary layer in the eastern equatorial Atlantic. Results show that the sea surface temperature (SST) front on the northern boundary of the equatorial upwelling is a key zone for air-sea interactions in this region. Thus, a SST cooling south of the equator is generated by a southeasterly wind burst and intensifies the SST front. Consequently, the surface wind tends to weak above cold SST and to strengthen above warm SST. Then, the effect of southeasterly wind bursts in the Gulf of Guinea on the coastal precipitation is studied with satellite measurements and reanalysis datasets on the 2000-2009 period. Results show that a succession of SST coolings is generated by a succession of southeasterly wind bursts in the eastern equatorial Atlantic. These coolings act on the surface wind and the atmospheric circulation between the front and the Guinean coast and favour convection along the coast. This confirms the key role of the SST front and highlights its influence on the coastal precipitation. Finally, these intraseasonal events seem to play an important role in the seasonal evolution of the precipitation before the onset of the West African monsoon., La mousson africaine est un phénomène complexe issu du couplage entre le continent, l'océan et l'atmosphère. De nombreuses études ont montré un lien entre le refroidissement saisonnier de l'océan dans le golfe de Guinée (upwelling équatorial) et la mousson. Cette thèse vise à explorer les mécanismes d'interactions océan-atmosphère agissant sur les précipitations côtières de la mousson africaine au printemps boreal. Ce travail s'appuie à la fois sur des mesures in situ et satellites, et sur des données de réanalyses. La saison de mousson de 2006 a été analysée grâce au grand nombre de données rassemblées cette année-là par le programme AMMA (Analyse Multidisciplinaire de la Mousson Africaine). Cette étude a permis de décrire la couche limite atmosphérique marine dans l'Est de l'Atlantique équatorial. Il en résulte que le front de température de surface de l'océan (SST) établi au nord de l'upwelling équatorial est une zone clé des interactions océan-atmosphère dans cette région. Ainsi, il a été observé qu'un refroidissement de quelques jours de la SST au sud de l'équateur est engendré par un coup de vent des alizés de sud-est et a pour effet d'intensifier le front de SST. Le vent de surface a alors tendance à ralentir au-dessus des SST froides et accélérer au-dessus des SST chaudes. L'effet des coups de vent dans le golfe de Guinée sur les précipitations côtières a ensuite été étudié à partir de mesures satellites et de réanalyses sur la période 2000-2009. Il apparaît qu'une succession de coup de vent entraîne une succession de refroidissement dans la zone d'upwelling équatorial. Ces refroidissements intensifient le front de SST qui agit sur le vent de surface et la circulation atmosphérique avec pour effet de favoriser la convection à la côte. Ces résultats confirment donc le rôle essentiel du front de SST et confortent l'hypothèse de son influence sur les précipitations côtières. Enfin, ces événements intrasaisonniers semblent influencer l'évolution saisonnière des précipitations durant la période qui précède le déclenchement de la mousson africaine.

Published
2012

46. Atmospheric response to sea-surface temperature in the eastern equatorial Atlantic at quasi-biweekly time-scales

Author

de Coëtlogon, Gaëlle, Leduc-Leballeur, Marion, Meynadier, Remi, Bastin, Sophie, Diakhaté, Moussa, Eymard, Laurence, Giordani, Hervé, Janicot, Serge, Lazar, Alban, ESTER - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), SPACE - LATMOS, Laboratoire de Physique de l'Atmosphère et de l'Océan Siméon Fongang (LPAO-SF), École Supérieure Polytechnique de Dakar (ESP), Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD)-Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD), Processus de la variabilité climatique tropicale et impacts (PARVATI), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), 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)), 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), Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD), 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 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), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-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)), 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)), 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), and 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)

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], intraseasonal variability, quasi-biweekly oscillation, Physics::Space Physics, air-sea interaction, Atlantic, Astrophysics::Solar and Stellar Astrophysics, Atlantic cold tongue, SST front, eastern tropical Atlantic, eastern tropical, Physics::Atmospheric and Oceanic Physics
Abstract

The surface-wind response to sea-surface temperature (SST) and SST meridional gradient is investigated in the Gulf of Guinea by using daily observations and re-analyses in the 2000-2009 decade, with a focus on boreal spring and summer months (May to August), where quasi-biweekly fluctuations in the position of the northern front of the equatorial cold tongue induce quasi-biweekly equatorial SST anomalies. Following a large-scale wind acceleration (deceleration), an equatorial SST cold (warm) anomaly is created within a few days. In order to explain the local atmospheric response to this SST anomaly, the two following mechanisms are invoked: first, a colder (warmer) ocean decreases (increases) the vertical stability in the marine atmospheric boundary layer, which favours a weaker (stronger) surface wind; and second, a negative (positive) anomaly of SST meridional gradient induces a positive (negative) anomaly of the sea-level-pressure meridional gradient, which decelerates (accelerates) the surface wind. The first mechanism has an immediate effect in the equatorial belt between 1 degrees S and 1 degrees N (and to a lesser extent between 3 degrees S and 1 degrees S), whereas the second takes 1 or 2 days to adjust and damps anomalous southeasterlies up to 800 hPa in the low troposphere between 7 degrees S and 1 degrees N, through reversed anomalies of meridional SST and pressure gradient. This negative feedback leads to weaker (stronger) winds in the southeastern tropical Atlantic, which forces the opposite phase of the oscillation within about 1 week. Around the Equator, where the amplitude of the oscillation is found to be maximal, both mechanisms combine to maximize the wind response to the front fluctuations. Between the Equator and the coast, a low-level secondary atmospheric circulation takes control of the surface-wind acceleration or deceleration around 3 degrees N, which reduces the influence of the SST-front fluctuations.

Published
2014
Full Text
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47. Air-sea interaction in the eastern Equatorial Atlantic at intraseasonal timescales in boreal spring and summer: a quasi-biweekly equatorial oscillation

Author

De Coëtlogon, Gaëlle, Leduc-Leballeur, Marion, Meynadier, Remi, Bastin, Sophie, Diakhaté, Moussa, Eymard, Laurence, Giordani, Hervé, Janicot, Serge, Lazar, Alban, ESTER - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), SPACE - LATMOS, 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), Institut Pierre-Simon-Laplace (IPSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-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)-Centre National de la Recherche Scientifique (CNRS), 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), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-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), École normale supérieure - Paris (ENS Paris)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National d'Études Spatiales [Toulouse] (CNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-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)), École normale supérieure - Paris (ENS Paris), and 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)

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

A quasi-biweekly oscillation in the northern front of the eastern equatorial Atlantic's cold tongue is investigated by using observations and reanalyses in the 2000-2009 decade, with a focus on boreal spring and summer months (May to August). Fluctuations of the front latitude induce quasi-biweekly equatorial sea surface temperature (SST) anomalies that are strongly coupled with surface wind anomalies. Linear regressions performed onto a Northern Cold Tongue Index emphasize the two following mechanisms to explain the atmospheric adjustment to SST anomalies: first, a colder (warmer) ocean decreases (increases) the vertical mixing in the marine atmospheric boundary layer, which favors a weaker (stronger) surface wind; and second, a positive (negative) anomaly of SST meridional gradient induces a negative (positive) anomaly in sea level pressure meridional gradient, which accelerate (decelerate) the surface wind. The first mechanism has an immediate effect, while the second takes one or two days to adjust. Following a large-scale wind acceleration (deceleration), the second mechanism weakens (strengthens) southeasterlies in the low troposphere south of 1°N, through reversed SST and meridional pressure gradient anomalies, thereby forcing the opposite phase of the oscillation within about 6 to 8 days. Between the equator and the coast, both mechanisms possibly explain the observed intensification of the recirculation loop between the equator and the Guinean coast in the low troposphere, which sustains and accelerates surface wind around 3°N.

Published
2013

48. Air-sea interaction in the Gulf of Guinea at intraseasonal timescales: wind bursts and coastal precipitation in boreal spring

Author

Leduc-Leballeur, Marion, de Coëtlogon, Gaëlle, Eymard, Laurence, 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), ESTER - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-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 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), and AMMA

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], West African monsoon, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, [SDE.MCG]Environmental Sciences/Global Changes, Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, Tropical Atlantic, [SDU.STU.ME]Sciences of the Universe [physics]/Earth Sciences/Meteorology, Physics::Atmospheric and Oceanic Physics, Physics::Geophysics
Abstract

International audience; The role of air-sea interaction in the boreal spring precipitation of the West African monsoon is explored through the wind variability in the Gulf of Guinea. Linear regressions are performed in May-June during the decade 2000-2009 to investigate the origin and effect of the surface wind strengthening north of the Equator. It appears that the equatorial sea-surface temperature cooling intensifies a surface-wind equatorial divergence/coastal convergence circulation, and generates a cross-equatorial pressure gradient, which both strengthen the southerlies north of the Equator. This increases subsidence above the ocean and convection in the northern Gulf of Guinea. In addition, an abrupt change is observed in the surface wind pattern in the eastern equatorial Atlantic (EEA) between April and July. To investigate the transition mechanisms, a reference date is defined as the date when the surface wind north of the Equator becomes and remains stronger than south of the Equator. Thus the maintenance of strong southerlies north of the Equator is linked to a coincident installation of a deep circulation on the whole troposphere and a northward shift of the low atmospheric local circulation. The resulting sharp seasonal transition coincides each year with a southeasterly wind burst, suggesting that the equatorial SST cooling plays a role in the precipitation along the African coast during boreal spring

Published
2012
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49. Impact of the air-sea coupling in the Gulf of Guinea on the Guinean coastal water cycle in boreal spring

Author

Meynadier, Remi, de Coëtlogon, Gaëlle, Eymard, Laurence, Leduc-Leballeur, Marion, Bastin, Sophie, Janicot, Serge, Bock, Olivier, Flamant, Cyrille, SPACE - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), ESTER - LATMOS, 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), LAboratoire de REcherche en Géodésie [Paris] (LAREG), Laboratoire des Sciences et Technologies de l'Information Géographique (LaSTIG), École nationale des sciences géographiques (ENSG), Institut National de l'Information Géographique et Forestière [IGN] (IGN)-Institut National de l'Information Géographique et Forestière [IGN] (IGN)-École nationale des sciences géographiques (ENSG), Institut National de l'Information Géographique et Forestière [IGN] (IGN)-Institut National de l'Information Géographique et Forestière [IGN] (IGN), 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), and 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)

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, [SDE.MCG]Environmental Sciences/Global Changes
Published
2012

50. Air-sea interaction in the Gulf of Guinea at intraseasonal timescales : A quasi-biweekly oscillation in the eastern equatorial Atlantic

Author

de Coëtlogon, Gaëlle, Leduc-Leballeur, Marion, Meynadier, Remi, Bastin, Sophie, Eymard, Laurence, Janicot, Serge, Lazar, Alban, Diakhaté, Moussa, ESTER - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), SPACE - LATMOS, Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), 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), 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), and 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)

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, [SDE.MCG]Environmental Sciences/Global Changes
Published
2012

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