8 H.WALTER 



be possible to give a detailed classification of all different climatic types 

 based on climatic data only and not on vegetative regions. Only then 

 shall we be able to carry out a true comparison between chmate and 

 vegetation. 



In Eastern Europe such a comparison shows that the border lines of the 

 vegetation regions (forest, forest steppe, steppe, semi desert) are much more 

 compHcated than the borders of the corresponding cHmatic regions. This 

 can easily be understood, as the vegetation depends not only on chmate but 

 also on soils. In a region with loess soils, steppe invades the forest belt in 

 tongue- or island-like extensions (Walter 1957). 



The borders between two vegetation regions are much sharper than 

 those between two chmatic types. In flat countries there is a steady transi- 

 tion from, one cUmatic type to another. A cartogram with climatic dia- 

 grams shows this clearly. Border lines on ordinary climatic maps in a 

 region of this type are, to a degree, misleading and arbitrary. 



All diagrams of the world atlas (about 10,000) are drawn in the same 

 manner, therefore it is easy to compare the climate of different stations. 

 The months are printed for stations on the Northern Hemisphere, starting 

 with January, those on the Southern Hemisphere starting with July, so the 

 warm season always comprises the middle of the diagram. This is necessary 

 to facilitate comparison. When confronted with the question where a 

 climate, corresponding to the climate of the Central Anatolian steppe, 

 might be found in other parts of the world by comparing different dia- 

 grams, it was easily possible to see that the climate of Ankara is similar to 

 that of Salt Lake City (U.S.A.) and Kabul (Afghanistan). In fact these three 

 places have a similar geomorphological situation and the vegetation of 

 these regions is equally similar. 



We hope that this atlas may prove useful in dealing with problems 

 concerning ecology, plant geography, agriculture, forestry and many other 

 fields of study. I wish to emphasise, that the figures in the diagrams are 

 exactly those pubHshed by the meteorological stations. Therefore, if 

 required, these data may be read from the diagrams. The diagrams comprise 

 only the most important cHmatic factors. Minute details should be avoided, 

 as the diagrams become overcrowded and consequently less clear. The 

 diagram gives only a rough idea of a climatic type. It is impossible to do 

 more, as even the most exact meteorological data do not correspond to the 

 plant climate, for they are, (i) measured in a screen, which means protected 

 from the radiation and (2) 2 m above ground. Moreover, only long-term 

 means are published. 



A normal climate, as given by the mean values, does not exist. There 



