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Agro-climatic Atlas of Europe
AgriculturalMeteorology- ElsevierPublishingCompany, Amsterdam- Printed in The Netherlands
Book Review Agro-climatic Atlas of Europe. (Vol. 1 of a three-volume work: Agroecological Atlas of Cereal Growing in Europe.) P. THRAN and S. BROE~HUIZEN.Pudoc, Wageningen--Elsevier, Amsterdam, 1965, 294 pp., 128 maps, Dfl.95.00, £ 9.10.0. The first volume of an atlas-series called Agroecological Atlas of Cereal Growing in Europe has recently appeared under the heading: Agro¢limatie atlas of Europe. The volume is prepared by Dr. P. Thran from Kiel and Mr. S. Broekhuizen from Wageningen, both well-known specialists in the application of weather data to studies of agricultural potentialities. The series is published by Elsevier Company, Amsterdam. In connection with a review of an agro-climatic atlas of this kind, it might be worthwhile first to consider for a moment the definition of agro-climatology and those methods which should preferably be applied in this field. First of all we must remember that there is a difference between agro-meteorology and agro-climatology as in a similar way between meteorology and climatology. Agro-meteorology is the overall subject aiming at investigating the nature of the physical processes in the air which are related to the development of agricultural species. These physical processes are basically observed by measurements at ordinary meteorological stations of various elements such as radiation, temperature, evaporation, precipitation etc. The data obtained may be used for a direct correlation with simultaneous phenological observations of plant development in order to understand the interrelation between the physical and the physiological processes. However, such observations usually are not very well suited for this application, taken as they are at a height of 2 m above the ground and not in the air layer which is directly in contact with the plants. Moreover, it is not possible to consider the influence of turbulence processes on plant development by the use of such macro-meteorological data. Therefore the micro-meteorological approach has become particularly useful in agro-meteorology as the relevant elements with such an approach are observed in the lowest air layers of the atmosphere which are in direct contact with the plant. By observations of the gradients of various elements with height, the turbulence aspect may also be considered. The application of micro-meteorological data to plant development has often been referred to as micro-climatology or agro-climatology, but as will be clear from the definition of these terms given below this can not be so. Ordinary meteorological observations at a height of 2 m above the ground, although not very suitable for direct studies of the physical processes at plant-level are, however, quite useful for the climatological approach to agricultural problems. This approach implies a statistical treatment of the variation in time and space of meteorological and phenological data aiming at establishing empirically, but not by processes, the existing interrelations between meteorological factors and plant development. Consequently agro-climatology works with parameters such as mean values, frequencies, intensities, dependencies and probabilities of meteorological elements selected and calculated for periods of time so as to suit the study of inter-
Agr. Meteorol., 3 (1966) 263-266
264
BOOKREVIEW
relations with plant-development. The space aspect of this kind of statistics is usually taken into consideration by mapping these parameters for the periods applied and using them for some sort of agro-climatic classification of landareas. Of course micro-meteorological data may also be treated statistically for periods suitable for understanding the relationship with plant development. Furthermore approximative or empirical equations may be derived to determine statistical values of various elements over longer periods of time. Such treatments of micro-meteorological data, but only these, should be considered as part of agro-climatology rather than agro-meteorology. The above definitions seem to imply that the most suitable approach to the whole subject of agro-meteorology would be to establish first of all the interrelationship between physical and physiological processes and only later to calculate and map the climatological parameters when parameters and periods of time may be selected in view of the results obtained by the physical approach. The climatological approach was taken up long before the physical one, due to its much easier application and consequently it has given a considerable amount of results which have been very useful throughout the years. It must be kept in mind, however, that recently so many advanced studies of the physical processes in relation to plant physiology have taken place that modern agro-climatology should now, as far as possible, take results from those studies into consideration. In other words we are now better equipped than earlier to decide which parameters are useful for agroclimatological treatments, taking into consideration the results obtained in investigations with a physical approach to the subject. In his introduction to the atlas under review, Dr. Thran has outlined quite clearly that the intention of the atlas is to outline the climatological foundations for European agriculture. This task, of course, is a typically agro-climatological one in accordance with the definitions given above. The first question that arises in this connection is that asking which elements should be mapped to present an adequate outline. It seems possible that in this selection a more modern approach making use of our knowledge of the physical processes might have been useful. On the other hand there is no doubt that the vast majority of the maps presented are valuable and essential as an adequate basis for the outline. Lack of space does not allow me to discuss those maps which can be accepted as essential, so I shall only bring up for discussion some of them which seem questionable to me. The first map to be discussed is the one showing agro-climatic sub-provinces in Europe. First of all it is doubtful whether the provinces, which have resulted from a rather peculiar method of mixing all boundaries known from various classifications of climate in Europe, may be called agro-climatic. As far as it is possible to judge from the very brief text on the method, there is no clear interrelation between the climatic parameters applied and agricultural conditions. Therefore the result of this "mixing of classifications" is a new climatic classification where the provinces show similarities with regard to various climatic parameters which from the agricultural Agr. Meteorol., 3 (1966) 263-266
BOOK REVIEW
265
point of view seem arbitrarily chosen. There are many other parameters mapped in the atlas which seem much more relevant for a classification than those chosen from K6ppen, Hettner, Blair, etc. For instance the use of those parameters showing climatic conditions during the growing season as well as frequencies, intensities and water balance conditions would have given a more sophisticated classification. The selected method has given us a simplified climatic picture of Europe which is based only on primary and fundamental climatic parameters. It may be useful to agriculturists without being in my opinion particularly suitable to them. It should be added that this climatic classification can hardly be accepted by modern climatologists who would like to see climate classified by means of parameters which give a clear idea of the physical processes involved. A modern classification should, in other words, be based on the genesis of climate, i.e., should be derived from the general circulation of the atmosphere or from other parameters which give a clear picture of the space and time variations in physical processes of the atmosphere. As far as the practical usefulness of the classification is concerned, it seems probable that it would also have increased considerably if a clear description of the reason for selecting the parameters and of their possible interrelation with agriculture could have been added in the text. As to the map itself, it may be noted that the grey colours are too much alike and difficult to separate from each other. Proceeding now to the maps showing numerical values of various parameters derived for basic climatic elements such as temperature, precipitation and evapotranspiration there can be no disagreement that they on the whole represent an excellent contribution which will be most useful to various aspects of applied climatology. In many cases new maps with data never presented earlier are given in this atlas. However, here again one wonders why there is no accompanying text where indications could have been given about how to apply these parameters to agriculture, i.e., again to explain the basic agro-meteorological reasons for the selection of just these parameters. Anybody who is not very familiar with agro-climatology will put this question and unfortunately will not get any answer. Another question that most users of this atlas will put is why no isolines are drawn on the maps. Most problems facing the agriculturist will be to which extent a certain value given on these maps is representative to the surroundings of the place where the value is derived. A climatologist certainly has better qualifications to judge about the representativeness than anybody else. The most suitable and simplest way for him to give an indication of the influence of topography and other geographical complications is to draw isolines for certain threshold values. Such isolines therefore would have increased the value of the atlas considerably. I should like to question a few reasons for some of the maps presented. For example, what is the reason for including a map of the difference between average monthly maximum of the warmest month and average monthly minimum of the coldest month when two more useful parameters to show the annual amplitude of monthly mean temperatures of the air are already given. There is no indication, as far as I know, that this difference as such has any agricultural implication.
Agr. Meteorol.,3 (1966) 263-266
266
BOOK REVIEW
It is a pity that no values of precipitation days were available for all Scandinavia. With some luck the authors could have obtained these values from the meteorological services in the Nordic countries where they are certainly available. Map 371, showing a general survey of the average annual potential evapotranspiration in Europe, is an important contribution to this atlas as it maps a parameter which we know now is essential to agriculture. It is taken from a publication by Mohrmann and Kessler who have studied the water deficiencies in Europe by means of Turc's formula. However, the reviewer has not been able to ascertain whether it is really the potential evapotranspiration which is mapped as said in the title or rather the actual evapotranspiration. There is no doubt that the formula by Turc given on the map generally gives the actual evapotranspiration but with a certain fixed value of the crop factor V it gives the potential evapotranspiration. Without an accompanying explanation it is here again impossible to understand completely the intentions of the authors. Either if this map gives the potential or actual annual evapotranspiration, it would have been worthwhile to apply the formula to some more stations as the map, as it is now, gives too few details, particularly for the northern part of Europe. A general comment on the maps reproduced from Mohrmann and Kessler's work is that they are difficult to understand, and interpret without studying the original paper, because in the atlas there is no indication or text about how water deficiency is defined and calculated. As emphasized earlier, this last comment could be generalized to apply to the whole atlas and it seems to include a rather serious criticism. The authors obviously have thought that by presenting their maps in an atlas intended above all for statisticians and agriculturists who are not specialists in climatology, there was no need for clear explanations to be given about how the maps were prepared. This seems a serious mistake because as they are now presented., it is impossible to judge the representativeness and accuracy of the data. There is no discussion about the basic material used for the preparation of the maps, nor is there any indication about the length of record used to calculate mean values, frequencies and. other parameters. Although not only the above mentioned users but also European climatologists and agricultural meteorologists will certainly welcome this atlas because of the many new maps presented therein, one cannot avoid the feeling that the authors have shown insuffÉcient scientific preciseness in their presentation of the atlas. This applies both to the explanation of the reasons for the selection of parameters to be mapped and to the defective presentation of the statistical material for the maps. One would like to suggest that a supplement including explanations of the maps and discussions of applications to agriculture be published. It is only fair to the publisher to emphasize that although the choice of some of the colours used is rather debatable, generally speaking the typographical presentation makes the maps quite readable and in some cases also attractive. C. C. WALLEN (Stockholm) A gr. Meteorol., 3 (1966) 263-266
Book Review Agro-climatic Atlas of Europe. (Vol. 1 of a three-volume work: Agroecological Atlas of Cereal Growing in Europe.) P. THRAN and S. BROE~HUIZEN.Pudoc, Wageningen--Elsevier, Amsterdam, 1965, 294 pp., 128 maps, Dfl.95.00, £ 9.10.0. The first volume of an atlas-series called Agroecological Atlas of Cereal Growing in Europe has recently appeared under the heading: Agro¢limatie atlas of Europe. The volume is prepared by Dr. P. Thran from Kiel and Mr. S. Broekhuizen from Wageningen, both well-known specialists in the application of weather data to studies of agricultural potentialities. The series is published by Elsevier Company, Amsterdam. In connection with a review of an agro-climatic atlas of this kind, it might be worthwhile first to consider for a moment the definition of agro-climatology and those methods which should preferably be applied in this field. First of all we must remember that there is a difference between agro-meteorology and agro-climatology as in a similar way between meteorology and climatology. Agro-meteorology is the overall subject aiming at investigating the nature of the physical processes in the air which are related to the development of agricultural species. These physical processes are basically observed by measurements at ordinary meteorological stations of various elements such as radiation, temperature, evaporation, precipitation etc. The data obtained may be used for a direct correlation with simultaneous phenological observations of plant development in order to understand the interrelation between the physical and the physiological processes. However, such observations usually are not very well suited for this application, taken as they are at a height of 2 m above the ground and not in the air layer which is directly in contact with the plants. Moreover, it is not possible to consider the influence of turbulence processes on plant development by the use of such macro-meteorological data. Therefore the micro-meteorological approach has become particularly useful in agro-meteorology as the relevant elements with such an approach are observed in the lowest air layers of the atmosphere which are in direct contact with the plant. By observations of the gradients of various elements with height, the turbulence aspect may also be considered. The application of micro-meteorological data to plant development has often been referred to as micro-climatology or agro-climatology, but as will be clear from the definition of these terms given below this can not be so. Ordinary meteorological observations at a height of 2 m above the ground, although not very suitable for direct studies of the physical processes at plant-level are, however, quite useful for the climatological approach to agricultural problems. This approach implies a statistical treatment of the variation in time and space of meteorological and phenological data aiming at establishing empirically, but not by processes, the existing interrelations between meteorological factors and plant development. Consequently agro-climatology works with parameters such as mean values, frequencies, intensities, dependencies and probabilities of meteorological elements selected and calculated for periods of time so as to suit the study of inter-
Agr. Meteorol., 3 (1966) 263-266
264
BOOKREVIEW
relations with plant-development. The space aspect of this kind of statistics is usually taken into consideration by mapping these parameters for the periods applied and using them for some sort of agro-climatic classification of landareas. Of course micro-meteorological data may also be treated statistically for periods suitable for understanding the relationship with plant development. Furthermore approximative or empirical equations may be derived to determine statistical values of various elements over longer periods of time. Such treatments of micro-meteorological data, but only these, should be considered as part of agro-climatology rather than agro-meteorology. The above definitions seem to imply that the most suitable approach to the whole subject of agro-meteorology would be to establish first of all the interrelationship between physical and physiological processes and only later to calculate and map the climatological parameters when parameters and periods of time may be selected in view of the results obtained by the physical approach. The climatological approach was taken up long before the physical one, due to its much easier application and consequently it has given a considerable amount of results which have been very useful throughout the years. It must be kept in mind, however, that recently so many advanced studies of the physical processes in relation to plant physiology have taken place that modern agro-climatology should now, as far as possible, take results from those studies into consideration. In other words we are now better equipped than earlier to decide which parameters are useful for agroclimatological treatments, taking into consideration the results obtained in investigations with a physical approach to the subject. In his introduction to the atlas under review, Dr. Thran has outlined quite clearly that the intention of the atlas is to outline the climatological foundations for European agriculture. This task, of course, is a typically agro-climatological one in accordance with the definitions given above. The first question that arises in this connection is that asking which elements should be mapped to present an adequate outline. It seems possible that in this selection a more modern approach making use of our knowledge of the physical processes might have been useful. On the other hand there is no doubt that the vast majority of the maps presented are valuable and essential as an adequate basis for the outline. Lack of space does not allow me to discuss those maps which can be accepted as essential, so I shall only bring up for discussion some of them which seem questionable to me. The first map to be discussed is the one showing agro-climatic sub-provinces in Europe. First of all it is doubtful whether the provinces, which have resulted from a rather peculiar method of mixing all boundaries known from various classifications of climate in Europe, may be called agro-climatic. As far as it is possible to judge from the very brief text on the method, there is no clear interrelation between the climatic parameters applied and agricultural conditions. Therefore the result of this "mixing of classifications" is a new climatic classification where the provinces show similarities with regard to various climatic parameters which from the agricultural Agr. Meteorol., 3 (1966) 263-266
BOOK REVIEW
265
point of view seem arbitrarily chosen. There are many other parameters mapped in the atlas which seem much more relevant for a classification than those chosen from K6ppen, Hettner, Blair, etc. For instance the use of those parameters showing climatic conditions during the growing season as well as frequencies, intensities and water balance conditions would have given a more sophisticated classification. The selected method has given us a simplified climatic picture of Europe which is based only on primary and fundamental climatic parameters. It may be useful to agriculturists without being in my opinion particularly suitable to them. It should be added that this climatic classification can hardly be accepted by modern climatologists who would like to see climate classified by means of parameters which give a clear idea of the physical processes involved. A modern classification should, in other words, be based on the genesis of climate, i.e., should be derived from the general circulation of the atmosphere or from other parameters which give a clear picture of the space and time variations in physical processes of the atmosphere. As far as the practical usefulness of the classification is concerned, it seems probable that it would also have increased considerably if a clear description of the reason for selecting the parameters and of their possible interrelation with agriculture could have been added in the text. As to the map itself, it may be noted that the grey colours are too much alike and difficult to separate from each other. Proceeding now to the maps showing numerical values of various parameters derived for basic climatic elements such as temperature, precipitation and evapotranspiration there can be no disagreement that they on the whole represent an excellent contribution which will be most useful to various aspects of applied climatology. In many cases new maps with data never presented earlier are given in this atlas. However, here again one wonders why there is no accompanying text where indications could have been given about how to apply these parameters to agriculture, i.e., again to explain the basic agro-meteorological reasons for the selection of just these parameters. Anybody who is not very familiar with agro-climatology will put this question and unfortunately will not get any answer. Another question that most users of this atlas will put is why no isolines are drawn on the maps. Most problems facing the agriculturist will be to which extent a certain value given on these maps is representative to the surroundings of the place where the value is derived. A climatologist certainly has better qualifications to judge about the representativeness than anybody else. The most suitable and simplest way for him to give an indication of the influence of topography and other geographical complications is to draw isolines for certain threshold values. Such isolines therefore would have increased the value of the atlas considerably. I should like to question a few reasons for some of the maps presented. For example, what is the reason for including a map of the difference between average monthly maximum of the warmest month and average monthly minimum of the coldest month when two more useful parameters to show the annual amplitude of monthly mean temperatures of the air are already given. There is no indication, as far as I know, that this difference as such has any agricultural implication.
Agr. Meteorol.,3 (1966) 263-266
266
BOOK REVIEW
It is a pity that no values of precipitation days were available for all Scandinavia. With some luck the authors could have obtained these values from the meteorological services in the Nordic countries where they are certainly available. Map 371, showing a general survey of the average annual potential evapotranspiration in Europe, is an important contribution to this atlas as it maps a parameter which we know now is essential to agriculture. It is taken from a publication by Mohrmann and Kessler who have studied the water deficiencies in Europe by means of Turc's formula. However, the reviewer has not been able to ascertain whether it is really the potential evapotranspiration which is mapped as said in the title or rather the actual evapotranspiration. There is no doubt that the formula by Turc given on the map generally gives the actual evapotranspiration but with a certain fixed value of the crop factor V it gives the potential evapotranspiration. Without an accompanying explanation it is here again impossible to understand completely the intentions of the authors. Either if this map gives the potential or actual annual evapotranspiration, it would have been worthwhile to apply the formula to some more stations as the map, as it is now, gives too few details, particularly for the northern part of Europe. A general comment on the maps reproduced from Mohrmann and Kessler's work is that they are difficult to understand, and interpret without studying the original paper, because in the atlas there is no indication or text about how water deficiency is defined and calculated. As emphasized earlier, this last comment could be generalized to apply to the whole atlas and it seems to include a rather serious criticism. The authors obviously have thought that by presenting their maps in an atlas intended above all for statisticians and agriculturists who are not specialists in climatology, there was no need for clear explanations to be given about how the maps were prepared. This seems a serious mistake because as they are now presented., it is impossible to judge the representativeness and accuracy of the data. There is no discussion about the basic material used for the preparation of the maps, nor is there any indication about the length of record used to calculate mean values, frequencies and. other parameters. Although not only the above mentioned users but also European climatologists and agricultural meteorologists will certainly welcome this atlas because of the many new maps presented therein, one cannot avoid the feeling that the authors have shown insuffÉcient scientific preciseness in their presentation of the atlas. This applies both to the explanation of the reasons for the selection of parameters to be mapped and to the defective presentation of the statistical material for the maps. One would like to suggest that a supplement including explanations of the maps and discussions of applications to agriculture be published. It is only fair to the publisher to emphasize that although the choice of some of the colours used is rather debatable, generally speaking the typographical presentation makes the maps quite readable and in some cases also attractive. C. C. WALLEN (Stockholm) A gr. Meteorol., 3 (1966) 263-266