The onset of the summer monsoon over the South China Sea is studied by the global spectral model(T42L9) of the Institute of Atmospheric Physics. The onset of the summer monsoon over the South China Sea is closely related to the intense convergence at 850hPa over the South China Sea, which is constituted by the cross-equatorial southerly divergent wind over the eastern Indian, the westerly divergent wind along the southern flank of the Tibetan Plateau, the northerly divergent wind along the eastern periphery of the Plateau, and the easterly divergent wind of the Western Pacific. Various sensitive numerical model experiments show that latent heating of the Southeast Asia and the dynamic effects of the Tibetan Plateau are both very important to those four divergent airstreams and that convergence.

In electron optical system, electron beams emitted by cathode will be focused and deflected by electron optical system, and then it will hit the screen with small size. Because deflection system has deflection aberration, the electron beam that is focused into one point in the centre of screen will not be focused well in the corner of screen, and it will become a circle spot. Because decison of the spot quality on the screen is ac, this paper described the hay research for electron optical syStem quality.The spot size on screen is changed with the changing of screen location, so the' electron optical system quality is receded fuzzily when screen location is changed. According to these fuzzy decisions, a best structure of electron optical system can be founded.