La Nina is a natural 3-6-year cycle, and the cold stretch of a periodic thermal oscillation in ocean surface temperatures that occurs throughout the tropical Pacific.
拉尼娜每隔3到6年发生一次，太平洋热带地区海水温度会随之发生周期性的异常变冷。
2
Firstly, it directly influences the periodic variation of precipitation and air temperature, then influences the periodic variation of runoff based on the underlying surface.
天体运动直接影响降水和气温的周期变化，进而在一定的下垫面条件下，影响径流的周期变化。
3
Theoretical analysis, numerical calculation and experimental study are tarried out for this kind of antenna, by use of the theory of two-dimensional periodic admittance surface.