Marion Leduc‐Leballeur

Nello Carrara Institute of Applied Physics

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Giovanni Macelloni

Nello Carrara Institute of Applied Physics

Ghislain Picard

Institut des Géosciences de l'Environnement

Marco Brogioni

Nello Carrara Institute of Applied Physics

Joel T. Johnson

The Ohio State University

Kenneth C. Jezek

The Ohio State University

Laurence Eymard

Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques

Gaëlle de Coëtlogon

Laboratoire atmosphères, milieux, observations spatiales

Mark Andrews

The Ohio State University

Catherine Ritz

Centre National de la Recherche Scientifique

Francesco Montomoli

Imperial College London

Cooperative Institutions

Centre National de la Recherche Scientifique

Institut de Recherche pour le Développement

Sorbonne Université

Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques

Université de Toulouse

Institut Pierre-Simon Laplace

Université Toulouse III - Paul Sabatier

Laboratoire atmosphères, milieux, observations spatiales

The Ohio State University

Laboratoire d’Études en Géophysique et Océanographie Spatiales

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Carols Campaign, Scientific Data Analysis Results

IGARSS 2022 - 2022 IEEE International Geoscience and Remote Sensing Symposium (2008)

Mickaël Pardé Mehrez Zribi Pascal Fanise P. Leroy Danièle Hauser

The CAROLS L-band radiometer, which is built and designed as a copy of DTU EMIRAD II instrument will be used in conjunction with other airborne instruments (in particular the C-Band scatterometer STORM) in coordination with in situ field campaigns for futur SMOS CAL/VAL activities. A validation campaign with four flights was made over the South West of France and the Bay of Biscay (Atlantic Ocean) in September 2007. Different instrumented sites were over ocean and land surfaces were coverecd. Moreover, in order to qualify the radiometric data, different types of aircraft maneuvers were performed over ocean: circle flights, wing and nose wags. We present in this paper the first analysis of the data quality using these ocean measurements. We show a very good sensitivity of both channels.

Scatterometer

10.1109/igarss.2008.4779217

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Citations (1)

Comment on tc-2023-61

Claudio Stefanini Giovanni Macelloni Marion Leduc‐Leballeur Vincent Favier Benjamin Pohl

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 %.

10.5194/tc-2023-61-rc2

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Comment on tc-2022-85

Ghislain Picard Marion Leduc‐Leballeur Alison F. Banwell Ludovic Brucker Giovanni Macelloni

Surface melting on the Antarctic Ice Sheet has been monitored by satellite microwave radiometery for over 40 years. Despite this long perspective, our understanding of the microwave emission from wet snow is still limited, preventing the full exploitation of these observations to study supraglacial hydrology. Using the Snow Microwave Radiative Transfer (SMRT) model, this study investigates the sensitivity of microwave brightness temperature to snow liquid water content at frequencies from 1.4 to 37 GHz. We first determine the snowpack properties for 8 selected coastal sites by retrieving profiles of density, grain size and ice layers from microwave observations when the snowpack is dry during winter time. Second, a series of brightness temperature simulations is run with added water. The results show that: i) a small amount of liquid water (≈0.5 kg m-2 can be detected, but the actual amount can not be retrieved in the full range of possible water contents, ii) the detection of a buried wet layer is possible up to a maximum 1 to 6 m depth depending on the frequency (6–37 GHz) and on the site, iii) surface ponds and water-saturated areas may prevent melt detection, but the current coverage of these water bodies in the large satellite field of view is presently too small in Antarctica to have noticeable effects, iv) at 1.4 GHz, while the simulations are less reliable, we found a weaker sensitivity to liquid water and the maximal depth of detection is relatively shallow (<10 m) compared to the typical radiation penetration depth in dry firn (≈1000 m) at this low frequency. These numerical results pave the way for the development of improved multi-frequency algorithms to detect melt intensity and depth in the Antarctic snowpack.

Snowpack

Liquid water content

10.5194/tc-2022-85-rc1

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

Quarterly Journal of the Royal Meteorological Society (2013)

Gaëlle de Coëtlogon Marion Leduc‐Leballeur Rémi Meynadier Sophie Bastin Moussa Diakhaté

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°S and 1°N (and to a lesser extent between 3°S and 1°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°S and 1°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°N, which reduces the influence of the SST‐front fluctuations.

Anomaly (physics)

Surface pressure

Pressure gradient

Madden–Julian oscillation

10.1002/qj.2250

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Simulating 0.4–2.5 GHz Brightness Temperatures of the Ross Ice Shelf, Antarctica

IEEE Geoscience and Remote Sensing Letters (2024)

Marco Brogioni Kenneth C. Jezek Joel T. Johnson Marion Leduc‐Leballeur Caglar Yardim

Ice shelves are important parts of the cryosphere that influence ice sheet dynamics and mass loss. The internal temperatures of ice shelves are currently known only from a few borehole sites or from glaciological models. Microwave radiometry in the 0.4–2.5 GHz range is capable of receiving thermal emissions from deep within an ice shelf and thereby providing information on internal temperatures. This letter reports modeling studies of the brightness temperature of the Ross Ice Shelf (RIS) from 0.4 to 2.5 GHz that provide insight into the potential of microwave radiometers for measuring ice shelf internal properties.

Lead (geology)

Radiometry

10.1109/lgrs.2024.3368613

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Observation of the marine atmospheric boundary layer in the Gulf of Guinea during the 2006 boreal spring

Quarterly Journal of the Royal Meteorological Society (2011)

Marion Leduc‐Leballeur Laurence Eymard Gaëlle de Coëtlogon

Abstract In situ , satellite and model analyses data in April–July 2006 are used to investigate the links between sea surface temperature (SST) and the marine atmospheric boundary layer (MABL) in the Gulf of Guinea. The study region between 10°W and 6°E is divided into three areas with different characteristics: the North Area (4.5°N to 1°N) with the wettest atmosphere and the warmest SST, the Upwelling Area (1°N to 4°S) with the strongest SST decrease, and the South Area (4°S to 8°S) with a drier atmosphere and a more slowly decreasing SST than in the Upwelling Area. The key zone of the air‐sea interactions in this region seems to be the SST front between North and Upwelling Areas. On the one hand, the study of the MABL on either side of the front shows a well‐mixed layer between the surface and about 500 m high, sensitive to surface variations, which gets shallower (deeper) when the SST decreases (increases). The MABL height (about 1500 m) follows the same variations but is not exactly collocated with the SST variations. On the other hand, the observation of the MABL across the SST front shows a strengthening of southeasterlies in the South Area coinciding with a strong SST decrease in the Upwelling Area. In the latter, the wind weakens above the colder SST. Besides, in the North Area, the wind strengthens above the warmer SST. However, the wind acceleration spans from the equator to 2°N in April and as far as 4°N in June. A convergence zone is observed in the vicinity of 2°N in April, suggesting a convection activity there, favoured by the SST front. Copyright © 2011 Royal Meteorological Society

Mixed layer

10.1002/qj.808

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Citations (16)

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

Juha Lemmetyinen Juval Cohen Anna Kontu Juho Vehviläinen Henna-Reetta Hannula

Abstract. The European Space Agency SnowSAR instrument is a side looking, dual polarized (VV/VH), X/Ku band synthetic aperture radar (SAR), operable from a small aircraft. Between 2010 and 2013, the instrument was deployed at several sites in Northern Finland, Austrian Alps, and northern Canada. The purpose of the airborne campaigns was to measure the backscattering properties of snow-covered terrain to support the development of snow water equivalent retrieval techniques using SAR. SnowSAR was deployed in Sodankylä, Northern Finland for a single flight mission in March 2011 and twelve missions at two sites (tundra and boreal forest) in the winter of 2011–2012. Over the Austrian Alps, three flight missions were performed between November 2012 and February 2013 over three sites located in different elevation zones, representing a montane valley, Alpine tundra, and a glacier environment. In Canada, a total of two missions were flown in March and April 2013, over sites in the Trail Valley Creek watershed, Northwest Territories, representative of the tundra snow regime. This paper introduces the airborne SAR data, as well as coincident in situ information on land cover, vegetation and snow properties. To facilitate easy access to the data record the datasets described here are deposited in a permanent data repository (https://doi.pangaea.de/10.1594/PANGAEA.933255; Lemmetyinen et al., 2021). A temporary link to access the data without login information is provided for reviewers of this manuscript: https://www.pangaea.de/tok/e8c562c3c8a15ac34daa83d00c76fcb347330884.

Pangaea

Elevation (ballistics)

10.5194/essd-2021-239

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Citations (2)

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

Yaowen Zheng Nicholas R. Golledge Alexandra Gossart Ghislain Picard Marion Leduc‐Leballeur

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.

Greenland ice sheet

Antarctic ice sheet

10.5194/tc-2022-192

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Community Development of the Snow Microwave Radiative Transfer Model for Passive, Active and Altimetry Observations of the Cryosphere

Melody Sandells Ghislain Picard Henning Löwe Nina Maaß Mai Winstrup

The Snow Microwave Radiative Transfer (SMRT) model was initially developed to explore the sensitivity of microwave scattering to snow microstructure for active and passive remote sensing applications. Here, we discuss the modular design of SMRT that has enabled its rapid extension by the community. SMRT can now represent a layered medium consisting of snow, land ice, lake ice and/or sea ice overlying a substrate of soil, water or parameterized by reflectivity. A time-dependent radiative transfer solution method has also been added to allow for low resolution mode altimetry applications. We illustrate the use of SMRT to simulate brightness temperature for snow on lake ice, backscatter for snow on soil and altimeter waveforms for snow on sea ice.

Sea ice concentration

Scatterometer

Backscatter (email)

10.1109/igarss47720.2021.9553580

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Coupling Solid Earth and ice temperature models to estimate geothermal heat flow

Judith Freienstein Wolfgang Szwillus Marion Leduc‐Leballeur Giovanni Macelloni J. Ebbing

Geothermal heat flow (GHF) is a key element of Solid Earth-cryosphere interactions. However, polar regions as Antarctica are only sparsely covered with heat flow determinations from boreholes, so one must rely on interpolation or regression models of GHF (e.g. machine learning) from other sources to derive a regional map. Interpolation/regression of GHF in this manner depends strongly on the available sparse boreholes, which can distort the resulting regional map. Additional information can be gained from the SMOS (Soil Moisture and Ocean Salinity) satellite by inferring ice temperature profiles with a Bayesian inversion from remote sensing microwave radiometer data. This retrieval uses geothermal heat flow as a free parameter so that it provides a posterior distribution of the GHF needed to explain the ice temperature profiles. We aim to reconcile geophysical geothermal heat flow models with the ice temperature profiles and improve the estimates of GHF with this coupling. We use stationary thermal modelling where we force the ice temperature and lithospheric temperature model to converge at the base of the ice. Using stochastic inversion, we estimate the thermal parameters in the lithosphere. The posterior distribution of the retrieval as constraint for the GHF is included as prior distribution to the inversion to the stationary thermal modelling so that the GHF with the highest likelihood can be estimated. With our approach, we can evaluate a GHF distribution that both explains the ice temperature and lithospheric temperature models and covers large parts of Antarctica.

Heat flow

Geothermal heating

10.5194/egusphere-egu24-7654

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