The Study on the Microthermal Weather Process in the Lower Reaches of Yangtze River in Spring and Summer and Sudden Change of Triple-frequency Harmonic

In this paper, the microthermal weather process in spring and summer using wave spectrum data during 1971 to 1984 and energy spectrum data from May to July in 1972 through 1982 has been presented. It shows that the microthermal weather process often occurs in spring and summer, and it occurs most in April of spring and in July of summer. In the light of the analysis of the wave energy density spectrum, transport spectrum of momentum and angular momentum, divergent spectrum of momentum flux and index Ik and EOF expansion, the microthermal weather process in summer is closely related to the sudden change of triple-frequency harmonic. Therefore, sudden change of triple-frequency harmonic is a better indication of the microthermal weather process.