Future performance of ground-based and airborne water-vapor differential absorption lidar. I. Overview and theory

The performance of a future advanced water-vapor differential absorption li dar (DIAL) system is discussed. It is shown that the system has to be a dir ect-detection system operating in the rho sigma tau band of water vapor in the 940-nm wavelength region. The most important features of the DIAL techn ique are introduced: its clear-air measurement capability, its flexibility, and its simultaneous high resolution and accuracy. It is demonstrated that such a DIAL system can contribute to atmospheric sciences over a large ran ge of scales and over a large variety of humidity conditions. An extended e rror analysis is performed, and errors (e.g., speckle noise) are included t hat previously were not been discussed in detail and that become important for certain system designs and measurement conditions. The applicability of the derived equation is investigated by comparisons with real data. Excell ent agreement is found. (C) 2001 Optical Society of America.