Some local characteristics of the refractive index which are needed for the research of microwave propagation are described in a general way.
The refractive indices on the surface and at 900 mb level are calculated with the use of the aerological sounding data. The vertical gradient of the refractive index is obtained by the use of these values.
The local values of the refractive index decrease towards north. The maximum values are located on about 30 degree zone of north latitude. On the open sea and at the end of the peninsulas, the vertical gradients of the refractive index have comparatively large values.
In the cold season, the gradient values on inland is larger than ones of the coastal stations, and in the warm season, the abovementioned situation is the opposite.
With the exception of Is. Hokkaido, the values of effective earth which is used in the theory of radio wave propagation are larger than the value got by the assumption of the standard atmosphere.
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