tailieunhanh - Radio Propagation and Remote Sensing of the Environment - Chapter 14

Các đặc điểm chính của bề mặt nước được xác định bằng các phương tiện kỹ thuật viễn thám là nhiệt độ bề mặt, độ mặn, độ nhám, tài sản lớp băng bao phủ, tính chất của màng mỏng trên bề mặt nước, hình thức geoid, và địa hình (Hình ). Các thay đổi nhiệt độ bề mặt đại dương trong một loạt các -1,9 đến +30 ° C. Các giá trị tối đa của nhiệt độ được quan sát giữa vĩ độ 5 ° và 10 ° phía bắc. Nhiệt độ tối thiểu là điển hình cho các vùng. | 14 Water Surface Research by Radio Methods GENERAL PROBLEMS OF WATER SURFACE REMOTE SENSING AND BASIC A PRIORI INFORMATION The main characteristics of water surface determined by means of remote sensing techniques are surface temperature salinity roughness ice cover properties properties of thin films on the water surface geoid form and topography Figure . The ocean surface temperature changes within a range of to 30 C. The maximal value of temperature is observed between latitude 5 and 10 north. The minimal temperature is typical for waters of the Arctic basin. The variation in daytime temperature seldom exceeds C. As a rule the properties of water surfaces topographies and physico-chemical characteristics are statistically homogeneous which makes them very convenient for the application of remote sensing technology. As we have established the interaction of radiowaves with surfaces is determined by the dielectric permittivity of the medium bounded by the surface and depends on the topography particularly the roughness of the studied surface. As for water permittivity the Debye formula see Equation is augmented by a term representing the conductivity e . w CoT s - o 1 J p _ r s o 2 Ầ 1 1 c The terms o s and are explained in Chapter 12 and Ơ is the water conductivity. All parameters depend on the water temperature and its salinity. Various approximation formulae can be used. We will take advantage of the formulae given by Rabinovitch and Melentjev97 to which we add salinity terms. These formulae have the form o _ s _ - Xr _ - - Ơ _ S 1 . 377 2005 by CRC Press 378 Radio Propagation and Remote Sensing of the Environment REFFERENCE ELLIPSOID CENTER OF MASS FIGURE Main characteristics of a water surface as determined by means of remote sensing. Here the temperature t T - is expressed on the Celsius scale and salinity 5 is expressed