Abstract
In order to obtain some information concerning the relationship between the blocking action and the effects of mountains and land-sea distribution, numerical experiments were performed with four models. One of these models includes both the effects of mountains and land-sea distribution, two models contain one or the other and the remaining model neither of them.
The statistical analysis of the results thus obtained leads to the following conclusions:
1. Even in the case including neither the effects of mountains nor land-sea distribution, blocking action occurs and its behaviour is very similar to that observed in the actual atmosphere.
2. The duration period of blocking action in the model atmosphere is remarkably short compared to that in the actual atmosphere. However, there is a tendency for the duration period to become somewhat longer if the effect of mountains is included in the model.
3. The most frequent existence of blocking highs in the areas from 150°E eastward to 150°W (including Alaska) and from 30°W eastward to 30°E (including the Atlantic) results from the effect of mountains. An additional incorporation of the effect of land-sea distribution contributes to yielding the result that the blocking highs are more frequently bound in the area from 30°E eastward to 150°E (including the Eurasian Continent) than in the area from 150°W eastward to 30°W (including the North American Continent).
4. It is not likely that the effects of mountains and land-sea distribution play a major role in bringing about the fact that blocking highs exist most frequently in the latitudinal belt between 50°N and 70°N in the actual atmosphere.
