L Band continuation workshop update

Category : Non classé

Just a few words to say that the L band continuation workshop is now well over. We are preparing some documents and most notably a white paper. We will also put on this blog a post summarising the main findings…

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L band continuation workshop for the last day (Pic by A. Al Bitar)

This last week several of us attended also the ESA/ECMWF workshop at ECMWF, complementing usefully the findings of the previous week.

So stay tuned!

L Band Continuation workshop is on at CESBIO

Category : Non classé

Hello all

The L band continuation workshop is currently underway at CESBIO the agenda is
Agenda_workshop20171027

Yesterday, the presentations and exchanges were put on line by Ahmad and can be seen here.

We will continue today…

Interesting stuff from Davos (Laret) (for once?!)

Category : Data, ground measurements

Davos is well known for some meetings taking place up there. But our Colleagues from WSL and Gamma Remote sensing are carrying out a very interesting experiment as detailed below by Mike and Reza!

Davos-Laret Remote Sensing Field Laboratory: Latest Results and Progress

Reza Naderpour and Mike Schwank

The Davos-Laret Remote Sensing Field Laboratory (Switzerland) was established in October 2016 as the only currently-operating Alpine test site dedicated to the development of novel retrieval approaches for the estimation of snow properties from passive/active microwave remote sensing data.

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Caption: ELBARA in Davos-Laret: before winter (the wire mesh is visible on the ground) and when snow is present

The second winter campaign started on November 18, 2017 simultaneously with the publication of the first paper based on Winter 2016/17 campaign:

Naderpour, R.; Schwank, M.; Mätzler, C. Davos-Laret Remote Sensing Field Laboratory: 2016/2017 Winter Season L-Band Measurements Data-Processing and Analysis. Remote Sens. 20179, 1185.

Accessible here:

With two more upcoming papers, the research conducted in the Winter 2016/17 campaign has mainly investigated the retrieval of snow liquid water content from L-band radiometry as well as disturbing impacts of snow liquid water on the ground permittivity and snow density retrievals. Additionally, several data processing improvements, including a refined RFI mitigation approach, are suggested which can be of high interest to ELBARA users. See the PDF file for more information on the 2017/18 campaign and close-up details of the campaign practicalities!

NewsLetter_2017

(Very) soon 8 candles for SMOS!!!!!!! (7/8)

Category : Data, L2, L3, L4

After a look back at oceans, soil moisture and their applications let’s have a look at colder areas….

Actually during the SMOS early years we tried to get a cryosphere group  but with very limited success to say the least. Most of them were heavily involved with other missions with little time to spend on an L band radiometer of unfathomed relevance to their science.

But some had ideas and looked at the data very quickly… and the number of research topics rapidly grew! I will try below to give a few examples.

Of course there were some basic uses. Considering the L Band penetration depth in dry ice it was expected to ave a very stable signal in Antarctica suitable for vicarious calibration. While G. Macelloni and colleagues at IFAC implemented a radiometer at Dome Concordia, F Cabot used the site to verify SMOS calibration and sensitivity and after used it to inter-compare with Aquarius and SMAP (using SMOS capability to reconstruct their main lobe characteristics through reconstruction). He routinely monitors the L band radiometers in orbit and with M. Brogioni follows the absolute calibration through the ground radiometer.

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Caption: Temporal evolution of all sensors over Dome C (F. Cabot)

Over Antarctica several studies were performed (also funded by ESA) and products were made (available at CATDS) on estimation of internal ice-sheet temperature, estimation of ice thickness, indicator of the origin of ice-shelves variability, surface melting occurrences. But for me the most mind boggling result was obtained right at the beginning by Giovanni who identify definite signatures over lake Vostok which is some 3.7 km below the surface, while models indicate at best a 900 m penetration depth (G. Picard and M. Leduc Leballeur). Several potential explanations have been suggested but are yet to be validated.

Freeze thaw was expected to be a potential products and colleagues at FMI used the Elbara measurements in Sodankylä to devise a Freeze thaw algorithm. It is now quasi operational.

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Caption: Example for final soil freezing date on 2014 calculated from SMOS freeze/thaw data (K Rautiainen)

More novel the idea put forward by several scientists (G. Heygster, L. Kaleschke) to estimate thin sea ice thickness with SMOS. Now an operational product is being produced in Hamburg. It relies on the complementarity between Smos (sensitive below 75 cm thickness) and CryoSat only sensitive above a meter) the synergisms enable to track sea ice thickness globally whatever the thickness in a way, but also thin sea ice monitoring is a boon for ship routing around the Arctic (optimising between distance and ice to be broken through) and is of course very relevant for sea atmosphere exchanges.

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Caption: Temporal evolution of sea ice cover over the Arctic (L. Kaleschke)

Another ice cap of great interested is that of Greenland. The L band signatures are somewhat intriguing and several scientists are investigating it. But can already mention capturing significant melt event (as depicted by Mialon and Bircher on this blog) and some preliminary explanations for the different features seen.

Over land the first issue to tackle was that of the thick layers of organic soils whose dielectric constant are quite different from that of mineral soils (even the probes, if not calibrated properly, give wrong estimates). S Bircher and colleagues tackled the issue and developed both an improved dielectric model but also an adapted soils map to make good use of it. This constitutes a major step forward for the analysis of high latitudes. It will also lead to more adequate permafrost monitoring projects.

Finally I believe we are on the verge of another dramatic improvement with the very recent work done at WSL /Gamma by M. Schwank and colleagues and at FMI (K. Rautiainen and J. Lemmetyinen) as they found a way to infer snow density from SMOS data and then they are on the verge of extracting snow water content from L band radiometry.

For the cryosphere, these achievements and notably thins sea ice an snow density / water content are I believe very significant steps forward!

Stay tuned!

For further reading:

Bircher, S., Andreasen, M., Vuollet, J., Vehvilainen, J., Rautiainen, K., Jonard, F., Weihermuller, L., Zakharova, E., Wigneron, J.P., & Kerr, Y.H. (2016). Soil moisture sensor calibration for organic soil surface layers. Geoscientific Instrumentation Methods and Data Systems, 5, 109-125

Bircher, S., & Remote Sensing Editorial, O. (2017). L-Band Relative Permittivity of Organic Soil Surface Layers-A New Dataset of Resonant Cavity Measurements and Model Evaluation (vol 8, 1024, 2016). Remote Sensing, 9

Bircher, S., Demontoux, F., Razafindratsima, S., Zakharova, E., Drusch, M., Wigneron, J.P., & Kerr, Y.H. (2016). L-Band Relative Permittivity of Organic Soil Surface LayersA New Dataset of Resonant Cavity Measurements and Model Evaluation. Remote Sensing, 8

Kaleschke, L., Tian-Kunze, X., Maass, N., Beitsch, A., Wernecke, A., Miernecki, M., Muller, G., Fock, B.H., Gierisch, A.M.U., Schlunzen, K.H., Pohlmann, T., Dobrynin, M., Hendricks, S., Asseng, J., Gerdes, R., Jochmann, P., Reimer, N., Holfort, J., Melsheimer, C., Heygster, G., Spreen, G., Gerland, S., King, J., Skou, N., Sobjaerg, S.S., Haas, C., Richter, F., & Casal, T. (2016). SMOS sea ice product: Operational application and validation in the Barents Sea marginal ice zone. Remote Sensing of Environment, 180, 264-273

Lemmetyinen, J., Schwank, M., Rautiainen, K., Kontu, A., Parkkinen, T., Matzler, C., Wiesmann, A., Wegmuller, U., Derksen, C., Toose, P., Roy, A., & Pulliainen, J. (2016). Snow density and ground permittivity retrieved from L-band radiometry: Application to experimental data. Remote Sensing of Environment, 180, 377-391

Naderpour, R., Schwank, M., Matzler, C., Lemmetyinen, J., & Steffen, K. (2017). Snow Density and Ground Permittivity Retrieved From L-Band Radiometry: A Retrieval Sensitivity Analysis. Ieee Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 10, 3148-3161

Pellarin, T., Mialon, A., Biron, R., Coulaud, C., Gibon, F., Kerr, Y., Lafaysse, M., Mercier, B., Morin, S., Redor, I., Schwank, M., & Volksch, I. (2016). Three years of L-band brightness temperature measurements in a mountainous area: Topography, vegetation and snowmelt issues. Remote Sensing of Environment, 180, 85-98

Rautiainen, K., Parkkinen, T., Lemmetyinen, J., Schwank, M., Wiesmann, A., Ikonen, J., Derksen, C., Davydov, S., Davydova, A., Boike, J., Langer, M., Drusch, M., & Pulliainen, J. (2016). SMOS prototype algorithm for detecting autumn soil freezing. Remote Sensing of Environment, 180, 346-360

Ricker, R., Hendricks, S., Kaleschke, L., Tian-Kunze, X., King, J., & Haas, C. (2017). A weekly Arctic sea-ice thickness data record from merged CryoSat-2 and SMOS satellite data. Cryosphere, 11, 1607-1623

Schwank, M., Matzler, C., Wiesmann, A., Wegmuller, U., Pulliainen, J., Lemmetyinen, J., Rautiainen, K., Derksen, C., Toose, P., & Drusch, M. (2015). Snow Density and Ground Permittivity Retrieved from L-Band Radiometry: A Synthetic Analysis. Ieee Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 8, 3833-3845

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