tailieunhanh - Geoscience and Remote Sensing, New Achievements Part 9

Tham khảo tài liệu 'geoscience and remote sensing, new achievements part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Ocean wind fields from satellite active microwave sensors 273 resolution of about 10 km in latitude and 7 km in longitude higher than that of scatterometer km by km its fields result smoother. This common feature of the model fields discussed in Chèruy et al. 2004 and Skamarock 2004 stresses the importance of the satellite winds in studying the mesoscale spatial features of the wind. 4. Small-scale structure of the MABL from SAR images The increased availability of satellite SAR images offers to scientists many opportunities to investigate the structure of the MABL over the sea and coastal areas. Scientific literature about SAR images over the ocean has shown a variety of geophysical phenomena detectable by SAR Alpers Brummer 1994 Kravtsov et al. 1999 Mitnik et al. 1996 Mityagina et al. 1998 Mourad 1996 Sikora et al. 1997 Zecchetto et al. 1998 including the multiscale structure in the atmospheric turbulence under high winds and the structure of the convective turbulence under low wind. More recently some effort has been devoted to evaluate the wind direction using the backscatter signatures produced by the atmospheric wind rolls or those occurring at the lee side of islands Vachon Dobson 2000 as effect of wind shielding by computing the local gradient of the image backscatter Horstmann et al. 2002 Koch 2004 or by using the two dimensional Continuous Wavelet Transform CWT2 Zecchetto De Biasio 2002 Zecchetto De Biasio 2008 . This section illustrates the ability of the CWT2 in detecting and quantifying the backscatter pattern linked to the spatial structure of the MABL. It summarizes the CWT2 methodology applied to SAR images providing the results obtainable by showing a case study chosen among the hundreds of images analyzed. The extraction of the wind field from SAR images a follow up of the CWT2 analysis is then illustrated at the end. The methodology The Continuous Wavelet Transform Beylkin et al. 1992 Foufoula-Georgiou Kumar 1994 f of a function