This book considers the formation of the signal reflected from the sea surface when sensing in the radio and optical range. Currently, remote sensing from space is the main source of information about the processes taking place in the atmosphere and ocean. The correct interpretation of remote sensing data requires detailed information about the rough surface that forms the reflected signal. The first three chapters describe the statistical and spatial-temporal characteristics of the sea surface, focusing on the effects associated with the nonlinearity of sea surface waves. The analysis makes extensive use of data obtained by the authors on a stationary oceanographic platform located on the Black sea. In the next seven chapters, the authors analyze how the nonlinearity of waves affects the formation of a signal reflected from the sea surface.