Geografie 1978, 83, 91-103
The Degree of Irregularity of the Annual Variation of Precipitations
The annual variation of precipitations as an important, geographically typical characteristics of a region has been studied by means of different methods. One of them is the method presented by C. G. Markham (1970) and elaborated by C. A. Shverova (1973, 1975, 1976) based on the vector expression of the annual variation of precipitations (Example see in Fig. 1) and characterising it by means of two indices: the degree of irregularity of the annual variation of precipitations marked by F (also seasonality index) and the occurrence of the month of the concentration of precipitations. The characteristics mentioned are very suitable for the cartographic representation of the annual precipitation period (see Fig. 2) and for expressing the rate of continentality of the annual variation of precipitations. As shown by the values of index F (Fig. 2), the most oceanic character of the yearly distribution of precipitations (i. e., the most balanced annual variation) can be found in the border mountain ranges of Bohemia, where the values of the index of irregularity F drop below 10 % and the month of precipitation concentration falls to the second half of September and to the autumn months. On the other hand, the most continental features in the distribution of precipitations throughout the year are those of the stations in the Bohemian Vale and in the north of Moravia. It is mainly due to very low winter precipitations (the leeward positions of those regions). The month of precipitation concentrations there is July. The values of index F are above all influenced by the regional factor (particularly the exposition of the region) which is in iteration with the orographic factor. In this connection height above sea level plays a minor part. With its growing value the index values change parabolically, i. e., the highest positioned stations have a less balanced annual variation than those with the height above sea level from 800 to 1 000 m which, by the distribution of precipitations in the course of year, are the most oceanic. The above characteristics of the annual variation of precipitations are suitable for ranking the stations to the individual types of the annual variation, as follows from Tab. 3, and for the comparison of stations with one another. The author of the present paper is looking for the connection between the irregularity index of the annual variation of precipitations as a non-traditional climatic index and the vegetation degrees on the territory of the C.S.R. (Fig. 4, Tab. 4). The values of the irregularity index prove to drop from the stations belonging to the beech degree in essence till the stations belonging to the spruce-beech-fir and or spruce degrees. At the same time it is evident that the annual variation of precipitations is only one of climatic factors participating in the space distribution of the plant cover.
