In-line Typed High-Precision Polarization Lidar for Disaster Prevention

Abstract

Prediction of local and steep weather change such as heavy rain and lightning strike are urgently needed for disaster prevention. In Japan, Automated Meteorological Data Acquisition System (AMeDAS) has been operational throughout the country, with a mesh size of 20 km. Lightning Location Positioning (LLP) system, Lightning Position and Tracking System (LPATS), and SAFIR (Surveillance et Alerte Foudre par Interferometrie Radioelectrique) have been also used for lightning detection. (MacGorman & Taylor, 1989; Thery, 2001; Hayashi, 2006; Matsudo et al, 2007; Hauf et al, 2007) All of these weather observation systems, however, are comprehensive and necessary to analyze the multipoint data for the weather forecast in a certain area. Heavy rain and lightning strike locally occur during a short time period. They are often broken out at low-altitude and mainly caused by ice-crystals in cloud. Such local and steep weather change should be observed and be distinguished at a point observation. Radar (Radio Detection and Ranging) is a solution to catch weather change, but it can only detect rain droplets and cannot detect cloud particles which are precursors of heavy rain. To predict the heavy rain and lightning strike, low-altitude atmosphere and cloud should be observed. Furthermore, the flow of ice-crystals should be monitored. Lidar (LIght Detection And Ranging) can observe the atmosphere and cloud. It is standalone system and can distinguish ice-crystals from water droplets. On the other hand, Lidar technique is unsuited for observation in the near range because the laser beam will be dangerous for human eye. To develop the disaster prediction system for local weather change, we apply the lidar technique. The system was designed with emphasis on the following characteristics: Stand-alone Compactness Eye-safety To realize such a system, in-line optics, or common optics for transmitter optics and receiver optics, was adopted. It is usual technique for microscope optics, while the pulsed energy on lidar is too high that no one could accomplish its development since the first proposal. (Measures, 1984) Micro Pulse Lidar (MPL) broke though the problem and built up the new generation in lidar field. (Spinhirne, 1993, 1994 & 2001; Grund & Sandberg, 1996; Lee et al, Source: Advances in Solid-State Lasers: Development and Applications, Book edited by: Mikhail Grishin, ISBN 978-953-7619-80-0, pp. 630, February 2010, INTECH, Croatia, downloaded from SCIYO.COM