New inversion method for snow density and snow liquid water content retrieval using C-band data from ENVISAT/ASAR alternating polarization in alpine environment

Mohamed Niang, J. P. Dedieu, Y. Durand, L. Mérindol, M. Bernier, M. Dumont

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

This study presents a new method to analyse some parameters of snow in alpine region: density, wetness. Here are developed the methodology and first results obtained from a set of ASAR-ENVI SAT images registered during 2004 spring period over an experimental river basin located in the French Alps (N 45° 05'/ E 6° 10'). For ENVISAT/ASAR data, a topographic processing is done using a Digital Elevation Model (DEM) in order to correct the strong slope effects and determine the local incidence angles. During each ENVISAT data acquisition, intensive field measurements of snow pack properties (snow lines, snow pits) and weather conditions were gathered on 7 representative test sites. We propose a new inversion method for snow wetness and snow density retrievals by assimilating times series of ENVISAT/ASAR Alternating Polarization data. We use a forecast snow parameters and the covariance of the forecast error in order to produce inferred parameters compatible with the radar satellite measurements. An iterative method is set to find the maximum probably solution to a non-linear retrieval problem. This performs an inversion of the backscattering signal in VV and VH polarizations to retrieve simultaneously the snow liquid water content and snow density. This method provides a powerful tool since it consists in: 1) a fully physical method, involving calculations for each snow profile of corresponding backscattering signal by the 'forward model' in VV and VH polarization (and of derivatives of backscattering with respect to profile parameters); and 2) a statistical method, since it uses the covariance of forecast error as a constraint. The theory of this new approach is presented and the application to ENVISAT/ASAR data is discussed. Error characteristics of this method are investigated. The results of using as 'the first guess' as the snow characteristics profile given by the distributed SAFRAN/CROCUS snow model (Météo-France) are presented. The results are very satisfactory. Furthermore, for the wet snow condition in alpine environment, an appropriate methodology to have accurate radar measurements and simulated backscattering is proposed.

Original languageEnglish
Title of host publicationEuropean Space Agency, (Special Publication) ESA SP
EditionSP-636
Publication statusPublished - Jul 2007
Externally publishedYes
EventEnvisat Symposium 2007 - Montreux, Switzerland
Duration: 23 Apr 200727 Apr 2007

Other

OtherEnvisat Symposium 2007
CountrySwitzerland
CityMontreux
Period23/4/0727/4/07

Fingerprint

Snow
Water content
Polarization
Liquids
Backscattering
Radar measurement
Springs (water)
Iterative methods
Catchments
Time series
Data acquisition
Statistical methods
Radar
Rivers
Satellites
Derivatives

ASJC Scopus subject areas

  • Aerospace Engineering

Cite this

Niang, M., Dedieu, J. P., Durand, Y., Mérindol, L., Bernier, M., & Dumont, M. (2007). New inversion method for snow density and snow liquid water content retrieval using C-band data from ENVISAT/ASAR alternating polarization in alpine environment. In European Space Agency, (Special Publication) ESA SP (SP-636 ed.)

New inversion method for snow density and snow liquid water content retrieval using C-band data from ENVISAT/ASAR alternating polarization in alpine environment. / Niang, Mohamed; Dedieu, J. P.; Durand, Y.; Mérindol, L.; Bernier, M.; Dumont, M.

European Space Agency, (Special Publication) ESA SP. SP-636. ed. 2007.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Niang, M, Dedieu, JP, Durand, Y, Mérindol, L, Bernier, M & Dumont, M 2007, New inversion method for snow density and snow liquid water content retrieval using C-band data from ENVISAT/ASAR alternating polarization in alpine environment. in European Space Agency, (Special Publication) ESA SP. SP-636 edn, Envisat Symposium 2007, Montreux, Switzerland, 23/4/07.
Niang M, Dedieu JP, Durand Y, Mérindol L, Bernier M, Dumont M. New inversion method for snow density and snow liquid water content retrieval using C-band data from ENVISAT/ASAR alternating polarization in alpine environment. In European Space Agency, (Special Publication) ESA SP. SP-636 ed. 2007
Niang, Mohamed ; Dedieu, J. P. ; Durand, Y. ; Mérindol, L. ; Bernier, M. ; Dumont, M. / New inversion method for snow density and snow liquid water content retrieval using C-band data from ENVISAT/ASAR alternating polarization in alpine environment. European Space Agency, (Special Publication) ESA SP. SP-636. ed. 2007.
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