8+ years of soil moisture and ocean salinity data over the globe from SMOS

Category : CATDS, L2, L3, Ocean

This animation was prepared by Dimitry Khvorostyanov from LOCEAN with SMOS data from CATDS (Soil moisture level 3 and Ocean salinity debiased V3)

Enjoy

Special Issue « New Outstanding Results over Land from the SMOS Mission »

Category : Data

from Amen Al-Yaari and Arnaud Mialon

Call for publications

Dear Colleagues,

Surface soil moisture (the water content in the first centimeters of soil) is an essential climate variable that plays an important role in land–atmosphere interactions. Soil moisture is widely used in improving climate model predictions/projections, weather forecasting, drought monitoring, rainfall estimations, etc.

Monitoring surface soil moisture at a global scale has recently become possible thanks to microwave remote sensing. SMOS (Soil Moisture and Ocean Salinity) was the first dedicated soil moisture mission that has been in orbit for eight years. The SMOS satellite was launched by the European Space Agency (ESA) in 2009, carrying on board a radiometer in the L-band frequency with a native spatial resolution of ~43 km. Since then, soil moisture and vegetation optical depth (VOD) have been retrieved from multi-angular brightness temperature observations relying mainly on a radiative transfer model.

This is a dedicated Special Issue on SMOS. We welcome studies on all subjects that are related to the SMOS satellite and its products.

Potential topics include, but are not limited to, the following:

  • the improvements in the soil moisture/VOD retrieval algorithms;
  • the evaluation/validation of the SMOS soil moisture and VOD products;
  • SMOS synergy with other remote sensing observations or models simulations;
  • SMOS soil moisture/VOD applications for agriculture, hydrology, etc.

Dr. Amen Al-Yaari
Dr. Arnaud Mialon
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Remote Sensing is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI’s English editing service prior to publication or during author revisions.

http://www.mdpi.com/journal/remotesensing/special_issues/smos_rs

SMOS: A new tool to monitor the carbon budget of vegetation: first application to the African continent

Category : L3

How do the vegetation carbon stocks change at the continental scale? What are the drivers of these changes? These are central questions for the sciences of Climate and for the application of international agreements on climate. A study coordinated by the University of Copenhagen1 has developed a new approach to investigate this issue. In collaboration with scientific teams2 from CEA, CNES and CNRS, INRA has coordinated the development of the new data set derived from SMOS microwave observations which is used to quantify vegetation carbon stocks. The study demonstrates that over the African continent and during the 2010-2016 period, the net carbon balance is negative (corresponding to a decrease of the quantity of carbon stored in the vegetation biomass) and that most of the carbon losses occurred in dryland savannahs. These results were published on 9th April 2018 in the journal Nature Ecology and Evolution.

Satellite passive microwaves reveal recent climate-induced carbon losses in African drylands, Martin Brandt, et al., Nature Ecology & Evolution, Apr 9, 2018, doi:10.1038/s41559-018-0530-6

Changes in aboveground vegetation carbon stocks in sub-Saharan Africa over 2010–2016. Regions with significant negative (carbon source) or positive (carbon sink) carbon changes are shown, respectively, in red or green.

© M. Brandt – Université de Copenhague

Scientists from INRA and their colleagues have produced a new data set of the vegetation index referred to as L-VOD (L-band vegetation optical depth), retrieved from space-borne observations of the SMOS satellite over 2010-2016. The data have been used to quantify annual aboveground biomass-carbon changes in sub-Saharan Africa stocks over the time period. The L-VOD index computed from SMOS observations allows sensing the whole canopy layer, while remote sensing observations made so far (including VOD indexes from high frequency microwave observations) were limited to sensing the top of the canopy, especially over relatively dense forests. In this study, the L-VOD index brings a temporal dimension to global, but static, maps of the above ground biomass.

An new tool to carry out an innovative monitoring of the dynamics of aboveground vegetation carbon stocks

This new method allows to monitor the seasonal dynamics of vegetation carbon losses and gains and also to link them with the impact of climate. The results demonstrate the key interest of SMOS L-VOD as a complementary data source for the quantification and monitoring of carbon stocks for national reports and large scale efforts in the framework of international initiatives such as the United Nations Framework Convention on Climate Change (UNFCCC) and the Intergovernmental Panel on Climate Change (IPCC). The SMOS L-VOD index is particularly relevant to study relatively dense vegetation ecosystems where the signal measured from other remotely-sensed system saturates. It is also very relevant for semi-arid regions with little inventory data.

First applications of the new L-VOD tool to monitor carbon changes in sub-Saharan Africa

The study demonstrates there is an overall negative net carbon budget for sub-Saharan Africa (−0.10 PgC yr−1) over 2010-2016 and that the majority of the net losses occurred in drylands. In the latter regions, the gross loss per year represents approximately

5% of the dryland total carbon stocks in Africa. Overall, most of the detected decreases in carbon stocks in drylands were related to abnormally low soil moisture and rainfall conditions. The analyses showed there is a high inter-annual variability in the vegetation carbon stocks with gains during very wet years in (2011) and losses during in 2015 and early 2016, following a severe El Niño episode.

This study questions the general understandin

g that drylands may serve as carbon sinks on the long term. Indeed, the authors have found that dry years have partly reversed this trend and that drylands (especially in southern Africa) turned from being a carbon sink into a source over 2010-2016, demonstrating that climate controls short-term variations in carbon stocks at large scales.

So, in the long term we need to reassess whether woody vegetation in African savannahs will continue to be a carbon sink.


1 Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark

2 List of French teams involved:

Unité « Interaction Sol Plante Atmosphère » (Inra, Bordeaux Sciences Agro), centre Inra Nouvelle-Aquitaine

Laboratoire Evolution et Diversité Biologique (CNRS – IRD – UT3 Paul Sabatier – ENFA)

Laboratoire des sciences du climat et de l’environnement (CEA-CNRS-UVSQ)

Centre d’études spatiales de la biosphère (Cnes-CNRS-IRD-UT3 Paul Sabatier)

Research Engineer in Remote Sensing: Characterising Uncertainties in Satellite Sea Surface Salinity

Category : Ocean, position opening

A research engineer position is open at the Laboratoire d’Océanographie et du Climat – Expérimentation et Approches Numériques (LOCEAN)/ Institut Pierre Simon Laplace (IPSL), PARIS, starting as soon as possible. The position is open for one year, renewable for 2 years depending on the candidate performance.

Context:

The SMOS (Soil Moisture and Ocean Salinity) mission is the first Earth-observing satellite mission carrying an L-band radiometer interferometer. Since its launch at the end of 2009, it has acquired more than 8 years of data that demonstrate the feasibility of the sea surface salinity retrieved by satellite with remarkable spatial resolution compared to other techniques. It has also opened new research perspectives. This unique 8-year salinity time series has permitted unique analyses of salinity variability, linked to oceanic meso-scale and to El Niño type events. Two other satellite missions, Aquarius (2011-2015, CONAE/NASA) and SMAP (2015-, NASA), also based on L-band radiometry, have been providing complementary synoptic salinity measurements leading to an unprecedented spatial coverage. Nevertheless, uncertainties on retrieved salinities differ depending on the radiometer type, the observation geometry, the calibration method, and on the direct and inverse models.

The LOCEAN team is involved since 1999 in the definition of the direct and inverse models applicable to SMOS and in the calibration-validation of the SMOS measurements. It is recognized as SMOS expert support laboratory by the European Spatial Agency (ESA) and by the Centre Aval de Traitement des Données SMOS funded by Centre National d’Etudes Spatiales (CNES). The selected candidate will join the LOCEAN team involved in the physics of the L-band radiometry, in the satellite salinity validation and in the understanding of responsible processes for the observed differences between satellites and in situ measurements, in particular those associated with air-sea interactions, vertical stratification and small-scale variability (www.locean-ipsl.upmc.fr/smos/ and siss.locean-ipsl.upmc.fr).

Work details :

- Characterization of uncertainties of satellite salinity products based on intercomparisons of the various satellite products and comparisons with in situ measurements. This work will be based on existing tools that the selected engineer will adapt to focus on case studies allowing the identification of the uncertainties origin. It will be performed in strong collaboration with researchers and engineers of the LOCEAN SMOS team.

- SMOS data processor development assessment in collaboration with the engineers and researchers in charge of its evolution. Participation to regular progress meetings (teleconferences) of CATDS (2-3 per year).

- Support to users (in French and English)

-Writing of technical papers and participation to scientific papers is possible, depending on the obtained results.

Required Skills:

-       Physics of satellite measurement

-       Data statistical analysis and critical interpretation of the results

-       Autonomy and team collaborative working

-       Python / Matlab ; LINUX

-       Interest in team software development: object-oriented programming, code refactoring & automated testing (e.g. pytest), version control (e.g. Git), code documentation.

Appreciated Skills:

-       Optimization for large dataset processing

-       Interest for environmental science

-       French and English

Level: Research Engineer (PhD thesis or equivalent). Master 2 in remote sensing will also be considered.

Address : LOCEAN, Sorbonne Université, Tour 45-55, 5E, 4, place Jussieu, 75005 PARIS, FRANCE.

Salary : about 1900E monthly net, commensurable with qualification and experience of the candidate (CNRS salary grid)

Candidates should send a statement of interest, CV and coordinates of 2 referees to  Jacqueline Boutin (jb@locean-ipsl.upmc.fr) and Dimitry Khvorostyanov (dimitry.khvorostyanov@locean.upmc.fr ).

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