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Summary of Proposal COA2162

TitleStudy of coastal sea surface wind speed retrieval
Investigator Takeyama, Yuko - National Institute of Advanced Industrial Science and Technology, Information Technology Research Institute
Team Member
Dr Kozai, Katsutoshi - Kobe University, Graduate School of Maritime Science
Dr Ohsawa, Teruo - Kobe University , Graduate School of Maritime Science
SummaryIn this project, there are two subjects.Firstly, the accuracy in wind speed retrieved from TerraSAR-X images isexamined in Japanese coastal waters, Hiratsuka and Shirahama where there are offshoreobservation platforms. Secondly, factors of an underestimation of the SAR retrievedwind is clarified in coastal waters. It is reported that the coastal offshorewind is retrieved lower than the temporally synchronized in-situ measurement inprevious studies. But these studies are not enough to explain the reason whythe underestimation is caused in the SAR wind speed retrieval. It can beexpected that there are two kinds of factors in the underestimation. One is aneffect of an insufficient wind-wave growth. Capillary waves on the sea surfaceare gradually generated by friction velocities related to the sea surface wind.SAR may retrieve a lower wind speed when the capillary wave is not fullydeveloped. The other is an effect of planetary boundary layer (PBL)development. In coastal areas, the PBL height is dramatically changed. Thein-situ wind speed is measured at a height of an observation platform thoughSAR observes backscatters from the sea surface. The difference of observationheights may lead the underestimation in the SAR wind speed retrieval. In thisproject, accuracies of wind speeds retrieved by TerraSAR-X images are estimatedand in-depth process to make the underestimation in SAR wind speed is clarifiedusing not only TerraSAR-X but also ENVISAT/ASAR and ALOS/PALSAR images. ENVISAT/ASAR and ALOS/PALSAR images already havebeen obtained. The applicant already takes a Grant-in-Aid for ScientificResearch related to offshore wind resources assessments from the Japan Societyfor the Promotion of Science (No. 24760679). Thus, a cost for TerraSAR-X imageshas been already guaranteed.

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