1. Assistant Researcher, Dept. of Hydraulic Engineering, Tsinghua Univ., Beijing 100084, China.
2. Staff Scientist, Atmospheric, Earth, and Energy Division, Lawrence Livermore National Laboratory, Livermore, CA 94551.
3. Professor, Dept. of Hydraulic Engineering, Tsinghua Univ., Beijing 100084, China (corresponding author).
4. Distinguished Professor, Dept. of Civil and Environmental Engineering, Univ. of California, Davis, CA 95616; Emeritus Professor, School of Applied Mathematical and Physical Sciences, National Technical Univ. of Athens, Greece.