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Summary of Proposal MTH3492

TitleMultifrequency estimation of soil moisture andDIScrimination of atmospheric phase delay based on SAR interferometry (DIS-SAR)
Investigator Nico, Giovanni - Consiglio Nazionale delle Ricerche (CNR), Istituto per le Applicazioni del Calcolo (IAC)
Team Member
Dr. Nico, Giovanni - Consiglio Nazionale delle Ricerche, Istituto per le Applicazioni del Calcolo
Prof. Catalao, Joao - Universidade de Lisboa, , Faculdade de Ciências, IDL
Mr. Conde, Vasco - Universidade de Lisboa, , Faculdade de Ciências, IDL
Dr. Mateus, Pedro - Universidade de Lisboa, , Faculdade de Ciências, IDL
SummaryThe main objectiveof the proposal is the estimation of temporal changes of soil moisture by SARinterferometry using X, C and L-band SAR images. To this end a key step is the discriminationof phase contributions in SAR interferograms due to the propagation inatmosphere, scattering on terrains with soil moisture levels changing in timeand temporal decorrelation in growing crops. Therefore, theaim of this project is twofold. On one side the project aims to develop andvalidate a methodology to discriminate phase contributions in SARinterferograms due to propagation in atmosphere and scattering by terrainsurfaces with different soil moisture content. We emphasize that for temporaldecorrelation we mean the regular drop of interferometric coherence in time,due a physical phenomenon such as the growth of crops or the soil moisture. Onthe other side, to reach this objective, the project need to demonstrate amethodology to discriminate the phase contributions due to propagation of SARsignal into troposphere and ionosphere (using L band SAR images) and use thisknowledge to derive time series of accurate maps of atmosphere’s PrecipitableWater Vapor with a spatial resolution of about 100 m, depending on the size ofthe filtering kernel, considered high in the community of atmosphere science,and assimilate these maps into a Numerical Weather Model to get more accurateforecasts of phase delay propagation in atmosphere at the time of SAR imageacquisitions. The use ofX-band SAR data, in addition to those that the research group is already usingin the C and L bands, will provide a better discrimination of thelong-wavelength atmospheric delays, related to both stratified and turbulenttroposphere from those related to soil moisture. Soil moisture willbe estimated using different methodology recently published in literature andbased on the use of SAR interferometry (e.g. see references [1]-[6] of nextsection on Detailed description). A comparison with traditional algorithmsusing in-situ measurements and SAR amplitude images will also be carried out[7]. A further factorwhich will also be investigated is the temporal decorrelation caused bychanging physical properties of the ground between acquisitions. Sudden andcomplete changes, e.g., due to agriculture practices or snow fall, areimpossible to model. Therefore, we will concentrate only on gradual and naturalchanges. Recently, it has been recognized that assuming the motion of thescatterers within a resolution cell as independent and equally distributed,estimates of the temporal decorrelation time constant is related to the regularvegetation growth. In particular, it has been observed that the decorrelationrate is slower and the more easily identifiable in the L band [7]. The temporalconstant of decorrelation contains information on the phenomenon causing such aslow and regular decorrelation. This kind of decorrelation is different fromthe usual interferometric decorrelation caused by either large spatial baselineor long temporal baselines. This important result can also be useful toidentify and subtract local phase components on the interferograms related tothe vegetation growth in agriculture fields. This projectwill lead to the following results: 1) Algorithmsand software for the mapping of temporal changes of soil moisture; 2.) Validationwith in-situ measurements of soil moisture The results ofthis project are expected to constitute a valuable tool for agriculturalpractices and the integrated management of water resources in areascharacterized by hydric stress. The researchwill be carried out with internal fund of the two involved research institutes.ALOS-2 SAR images will be providedwithin the JAXA project “Disentangle troposphere, ionosphere and soil moisturecontribution in the SAR interferometry (PI 3110). The project will extend for 2 year and will use archive images acquired form TerraSAR.

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