Problems and solutions of thermal infrared remote sensing for drought-monitoring

China suffers more from droughts every year than from floods, especially in the Huang-Huai-Hai Plain and Sichuan Basin where grain yield is essential to support large local population and the nation's economy as well. However, it has been an unsolved problem to accurately evaluate the degree of drought over the vast area, so precious water resource and mitigation funds can hardly be allocated effectively. Therefore, large area drought monitoring has been a significant part of China's program "Remote Sensing Monitoring and Evaluation System for Severe Natural Disasters". In this system, various models of daily evaporation and soil's thermal inertia have been developed and employed. However, reliable evaluation of drought needs true land surface temperature (LST), or even better, true temperatures of leaf canopy and background soil as inputs for model inversion. Unfortunately, remote sensing (RS) of LST is a very challenging problem at present development stage of technology. On the coming next generation of RS satellites, there will be advanced thermal infrared (TIR) sensors such as MODIS ASTER, or GLI. Tremendous efforts have been devoted to atmosphere correction and temperature emissivity separation (TES) for new LST product algorithms. However, the mechanism of directionality of thermal emission from land surface remains unsolved, thus the targeted accuracy can hardly be achieved. Partly in order to improve China's RS system for drought monitoring, China's Ninth Five-Year Plan for Key-Important Basic Research (1996-2000) decided to have a project investigating the problems in LST RS and looking for solutions. Meanwhile, the BRDF (Bi-directional reflectance distribution function) which we have been working on is very promising to provide possible solutions with needed structural information

Extraction of nonlinear hysteretic properties of seismically isolated bridges from quick - release field tests

A time domian system identification method is used to identify the hysteretic properties of lead-rubber bearings installed in seismically isolated bridge systems. The longitudinal or transverse motion of the superstructure is idealized as a single degree of freedom (SDOF) system, where the total damping effect has been divided two parts.